Pending Policies - Surgery


Intracranial Stenting or Angioplasty, including Endovascular Procedures

Number:SUR701.027

Effective Date:04-15-2018

Coverage:

*CAREFULLY CHECK STATE REGULATIONS AND/OR THE MEMBER CONTRACT*

Acute Ischemic Stroke

Endovascular intra-arterial mechanical embolectomy or thrombectomy may be considered medically necessary in the treatment of acute ischemic stroke when the following criteria have been met:

Angiographic studies have confirmed proximal arterial occlusion of the anterior circulation of the brain, in any of the following anterior intracranial arteries:

1. Intracranial carotid; OR

2. Middle cerebral artery (M1 or M2); OR

3. Anterior cerebral artery (A1 or A2); AND

Neuroimaging is consistent with early ischemic change, without hemorrhage; AND

Intra-arterial mechanical embolectomy is performed within 6 hours of onset of symptoms; AND

NIH (National Institutes of Health) Stroke Scale (NIHSS) score of 2 or greater; AND

CT (computed tomography) or MRI (magnetic resonance imaging) scan has ruled out intracranial hemorrhage or arterial dissection.

NOTE 1: Retrievable stents used for mechanical embolectomy include, Merci® Retriever, Penumbra System®, Solitaire™ Flow Restoration Device, or the Trevo® Retriever Devices. (Refer to the Regulatory Status within Description for a listing of all devices addressed in this policy.)

Endovascular interventions, such as intra-arterial mechanical embolectomy, thrombectomy, angioplasty or non-retrievable stenting, are considered experimental, investigational and/or unproven when the above criteria are not met.

Atherosclerotic Cerebrovascular Disease

Intracranial percutaneous transluminal angioplasty (PTA), with or without stenting, is considered experimental, investigational and/or unproven in the treatment of atherosclerotic cerebrovascular disease (CVD).

Cerebral Aneurysms

Intracranial stent placement may be considered medically necessary as part of the endovascular treatment of intracranial/cerebral aneurysms when surgical treatment is not appropriate AND standard endovascular techniques do not allow for complete isolation of the aneurysm, such as a wide-neck aneurysm (4 mm or more) or a sack-to-neck ratio less than 2:1.

Intracranial flow-diverting stents with the U.S. Food and Drug Administration (FDA) approval for the treatment of intracranial aneurysms may be considered medically necessary as part of the endovascular treatment of intracranial aneurysms that are not amenable to surgical treatment or standard endovascular therapy AND meet the following anatomic criteria:

Large or giant wide-necked intracranial aneurysms, with a size of 10 mm or more and a neck diameter of 4 mm or more, in the internal carotid artery from the petrous to the superior hypophyseal segments.

Intracranial stent placement is considered experimental, investigational and/or unproven in the treatment of intracranial aneurysms except as noted above.

NOTE 2: This policy only addresses endovascular therapies used on intracranial vessels.

NOTE 3: These policy statements are not intended to address the use of rescue endovascular therapies, including intra-arterial vasodilator infusion and intracranial percutaneous transluminal angiography, in delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage.

Description:

Intracranial arterial disease includes thromboembolic events, vascular stenoses, and aneurysms. Endovascular techniques have been investigated for treatment of intracranial arterial disease. Endovascular therapy is used as an alternative or adjunct to intravenous (IV) tissue plasminogen activator (tPA; IV-tPA) and supportive care for acute stenosis and as an adjunct to risk-factor modification for chronic stenosis. For cerebral aneurysms, stent-assisted coiling and the use of flow-diverting stents have been evaluated as an alternative to endovascular coiling in patients whose anatomy is not amenable to simple coiling.

Background

Cerebrovascular diseases (CVDs) include a range of processes affecting the cerebral vascular system, including arterial thromboembolism, arterial stenosis, and arterial aneurysms, all of which can restrict cerebral blood flow due to ischemia or hemorrhage. Endovascular techniques, including endovascular mechanical embolectomy with various devices (i.e., stents), and angioplasty with or without stenting have been investigated for treatment of CVDs.

Acute Stroke

Acute stroke is the third leading cause of death in the U.S., Canada, Europe, and Japan; it is the leading cause of adult disability in the U.S. (1) Eighty-seven percent of strokes are ischemic and 13% hemorrhagic. Differentiation between the 2 types of stroke is necessary to determine the appropriate treatment. Ischemic stroke occurs when an artery to the brain is blocked by a blood clot, which forms in the artery (thrombotic), or when another substance (i.e., plaque, fatty material) travels to an artery in the brain causing a blockage (embolism). Recanalization of the artery, particularly in the first few hours after occlusion, reduces rates of disability and death. (2)

The prompt use of IV thrombolytic therapy with recombinant tPA to recanalize occluded blood vessels has been associated with improved outcomes in multiple randomized controlled trials (RCTs) and meta-analyses. (3) Therefore, use of IV-tPA in ischemic stroke patients presenting within 3 hours (up to 4.5 hours in some cases) of stroke onset in expert centers is recommended.

Despite the potential benefits of IV-tPA in eligible patients who present within the appropriate time window, limitations to reperfusion therapy with IV-tPA have prompted investigations of alternative acute stroke therapies. These limitations include:

Requirement for treatment within 4.5 hours of stroke onset. Relatively few patients present for care within the time window in which tPA has shown benefit. In addition, determining the time of onset of symptoms is challenging in patients awakening with symptoms of acute stroke; patients with symptoms on awakening are considered to have symptom onset when they went to sleep. In 2010 to 2011, fewer than 10% of all ischemic stroke patients arrived at the hospital and received IV-tPA within the 3-hour window. (4)

Risks associated with IV-tPA therapy. tPA is associated with increased risk of intracranial bleeding. It is contraindicated in hemorrhagic stroke and in some ischemic stroke patients for whom the risk of bleeding outweighs the potential benefit, such as those with mild or resolving symptoms, hypocoagulable state, or advanced age.

Variable recanalization rates. For patients receiving tPA, recanalization rates are around 21% and range from about 4% in the distal internal carotid artery and basilar artery to about 32% in the middle cerebral artery. (5) The treatment of large vessel strokes with IV-tPA may be less successful.

Researchers have studied intra-arterial tPA, transcranial ultrasound energy, and mechanical clot destruction or clot removal as alternatives or second lines to the established IV-tPA therapy.

Several types of endovascular treatments for ischemic strokes have been used:

Intra-arterial fibrinolytic therapy (i.e., intra-arterial tPA). Although tPA only has approval from the U.S. Food and Drug Administration (FDA) for its intravenous route of delivery, intra-arterial tPA has been considered for patients who fail to present within the window of treatment for intravenous tPA or who have failed to show benefit from intravenous tPA. It is also frequently used in conjunction with other endovascular devices.

Acute angioplasty and/or stent deployment. Balloon angioplasty and balloon-expandable stents have been investigated for acute stroke. Given concern for higher risks of complications in the cerebral vasculature with the use of balloon-expandable stents, self-expanding stents have gained more attention. At present, no balloon- or self-expandable stent has FDA approval for treatment of acute stroke.

Endovascular mechanical embolectomy. Endovascular embolectomy devices remove or disrupt clots by a number of mechanisms. Four devices have FDA approval for treatment of acute stroke (see Regulatory Status section): The Merci® Retriever, Penumbra System®, Solitaire™ Flow Restoration Device, and the Trevo® Retriever. With the Merci® device, a microcatheter is passed through the thrombus from a larger, percutaneous catheter positioned proximal to the occlusion. A helical snare is deployed, and the catheter and clot are withdrawn together. With the Penumbra® device, an opening at the tip of the percutaneous catheter uses suction to extract the clot. Both the Solitaire Flow Restoration Device and the Trevo Retriever are retrievable stents, which are positioned to integrate the clot with the stent for removal with the stent’s struts.

This policy review focuses on the devices listed above with an indication for endovascular embolectomy for acute stroke. Additional retrievable stent devices are under investigation, such as the Embolus Retriever with Interlinked Cages (ERIC; MicroVention, Tustin, CA). (6)

An additional clinical situation in which endovascular therapies may be used in the treatment of acute ischemic stroke is in the setting of cerebral vasospasm following intracranial (subarachnoid) hemorrhage. Delayed cerebral ischemia (DCI) occurs about 3 to 14 days after the acute bleed in about 30% of patients experiencing subarachnoid hemorrhage and is a significant contributor to morbidity and mortality in patients who survive the initial bleed. In cases refractory to medical measures, rescue invasive therapies including intra-arterial vasodilator infusion therapy (e.g., calcium channel blockers) and transluminal balloon angioplasty may be used. (7, 8) The mechanism of disease, patient population, and time course of therapy differ from DCI occurring after subarachnoid hemorrhage compared with ischemic stroke due to atheroembolic disease. Therefore, this indication for endovascular intervention will not be addressed in this policy.

Intracranial Atherosclerotic Disease

It is estimated that intracranial atherosclerosis causes about 8% of all ischemic strokes. Intracranial stenosis may contribute to stroke in 2 ways: either due to embolism or low-flow ischemia in the absence of collateral circulation. Recurrent annual stroke rates are estimated at 4% to 12% per year with atherosclerosis of the intracranial anterior circulation and 2.5% to 15% per year with lesions of the posterior (vertebrobasilar) circulation. Medical treatment typically includes either anticoagulant therapy (i.e., warfarin) or antiplatelet therapy (e.g., aspirin). The Warfarin-Aspirin Symptomatic Intracranial Disease (WASID) trial assessed the incidence of stroke brain hemorrhage or death among patients randomized to receive aspirin or warfarin. The trial found that over a mean 1.8 years of follow-up, warfarin provided no benefit over aspirin and was associated with a significantly higher rate of complications. In addition, if symptoms could be attributed to low-flow ischemia, agents to increase mean arterial blood pressure and avoidance of orthostatic hypotension may be recommended. However, medical therapy has been considered less than optimal. For example, in patients with persistent symptoms despite antithrombotic therapy, the subsequent rate of stroke or death has been extremely high, estimated in 1 study at 45%, with recurrent events within 1 month of the initial event. Surgical approaches have met with limited success. The widely cited extracranial-intracranial (EC/IC) bypass study randomized 1377 patients with symptomatic atherosclerosis of the internal carotid or middle cerebral arteries to medical care or EC/IC bypass. Outcomes in the 2 groups were similar, suggesting that the EC/IC bypass is ineffective in preventing cerebral ischemia. Due to inaccessibility, surgical options for the posterior circulation are even more limited.

Percutaneous transluminal angioplasty (PTA) has been approached cautiously for use in intracranial circulation, due to technical difficulties in catheter and stent design and the risk of embolism, which may result in devastating complications if occurring in the posterior fossa or brain stem. However, improvement in the ability to track catheterization, allowing catheterization of tortuous vessels, and the increased use of stents have created ongoing interest in PTA as a minimally invasive treatment of this difficult-to-treat population. Most published studies of intracranial PTA have focused on vertebrobasilar circulation. Two endovascular devices have FDA approval for treatment of symptomatic intracranial stenosis and are considered here (see Regulatory Status section).

Cerebral Aneurysms

Compared with acute ischemic stroke, cerebral aneurysms have a much lower incidence among the U.S., with prevalence between 0.5% and 6% of the population. (9) However, they are associated with significant morbidity and mortality due to subarachnoid hemorrhage resulting from aneurysm rupture. Surgical clipping of intracranial aneurysms has been used since the 1960s, but the feasibility of clipping for aneurysms depends on the aneurysm location. Intracranial stents are also being used to treat cerebral aneurysms. Stent-assisted coiling began as an approach to treat fusiform or wide-neck aneurysms in which other surgical or endovascular treatment strategies may not be feasible. As experience has grown, stenting has also been used in smaller berry aneurysms as an approach to decrease the rate of retreatment needed in patients who receive coiling. A randomized trial has demonstrated that treatment of ruptured intracranial aneurysms with coiling leads to improved short-term outcome compared with surgical clipping; however, patients who receive coiling need more repeat/follow-up procedures.

In 2011, the Pipeline® Embolization Device, which falls into a new device category called “intracranial aneurysm flow diverters,” or flow-diverting stent, received FDA premarket approval (PMA) for endovascular treatment of large or giant wide-necked intracranial aneurysms in the internal carotid artery. The Pipeline device is a braided, wire mesh device that is placed within the parent artery of an aneurysm to redirect blood flow away from the aneurysm, with the goal of preventing aneurysm rupture and possibly decreasing aneurysm size.

Other flow-diverting or flow-disrupting devices are under development or in use outside the U.S. Other flow-diverters are the FRED system (MicroVention, Tustin, CA), the Silk device (Balt Extrusion, Montmorency, France), the Surpass Streamline Flow Diverter (Stryker, Kalamazoo, MI), and the p64 Flow Modulation Device (Phenox, Bochum, Germany).

The Woven EndoBridge aneurysm embolization system (Sequent Medical, Aliso Viejo, CA) is an intravascular flow disrupter that is designed to bridge the neck of an aneurysm. The device is under evaluation in a U.S. investigational device exemption clinical study (WEB-IT).

In addition to the development of flow-diverting stents, several low-profile self-expandable intracranial stents are in various stages of development: LEO Baby (Balt Extrusion, Montmorency, France) and LVIS Jr (MicroVention, Tustin, CA). At least 1 retrievable self-expanding stent is available in Europe for the treatment of aneurysms, the Solitaire AB device (Covidien [now Medtronic], Plymouth, MN).

Finally, at least 2 devices designed to treat aneurysms at vessel bifurcations are CE (Conformité Européenne, meaning European Conformity) marked in Europe, but not available in the U.S.: the pCONus Bifurcation Aneurysm Implant (MicroVention, Tustin, CA) and the PulseRider (Pulsar Vascular, San Jose, CA).

Patient Selection for Endovascular Mechanical Embolectomy for Acute Ischemic Stroke

The major RCTs demonstrating a benefit with endovascular mechanical embolectomy vary in criteria for selecting patients based on the presence or absence of salvageable brain tissue. Several RCTs use the Alberta Stroke Program Early Computed Tomography Score (ASPECTS), which is a 10-point quantitative computed tomography (CT) score to assess the presence of early ischemic changes. MR CLEAN (Berkhemer et al., 2015 [16]) did not specify imaging criteria to demonstrate salvageable brain tissue. The following criteria were used by other trials (descriptions of trial names can be found in the Rationale of this policy):

REVASCAT Trial (Jovin et al., 2015[20]). Exclusion criteria were as follows: Hypodensity on CT or restricted diffusion demonstrated by:

o An ASPECTS score of less than 7 on CT, CT perfusion cerebral blood volume (CBV), computed tomography angiography (CTA) source imaging; OR

o An ASPECTS score of less than 6 on diffusion-weighted imaging (DWI) magnetic resonance imaging (MRI).

ESCAPE Trial (Goyal et al., 2015 [17]). Exclusion criteria were as follows:

Baseline non-contrast CT with extensive early ischemic changes of ASPECTS 0 to 5 in the territory of symptomatic intracranial occlusion; OR

o Other confirmation of a moderate-to-large core defined 1 of 3 ways:

1. On a single phase, multiphase, or dynamic CTA: no or minimal collaterals in a region greater than 50% of the middle cerebral artery (MCA) territory when compared with pial filling on the contralateral side (multiphase/dynamic CTA preferred); OR

2. On CT perfusion (>8 cm coverage): a low CBV and very low cerebral blood flow (CBF), ASPECTS less than 6 AND in the symptomatic MCA territory; OR

3. On CT perfusion (<8 cm coverage): a region of low CBV and very low CBF greater than one-third of the CT perfusion-imaged symptomatic MCA territory.

EXTEND-IA Trial (Campbell et al., 2015 [18]). Inclusion criteria were based on CT perfusion imaging using CT or MRI with a T-max more than 6-second delay perfusion volume and either CT regional CBF or DWI infarct core volume as follows:

o Mismatch ratio greater than 1.2; AND

o Absolute mismatch volume greater than 10 mL; AND

o Infarct core lesion volume less than 70 mL.

SWIFT PRIME Trial (Saver et al., 2015 [40]). Exclusion criteria related to imaging-demonstrated core infarct and hypoperfusion:

o MRI-assessed core infarct lesion greater than:

1. 50 cm3 for subjects age 18 to 79 years;

2. 20 cm3 for subjects age 80 to 85 years;

o CT-assessed core infarct lesion greater than:

1. 40 cm3 for subjects age 18 to 79 years;

2. 15 cm3 for subjects age 80 to 85 years;

o For all subjects, severe hypoperfusion lesion (≥-10-second T-max lesion >100 cm3);

o For all subjects, ischemic penumbra of 15 cm3 or more and mismatch ratio greater than 1.8.

The RCTs demonstrating a benefit to endovascular mechanical embolectomy in acute stroke generally had some inclusion criteria to reflect stroke severity, with the exception of the EXTEND-IA trial. The REVASCAT and ESCAPE trials both required a baseline (post-stroke) National Institutes of Health Stroke Scale (NIHSS) score of 6 or higher. MR CLEAN specified a clinical diagnosis of acute stroke with a deficit on the NIHSS score of 2 points or more. SWIFT PRIME specified an NIHSS score of 8 or more and less than 30 at the time of randomization.

Flow-diverting stents are indicated for the treatment of large or giant wide-necked intracranial aneurysms, with a size of 10 mm or more and a neck diameter of 4 mm or more, in the internal carotid artery from the petrous to the superior hypophyseal segments.

Common Assessments of Stroke or Disability Impairments

National Institute of Health Stroke Scale (NIHSS)

The NIHSS is a tool used by healthcare providers to objectively quantify the impairment caused by a stroke. (153) The NIHSS is composed of 11 items, each of which scores a specific ability between a 0 and 4. For each item, a score of 0 typically indicates normal function in that specific ability, while a higher score is indicative of some level of impairment. The individual scores from each item are summed in order to calculate a patient's total NIHSS score. The maximum possible score is 42, with the minimum score being a 0. The 11 items accessed are level of consciousness, horizontal eye movement, visual field test, facial palsy, motor arm, motor leg, limb ataxia, sensory, language, speech, and inattention. The following is a description of each NIHSS level:

Score of 0 = No Stroke Symptoms

Score of 0-4 = Minor Stroke

Score of 5-15 = Moderate Stroke

Score of 16-20 = Moderate to Severe Stroke

Score of 21-42 = Severe Stroke.

Modified Rankin Scale (mRS)

The mRS is a commonly used scale for measuring the degree of disability or dependence in the daily activities of people who have suffered a stroke or other causes of neurological disability. It has become the most widely used clinical outcome measure for stroke clinical trials. (154) The following is a description of each mRS score:

1 - No significant disability despite symptoms: able to carry out all usual duties and activities.

2 - Slight disability; unable to carry out all previous activities, but able to look after own affairs without assistance.

3 - Moderate disability; requiring some help, but able to walk without assistance.

4 - Moderately severe disability; unable to walk without assistance and unable to attend to own bodily needs without assistance.

5 - Severe disability; bedridden, incontinent and requiring constant nursing care and attention.

6 - Dead.

Regulatory Status

Several devices for endovascular treatment of intracranial arterial disease were cleared for marketing by the FDA through the 510(k) process or the humanitarian device exemption (HDE) process. By indication, approved devices are as follows.

Acute Stroke

Merci® Retriever

In August 2004, the Merci® Retriever (Concentric Medical, Mountain View, CA) was cleared for marketing by FDA through the 510(k) process. This device was judged equivalent to a predicate device, the Concentric Retriever, which was indicated for endovascular foreign body removal. FDA clearance indicated that the Mechanical Embolus Removal in Cerebral Ischemia (MERCI) Clinical Study established that no new issues of safety or effectiveness exist when the Merci® Retriever is used for thrombus removal versus foreign body removal from the neurovasculature. In May 2006, a modified Merci® Retriever, also manufactured by Concentric Medical, was cleared for marketing by FDA through the 510(k) process. The clearance notes that the Modified Merci® Retriever is intended to restore blood flow in the neurovasculature by removing thrombus in patients experiencing ischemic stroke. Patients who are ineligible for IV-tPA or who fail IV-tPA therapy are candidates for treatment. The device also has clearance for retrieval of foreign bodies misplaced during interventional radiologic procedures in the neuro-, peripheral, and coronary vasculature. FDA product code: NRY.

The Penumbra System®

In December 2007, the Penumbra System® (Penumbra, Alameda, CA) was cleared for marketing by FDA through the 510(k) process. FDA determined that this device was substantially equivalent to existing devices for use in the revascularization of patients with acute ischemic stroke secondary to intracranial large vessel occlusive disease (in the internal carotid, middle cerebral [Ml and M2] segments, basilar, and vertebral arteries) within 8 hours of symptom onset. FDA product code: NRY.

Solitaire™ FR

In March 2012, the Solitaire™ FR device (Covidien/ev3 Neurovascular, Irvine, CA) was cleared for marketing by FDA through the 510(k) process. FDA determined that this device was substantially equivalent to the Merci® Retriever device, based on a randomized controlled trial (RCT), of 113 patients, submitted to FDA comparing the Merci® and Solitaire™ devices. Indications for the device are patients with ischemic stroke due to large intracranial vessel occlusion who are ineligible for intravenous tPA, or who fail intravenous tPA. FDA product code: NRY.

Trevo® Pro Retriever

In August 2012, the Trevo® Pro Retriever device (Stryker Neurovascular, Kalamazoo, MI) was cleared for marketing by FDA through the 510(k) process. FDA determined that this device was substantially equivalent to the Merci® Retriever device, based on an RCT of 178 patients from 27 centers in the U.S. and Europe that compared the Trevo® device with the Merci® device. Indications for the device are patients with acute ischemic stroke due to large intracranial vessel occlusion who are ineligible for or fail intravenous tPA. Later versions of the Trevo® Retriever are called the Modified Trevo® Retriever, the Trevo® ProVue Retriever, and the Modified Trevo® ProVue Retriever. On September 2, 2016, the FDA approved the Trevo® ProVue and XP ProVue Retrievers as Class II devices, which are substantially equivalent devices of generic type. Under Class II, the generic name is “Neurovascular Mechanical Thrombectomy Device for Acute Ischemic Stroke Treatment.” Earlier in 2015, the FDA had approved these devices as Class III. To minimize confusion, the name Trevo® Retriever or Trevo® is used throughout this review. FDA product code: NRY.

Table 1 summarizes the devices with FDA clearance for the endovascular treatment of acute stroke.

Table 1: FDA-Cleared Mechanical Embolectomy Devices for Acute Stroke

Device

Approval Date

Indications

Merci® Retriever (Concentric Medical, Mountain View, CA; acquired by Stryker Neurovascular, Kalamazoo, MI, in 2011)

Aug 2004 (modified device approved May 2006)

Patients with acute ischemic stroke and who are ineligible for or who fail IV-tPA therapy

Penumbra System® (Penumbra, Alameda, CA)

Dec 2007

Patients with acute ischemic stroke secondary to intracranial large vessel occlusive disease within 8 hours of symptom onset

Stent Retrievers

Solitaire™ FR Revascularization Device Covidien/ev3 Neurovascular, Irvine, CA)

Mar 2012

Patients with acute ischemic stroke due to large intracranial vessel occlusion who are ineligible for or who fail IV-tPA

Trevo® Retriever device (Stryker Neurovascular, Kalamazoo, MI)

Oct 2012

Patients with acute ischemic stroke due to large intracranial vessel occlusion who are ineligible for or who fail IV-tPA

Trevo® Pro Retriever (includes Trevo® ProVue and XP ProVue Retrievers) (Stryker Neurovascular, Kalamazoo, MI)

May 2012 (modified Class designation Sep 2016)

Patients experiencing ischemic stroke within 6 hours of symptom onset and following the administration of IV-tPA within 3 hours of symptom onset

Table Key:

FDA: U.S. Food and Drug Administration;

IV: intravenous;

tPA: tissue plasminogen activator.

Intracranial Stenosis

Two devices were approved by FDA through the HDE process for atherosclerotic disease. This form of FDA approval is available for devices used to treat conditions with fewer than 4000 incidents per year; the FDA only requires data showing “probable safety and effectiveness.” Devices with their labeled indications are as follows.

Neurolink System®

“The Neurolink system [Guidant, Santa Clara, CA] is indicated for the treatment of patients with recurrent intracranial stroke attributable to atherosclerotic disease refractory to medical therapy in intracranial vessels ranging from 2.5 to 4.5 mm in diameter with ≥50% stenosis and that are accessible to the stent system.”

Wingspan™ Stent System

“The Wingspan Stent System [Boston Scientific, Fremont, CA] with Gateway PTA Balloon Catheter is indicated for use in improving cerebral artery lumen diameter in patients with intracranial atherosclerotic disease, refractory to medical therapy, in intracranial vessels with ≥50% stenosis that are accessible to the system.”

Intracranial Aneurysms

In 2011, the Pipeline® Embolization Device (Covidien/eV3 Neurovascular, Irvine, CA), an intracranial aneurysm flow diverter, was approved by FDA through the PMA process for the endovascular treatment of adults (≥22 years) with large or giant wide-necked intracranial aneurysms in the internal carotid artery from the petrous to the superior hypophyseal segments (P100018). (10) Approval was based on the Pipeline for Uncoilable for Failed Aneurysms Study, a single-arm, open-label feasibility study that included 108 patients, ages 30 to 75 years, with unruptured large and giant wide-necked aneurysms. (11)

Three stents have been approved by FDA through the HDE program process for treatment of intracranial aneurysms. Stents with their labeled indications are as follows.

Neuroform™ Microdelivery Stent System

In 2002, based on a series of approximately 30 patients with 6-month follow-up, the Neuroform Microdelivery Stent System (Stryker, Kalamazoo, MI) was approved by FDA through the HDE process for use with embolic coils for treatment of wide-neck intracranial aneurysms that cannot be treated by surgical clipping (H020002).

Enterprise™ Vascular Reconstruction Device and Delivery System

In 2007, based on a series of approximately 30 patients with 6-month follow-up, the Enterprise™ Vascular Reconstruction Device and Delivery (Cordis Neurovascular, Miami Lakes, FL) was approved by FDA through the HDE process for use with embolic coils for treatment of wide-neck, intracranial, saccular or fusiform aneurysms (H060001).

The Low-Profile Visualized Intraluminal Support Device

In July 2014, the Low-Profile Visualized Intraluminal Support Device (LVIS™ and LVIS™ Jr.) (MicroVention, Tustin, CA) was approved by FDA through the HDE process (H130005) for use with embolic coils for the treatment of unruptured, wide neck (neck, ≥4 mm or dome to neck ratio, <2), intracranial, saccular aneurysms arising from a parent vessel with a diameter of 2.5 mm or greater and 4.5 mm or smaller.

Rationale:

This policy was created in September 2012 (from an archived policy originally created in January 1993, updated periodically with literature reviews as part of Medical Policy MED202.032 – Stenting for Vascular Occlusive Disease, and can be located as an Archived Document at the end of this policy). The most recent literature search for this policy (SUR701.027) was performed for the period through October 21, 2016. The following is a summary of the key literature to date.

Assessment of efficacy for therapeutic intervention involves determining whether the intervention improves health outcomes. The optimal study design for this purpose is a randomized controlled trial (RCT) that includes clinically relevant measures of health outcomes. Intermediate outcome measures, also known as surrogate outcome measures, may also be adequate if there is an established link between the intermediate outcome and true health outcomes. Nonrandomized comparative studies and uncontrolled studies can sometimes provide useful information on health outcomes but are prone to biases such as noncomparability of treatment groups, placebo effect, and variable natural history of the condition.

Clinical Trial Name Vocabulary

CAVATAS: Carotid And Vertebral Artery Transluminal Angioplasty Study.

CASSISS: China Angioplasty & Stenting for Symptomatic Intracranial Severe Stenosis.

DIVERT: Diversion of Flow in Intracranial VErtebral and Blood Blister-like Ruptured Aneurysms Trial.

EARLY: Endovascular Arterial Reperfusion versus Intravenous ThromboLYsis for Acute Ischemic Stroke Study.

EASI: Endovascular Acute Stroke Intervention Trial.

ESCAPE Trial: Evaluation Study of Congestive Heart Failure And Pulmonary Artery Catheterization Effectiveness Trial.

EVIDENCE: Flow Diverter Stent for Endovascular Treatment of Unruptured Saccular Wide-necked Intracranial Aneurysms Study.

EXTEND-IA Trial: EXtending the Time for Thrombolysis in Emergency Neurological Deficits – Intra-Arterial Trial.

FIAT: Flow Diversion in Intracranial Aneurysm Treatment.

IMS III: Interventional Management of Stroke 3 Trial.

LARGE: LARGE Aneurysm Randomized Trial.

MAPS: Matrix And Platinum Science Trial.

MERCI: Mechanical Embolus Removal in Cerebral Ischemia Study.

MELT Trial: Middle Cerebral Artery Embolism Local Fibrinolytic Intervention Trial.

MR CLEAN Trial: Multicenter Randomized CLinical trial of Endovascular treatment for Acute ischemic stroke in The Netherlands.

MR RESCUE: Mechanical Retrieval and REcanalization of Stroke Clots Using Embolectomy.

NINDS tPA Stroke Study: National Institute of Neurological Disorders and Stroke rt-PA Stroke Study Group.

POSITIVE: Perfusion Imaging Selection of Ischemic Stroke Patients for Endovascular Therapy.

PROACT II: PROlyse in Acute Cerebral Thromboembolism II.

PUFA: Pipeline for Uncoilable or Failed Aneurysms.

RESILIENT: EndoVascular Treatment with Solitaire™ FR versus. Best Medical Therapy in Acute Ischemic Stroke.

RESTORE: RECO Flow Restoration Device Versus Intravenous t-PA for Stroke Within 4.5h of Symptom Onset: A Prospective Randomized Control Trial.

REVASCAT Trial: Randomized Trial of REVASCularization with Solitaire™ FR Device Versus Best Medical Therapy in the Treatment of Acute Stroke Due to Anterior Circulation Large Vessel Occlusion Presenting within 8 Hours of Symptom OnseT.

SAMMPRIS: Stenting and Aggressive Medical Management for Preventing Recurrent Stroke in Intracranial Stenosis.

SSYLVIA: Stenting of SYmptomatic atherosclerosis Lesions in the Vertebral or Intracranial Arteries.

STAR Trial: Solitaire™ FR Thrombectomy for Acute Revascularisation.

STAT: Stenting in the Treatment of Aneurysm Trial.

SWIFT: Solitaire™ FR With the Intention For Thrombectomy.

SWIFT-PRIME: Thrombectomy as Primary Endovascular Treatment for Acute Ischemic Stroke.

SYNTHESIS Expansion: Intra-arterial versus Systemic Thrombolysis for Acute Ischemic Stroke.

THERAPY: Assess the Penumbra System® in the Treatment of Acute Stroke Study.

TREVO 2: Thrombectomy REvascularization of Large Vessel Occlusions Study.

VISSIT Trial: Vitesse Intracranial Stent Study for Ischemic Therapy.

VISTA-TREAT: Virtual International Stroke Trials Archive -ThRombEctomy and Tissue Plasminogen ActivaTor.

WASSABI: WAke up Symptomatic Stroke – Benefit of IntrAvenous Clot Busters or Endovascular Interventions Study.

Endovascular Interventions for Acute Ischemic Stroke

Endovascular Interventions for Anterior Circulation Acute Ischemic Strokes

The policy focuses on the available RCTs and other comparative studies.

Systematic Reviews and Meta-Analyses

Multiple systematic reviews and meta-analyses of RCTs evaluating endovascular therapy for acute stroke have been published, with varying inclusion criteria. The most relevant systematic reviews include the results of a series of RCTs published from 2014 to 2015 comparing endovascular therapies with standard care; they are the focus of this review. Some systematic reviews have focused only on mechanical embolectomy, while others have evaluated endovascular therapies more broadly.

In 2015, Badhiwala et al. reported results of a meta-analysis of RCTs evaluating mechanical embolectomy after acute ischemic stroke. (12) Eligible studies were RCTs comparing endovascular therapy with standard care, including the use of intravenous (IV) plasminogen activator (tPA), in adult participants with acute stroke. Eight trials were included (Ciccone et al., [13] Kidwell et al., [14] Broderick et al., [15] Berkhemer et al., [16] Goyal et al., [17] Campbell et al., [18] Saver et al., [19] Jovin et al. [20]), with a total of 2423 patients. (These specific RCTs are described individually below.) Studies were assessed as having low risk of bias overall with the Cochrane Collaboration’s tool. In a meta-analysis, the use of endovascular intervention lead to proportional treatment benefit across modified Rankin Scale (mRS) scores (odds ratio [OR], 1.56; 95% confidence interval [CI], 1.14 to 2.13; p=0.005). Patients treated with endovascular intervention were more likely than standard care patients to have functional independence at 90 days (44.6% for endovascular treatment [95% CI, 36.6% to 52.8%]; 31.8% for standard treatment [95% CI, 24.6% to 40.0%]), with an associated absolute risk difference of 12.0% (95% CI, 3.8% to 20.3%; OR=1.71; 95% CI, 1.18 to 2.49; p=0.005). However, there was significant heterogeneity (I2=75.4%) in the analysis of functional improvement outcomes. The authors conducted a number of sensitivity analyses around predictors of functional outcomes, and found that the following factors were associated with functional outcomes:

Use of angiographic imaging confirming proximal arterial occlusion (OR=2.24; 95% CI, 1.72 to 2.9; p<0.001 for interaction).

Use of IV-tPA and endovascular therapy (OR=2.07; 95% CI, 1.46 to 2.92; p=0.018 for interaction).

Use of stent retriever for mechanical thrombectomy (OR=2.39; 95% CI, 1.88 to 3.04; p<0.001 for interaction).

There were no significant differences between endovascular intervention group and standard care group patients in rates of symptomatic intracranial hemorrhage or death at 90 days.

In a meta-analysis including the same 8 trials included in the Badhiwala study, Chen et al. (21) reported a similar OR for 90-day functional independence as Badhiwala.

Hong et al. conducted a meta-analysis of RCTs comparing endovascular recanalization therapy with standard care in acute ischemic stroke. (22) This analysis included 15 RCTs with a total of 2899 patients, 1575 randomized to endovascular recanalization arms and 1324 to control arms. In addition to the 8 trials which compared mechanical embolectomy with standard care (Ciccone et al., [13] Kidwell et al., [14] Broderick et al., [15] Berkhemer et al., [16] Goyal et al., [17] Campbell et al., [18] Saver et al., [19] Jovin et al. [20]), this meta-analysis also included 2 trials evaluating intra-arterial pro-urokinase, 3 trials evaluating intra-arterial urokinase, 1 evaluating intra-arterial with IV-tPA, and 1 evaluating intra-arterial tPA with mechanical thrombectomy. In a random-effects model including all trials, endovascular recanalization was associated with greater proportions of patients with mRS scores of 0 to 2 (43.3% versus 31.9%; OR=1.79; 95% CI, 1.34 to 2.4; p<0.001). For safety outcomes, when all trials were included, rates of symptomatic intracranial hemorrhage were higher in endovascular recanalization arms, although the between-group difference was not statistically significant (5.8% versus 4.6%; OR=1.19; 95% CI, 0.83 to 1.69; p=0.345).

In another meta-analysis, Kennedy et al. compared local mechanical and/or pharmacologic endovascular therapy, with or without IV thrombolysis, with standard care control that included IV thrombolysis when appropriate. (23) Eleven RCTs were included, the 8 trials comparing mechanical embolectomy with standard care (Ciccone et al., [13] Kidwell et al., [14] Broderick et al., [15] Berkhemer et al., [16] Goyal et al., [17] Campbell et al., [18] Saver et al., [19] Jovin et al. [20]), along with 2 trials comparing intra-arterial tPA with IV-tPA alone, one of which was very small (n=7), and one evaluating intra-arterial tPA with mechanical thrombectomy. In a meta-analysis of all trials, patients in the local endovascular therapy groups had higher rates of functional independence than those treated with standard care (OR=1.78; 95% CI, 1.262 to 2.51; p<0.001). In subanalyses limited to trials that used imaging selection, that used stent retriever devices in at least half of cases, or in which IV-tPA was used in conjunction with endovascular therapy as appropriate, the use of local endovascular therapy remained significantly associated with higher rates of functional independence, with stronger effect sizes than in the overall analysis. However, in a subanalysis limited to trials in which endovascular arm patients did not receive IV tPA, there was no significant between-group difference in 90-day functional independence (OR=1.45; 95% CI, 0.597 to 3.54, p>0.05).

Given the disproportionate benefit associated with stent retriever use in subanalyses of RCTs, there has been some focus on the specific efficacy of stent retrievers for acute stroke.

Bush et al. conducted a meta-analysis of RCTs using predominantly stent retriever devices for acute stroke treatment. (24) Trials that compared endovascular therapy with stent retrievers with medical management (defined as I- tPA unless it was contraindicated) were included. However, it is not specified how the authors defined a threshold to determine whether stent retrievers were “predominantly” used. The analysis included 5 trials (Berkhemer et al., [16] Goyal et al., [17] Campbell et al., [18] Saver et al., [19] Jovin et al. [20]) with a total of 1287 patients. In pooled analysis for the review’s primary outcome, mRS scores at 90 days, patients randomized to endovascular therapy had an OR for more favorable mRS score of 2.2 (95% CI, 1.66 to 2.98; p<0.001; I2=46.38%). Similar to the findings from the Badhiwala meta-analysis, there were no significant between-group differences in 90-day mortality rates or symptomatic intracranial hemorrhage rates.

Similarly, Grech et al. conducted a systematic review and meta-analysis of RCTs comparing stent retriever devices (trials in which second-generation thrombectomy devices comprised at least 80% of thrombectomy devices used) with IV thrombolysis in acute stroke. (25) The systematic review included the same 5 trials as the Bush review (Berkhemer et al., [16] Goyal et al., [17] Campbell et al., [18] Saver et al., [19] Jovin et al. [20]). In pooled analysis, the OR for functional independence at 90 days between thrombectomy and IV thrombolysis groups was 2.4 (46.1% for thrombectomy versus 26.5% for IV thrombolysis; 90% CI for OR, 1.89 to 3.05; p<0.001).

The results of the Bush and Grech meta-analyses were supported by other systematic reviews of RCTs comparing stent retriever devices with standard care reported by Marmagkiolis et al. (2015) (26) and Touma et al. (2016). (27)

In 2015, an updated draft Blue Cross and Blue Shield Association (BCBSA) Technology Evaluation Center (TEC) Assessment assessed endovascular therapy for acute ischemic stroke in adults to reflect several RCTs published after an earlier BCBSA TEC Assessment. (28) The draft Assessment focused on 4 RCTs published from 2014 to 2015 comparing endovascular mechanical embolectomy with medical therapy (Berkhemer et al., [16] Goyal et al., [17] Campbell et al., [18] Saver et al. [19]). The Assessment made the following observations and conclusions:

“Four recent well-designed and well-conducted RCTs have demonstrated reduced disability among adults with acute ischemic stroke treated with mechanical embolectomy compared with standard medical care, usually IV-tPA. These 4 RCTs address some of the limitations in 3 RCTs published in 2013, which showed no significant benefit to endovascular therapy. In particular, trials demonstrating a benefit to endovascular therapy either exclusively used stent retriever devices or allowed the treating physician to select a device, mostly a stent retriever device, and had high rates of mechanical embolectomy device use in patients randomized to endovascular therapy.”

The draft Assessment concluded that the use of endovascular treatment with mechanical embolectomy in adults with radiologically confirmed large vessel, anterior circulation acute ischemic stroke met the BCBSA TEC criteria. The specific RCTs are described in more detail below.

The 2014 TEC Assessment, (28) which included 3 RCTs comparing endovascular treatment with standard stroke care (Ciccone et al., [13] Kidwell et al. [14], Broderick et al. [15]) and 2 RCTs comparing newer and older endovascular treatments (Saver et al., [29] Nogueira et al. [30]), concluded that endovascular therapy for acute stroke did not meet the BCBSA TEC criteria.

In 2015, Prabhakaran et al. published results from a systematic review of studies evaluating thrombolysis and mechanical thrombectomy in acute stroke. (31) The authors included 68 articles (total N=108,082 patients), including RCTs, observational studies, guideline statements, and review articles. Six RCTs comparing endovascular therapy with standard management were included. Although pooled trial results were not presented, the authors reported that, across the available RCTs, rates of substantial reperfusion (Thrombolysis In Cerebral Infarction [TICI] score 2b or 3) were positively associated with the proportion of patients with a good clinical outcome (mRS score, 0-2) at 90 days, while time to reperfusion was negatively associated with the proportion of patients with a good clinical outcome at 90 days.

Zheng and Xie conducted a meta-analysis of RCTs comparing endovascular therapy with IV-tPA, with analysis stratified by whether computed tomography angiography (CTA) was used to select patients for endovascular therapy. (32) The review included 7 RCTs with 2217 patients (Ciccone et al., [13] Kidwell et al., [14] Broderick et al., [15] Berkhemer et al., [16] Goyal et al., [17] Campbell et al. [18]), of which 4 used CTA to select patients. Endovascular therapy was associated with functional independence at 90 days in patients who underwent CTA-based selection (RR=1.75; 95% CI, 1.48 to 2.06; I2=0.05%), but not in patients who did not undergo CTA-based selection (RR=0.99; 05% CI, 0.85 to 1.14; I2=0.0%). All-cause mortality was not significantly associated with 90-day mortality, regardless of whether patients were selected with CTA.

Earlier published systematic reviews and meta-analyses have incorporated some RCTs comparing endovascular therapies and standard therapy, or were published before RCTs were available. (20, 33-38) The results are less relevant given the availability of more recent RCT data.

A group of investigators have formed the VISTA-TREAT collaboration to develop protocols for patient-level meta-analyses of pooled data from RCTs in which at least 85% of treated cases have received newer devices (direct aspiration catheters or stent retrievers). (39)

Randomized Controlled Trials (RCTs)

RCTs Comparing Endovascular Therapies with Noninterventional Care

From 2012 to 2015, results from 8 large RCTs comparing endovascular therapies with standard of care for acute ischemic stroke were published. Five prospective, open-label, blinded end point (PROBE design) RCTs comparing endovascular therapy with standard care in the treatment of acute stroke were published from 2014 to 2015 and are the focus of this discussion. A high-level overview of the major RCTs follows, with a summary of results in Table 2. Subsequently in this section, the trials are described in more detail.

Although the RCTs report on a number of outcomes, results pertaining to 3 specific outcomes are the focus here: the proportion of patients with 90-day mRS score between 0 and 2, short-term mortality rate, and rates of symptomatic intracranial hemorrhage. The primary goal of rapid revascularization in acute stroke is to reduce rates of significant disability; mRS scores ranging from 0 to 2 correspond to functional independence, and so represent a clinically useful measure of disability. Prior studies of endovascular therapy and thrombolytic therapy for acute stroke have been associated with increased risks of symptomatic intracranial hemorrhage, so this is another important safety-related outcome to evaluate.

Eight RCTs with a total of 2423 patients (range, 70-656 patients) compared endovascular mechanical embolectomy with standard care for acute ischemic stroke. In 2 studies, the population and intervention delivered were not consistent with the target population and intervention; the remaining 6 studies with the populations and interventions of interest are the focus of this discussion. The most clinically relevant and consistently reported finding was a comparison between treatment and control groups in the proportion of patients with a mRS score between 0 and 2 at 90 days. Among the 6 studies reporting on the populations and interventions of interest, all provide some information on the proportion of patients with 90-day mRS scores of 0-2. Across the studies, the absolute difference between treatment and control groups in proportion of patients with 90-day functional independence ranged from 1.55% to 25%. With 1 exception (MR Rescue [Kidwell et al. {14}]), all studies reported a statistically significant improvement in the proportion of patients with functional independence at 90 days, with ORs ranging from 1.7 to 3.8. Among the 6 studies reporting on the populations and interventions of interest, mortality rates and symptomatic intracranial hemorrhage rates did not differ significantly between study groups. It is not possible to draw conclusions about the safety or harm of the procedure from this finding; the lack of significant difference may be due to inadequate sample sizes.

REVASCAT Trial. In 2015, Jovin et al. reported results of the REVASCAT trial, which compared endovascular therapy using the Solitaire™ stent retriever device with medical therapy, including IV-tPA when indicated, within 8 hours of stroke onset among 206 patients. (20) Eligible patients had an occlusion within the proximal anterior circulation that could be treated within 8 hours of stroke onset, a prestroke mRS score of 0 to 1, and a baseline National Institutes of Health Stroke Scale (NIHSS) score of at least 6 points (NIHSS score range, 0-42; higher scores associated with greater deficit). IV-tPA was administered before randomization. Patients were excluded if they had imaging-based evidence of a large ischemic core, indicated by an Alberta Stroke Program Early Computed Tomography Score (ASPECTS) of less than 7 on non?contrast computed tomography (CT) imaging or a score of less than 6 on diffusion-weighted magnetic resonance imaging (MRI). The trial was halted early for loss of clinical equipoise (the ethical basis for medical research that involves assigning patients to different treatment arms of a clinical trial) given the results of the EXTEND-IA, ESCAPE, and MR CLEAN trials (described below in Tables 2 through 9 in addition to other clinical trial results) after the first planned interim analysis (when the first 25% of patients [n=174] reached 90 days of follow-up).

One hundred three patients were randomized to mechanical embolectomy, of whom 98 successfully underwent thrombectomy. Rates of tPA use between the groups did not differ significantly (68.0% in the mechanical embolectomy group, 77.7% in the control group). For the study’s primary outcome, the OR for improvement in the distribution of the mRS score was 1.7 (95% CI, 1.05 to 2.8), favoring mechanical embolectomy. A greater proportion of patients in the mechanical embolectomy group was functionally independent (mRS score, 0-2; 43.7% versus 28.2% in the control group; absolute risk difference, 15.5%; adjusted OR=2.1; 95% CI, 1.1 to 4.0). There were no significant differences between the mechanical embolectomy and the control groups in 90-day mortality (18.4% versus 15.5%; p=0.60) or 90-day rates of symptomatic intracranial hemorrhage (1.9% in each group; p=1.00).

Table 2: Summary of Each RCT of Endovascular Therapy Versus Standard Care – REVASCAT Trial (Jovin, 2015) (20)

Variables

Groups

Intervention

Control

Treatment Description

Solitaire™ stent retriever w/wo IV-tPA

Medical therapy (IV-tPA if indicated)

Number

103

103

90-Day Modified Rankin Scale Score 0-2

Per Group Rate

43.7%

28.2%

Between-Group Difference

ARR=15.5%; OR=2.1 (95% CI, 1.1 to 4.0)

 

Mortality

Per Group Rate

18.4%

15.5%

Between-Group Difference

p=0.60

 

Symptomatic Intracranial Hemorrhage

Per Group Rate

1.9%

1.9%

Between-Group Difference

p=NS

 

Table Key for the following Tables 2 through 9:

ARR: absolute risk reduction;

CI: confidence interval;

IV: intravenous;

OR: odds ratio;

RCT: randomized controlled trial;

RR: risk ratio;

tPA: tissue plasminogen activator;

w/wo: with/without;

p: p-value;

NS: not significant.

EXTEND-IA Trial. In 2015, Campbell et al. reported results of the EXTEND-IA trial comparing endovascular therapy with tPA alone. (18) This trial enrolled patients with ischemic stroke who were receiving IV-tPA within 4.5 hours after stroke onset. Eligible patients had an occlusion of the internal carotid artery (ICA) or M1 or M2 segments of the middle cerebral artery (MCA) on CTA, were able to receive endovascular therapy within 6 hours of stroke onset, and were functionally independent prior to the stroke. Patients were evaluated prior to enrollment with CT perfusion imaging, and were required to have evidence of salvageable brain tissue and an ischemic core with a volume of less than 70 mL. CT perfusion imaging was analyzed with an operator-independent postprocessing software. Enrollment was planned for 100 patients. The trial’s data safety and monitoring board reviewed data for the first 70 enrolled patients after the results of the MR CLEAN trial were published and stopped EXTEND-IA for efficacy based on prespecified criteria. The first 70 patients were randomized to either IV-tPA plus endovascular therapy with the Solitaire™ FR retrievable stent (n=35) or no further therapy (IV-tPA only; n=35). The study used 2 coprimary end points: reperfusion (measured as the percentage reduction in perfusion-lesion volume between the initial imaging and imaging at 24 hours) and early neurologic improvement (defined as a reduction of ≥8 points on the NIHSS or a score of 0 or 1 at day 3).

The demographics of the randomized groups were similar at baseline. About 25% of clinically eligible patients were excluded on the basis of perfusion imaging criteria. In the endovascular group, 8 (22.9%) of 35 patients did not undergo mechanical embolectomy, most commonly because most of the thrombus was lysed before angiography (n=4). Endovascular therapy subjects had increased reperfusion at 24 hours, with a median reperfusion of 100% (percentage reduction in perfusion-lesion volume), compared with 37% for the tPA-only group (adjusted OR=4.7; 95% CI, 2.5 to 9.0; p<0.001). Of the endovascular therapy subjects, 28 (80%) of 35 had early neurologic improvement compared with 13 (37%) of 35 of the tPA-only subjects (adjusted OR=6.0; 95% CI, 2.0 to 18.0; p=0.002). Rates of reperfusion of at least 90% at 24 hours without symptomatic intracerebral hemorrhage were higher in endovascular therapy patients (89% versus 34%; adjusted OR=27.0; 95% CI, 5.5 to 135.0; p<0.001). Safety outcomes, including death, symptomatic intracerebral hemorrhage, and parenchymal hematoma, did not differ significantly between groups.

Table 3: Summary of Each RCT of Endovascular Therapy Versus Standard Care – EXTEND-IA Trial (Campbell, 2015) (18)

Variables

Groups

Intervention

Control

Treatment Description

Endovascular therapy + IV-tPA

IV-tPA alone

Number

35

35

90-Day Modified Rankin Scale Score 0-2

Per Group Rate

71%

40%

Between-Group Difference

OR=3.8 (95% CI, 1.4 to 1.0)

 

Mortality

Per Group Rate

20%

9%

Between-Group Difference

OR=0.38 (95% CI, 0.1 to 1.6)

 

Symptomatic Intracranial Hemorrhage

Per Group Rate

6%

0%

Between-Group Difference

Risk difference, -6 (95% CI, -13 to 2)

 

Refer to Table Key Following Table 2 for Definitions of Acronyms in the Table Just Above.

ESCAPE Trial. Also in 2015, Goyal et al. reported results of the ESCAPE trial that compared endovascular therapy with guideline-based stroke care, including IV-tPA if indicated. (17) Patients with acute stroke were eligible if they presented within 12 hours of stroke onset, had a proximal intracranial occlusion in the anterior circulation, and had non-contrast CT or CTA with the following findings: 1) small infarct core; 2) proximal artery occlusion, defined by occlusion of the MCA trunk and its immediate branches, with or without intracranial occlusion of the ICA; and 3) moderate-to-good collateral circulation, defined as filling of 50% or more of the MCA pial artery circulation on CTA. A small infarct core was defined as a score of 6 to 10 on the ASPECTS, which is a 10-point scoring system designed to quantify the extent of ischemic changes in the MCA territory. Patients received IV-tPA if they met local guidelines. Patients were randomized to endovascular treatment (n=165), which could include any U.S. Food and Drug Administration (FDA)-approved stent retriever or aspiration device, balloon angioplasty, guidewire manipulation, and/or intra-arterial tPA, or guideline-based stroke care (n=150). Use of retrievable stents was recommended. Enrollment was planned for 316 subjects. The trial was stopped early on the advice of its data safety monitoring board, after an unplanned interim analysis following publication of MR CLEAN trial results, because ESCAPE’s prespecified efficacy boundary had been crossed.

Of the 165 patients randomized to the intervention group, 151 (91.5%) underwent endovascular therapy, most commonly with a retrievable stent (130/151 [86.1%] of those who underwent an endovascular procedure), most often with the Solitaire™ stent (100/130 [77.0%] of those who received a retrievable stent). In the intervention group, 120 (72.7%) also received IV-tPA. Of the 150 control group subjects, 118 (78.6%) received IV-tPA. For the study’s primary end point (90-day mRS score), compared with the control group, in the endovascular treatment group the relative odds of improving 1 point on the mRS was 2.6 (95% CI, 1.7 to 3.8). Endovascular treatment group subjects compared with control group subjects also had lower 90-day mRS scores (median, 2 versus 4, respectively; p<0.001) and were more likely to have 90-day mRS scores of 0 to 2 (53% versus 29.3%; rate ratio, 1.8; 95% CI, 1.4 to 2.4; p<0.001). Ninety-day mortality was 10.4% among endovascular treatment group subjects and 19.0% in control group subjects (rate ratio, 0.5; 95% CI, 0.3 to 1.0; p=0.04).

Table 4: Summary of Each RCT of Endovascular Therapy Versus Standard Care – ESCAPE (Goyal, 2015) (17)

Variables

Groups

Intervention

Control

Treatment Description

Endovascular therapy w/wo IV-tPA

Medical therapy (IV-tPA if indicated)

Number

165

150

90-Day Modified Rankin Scale Score 0-2

Per Group Rate

53%

29.3%

Between-Group Difference

RR=1.8 (95% CI, 1.4 to 2.4)

 

Mortality

Per Group Rate

10.4%

29.05%

Between-Group Difference

RR=0.5 (95% CI, 0.3 to 1.00)

 

Symptomatic Intracranial Hemorrhage

Per Group Rate

   

Between-Group Difference

   

Refer to Table Key Following Table 2 for Definitions of Acronyms in the Table Just Above.

SWIFT-PRIME Trial. In 2015, Saver et al. reported results of the SWIFT-PRIME trial comparing IV-tPA followed by mechanical embolectomy using a stent retriever device with IV-tPA alone in patients presenting with acute ischemic stroke. (40) Eligible patients had moderate-to-severe neurologic deficits, imaging-confirmed occlusion of the intracranial ICA and/or the first segment of the MCA, were receiving or had received IV-tPA, and were able to undergo endovascular treatment within 6 hours of symptom onset. In addition, eligible patients were required to have ischemic penumbral imaging analysis showing a small-to-moderate core infarct. For the first 71 patients enrolled, the infarct core size was defined based on CT perfusion imaging analyzed with an operator-independent postprocessing software; for the remainder of the study, infarct core size could be determined by CT perfusion imaging or non-contrast CT with a small-to-moderate core infarct based on ASPECTS. Patients were randomized to mechanical embolectomy with the Solitaire™ 2 or the Solitaire™ FR device (n=98) or to ongoing IV-tPA (n=98). Enrollment was planned for a maximum of 833 subjects, but stopped at 196 subjects after an interim analysis, following publication of the results of the MR CLEAN and ESCAPE trials, showed that results met SWIFT-PRIME’s prespecified efficacy criteria.

In the intervention group, a stent retriever was successfully deployed in 87 (89%) patients. At 90 days, 60% of endovascular therapy group patients were functionally independent (mRS score, 0-2) compared with 35% of control subjects (absolute risk reduction, 25%; OR=1.70; 95% CI, 1.23 to 2.33; p<0.001). Endovascular therapy group patients compared with controls were more likely to have successful (≥90%) reperfusion at 27 hours (83% versus 40%, respectively; OR=2.05; 95% CI, 1.45 to 2.91; p<0.001). Rates of death and serious adverse events did not differ significantly between groups.

Table 5: Summary of Each RCT of Endovascular Therapy Versus Standard Care – SWIFT-PRIME (Saver, 2015) (40)

Variables

Groups

Intervention

Control

Treatment Description

Solitaire™ stent retriever + IV-tPA

IV-tPA alone

Number

98

98

90-Day Modified Rankin Scale Score 0-2

Per Group Rate

60%

35%

Between-Group Difference

ARR=25%; OR=1.70 (95% CI, 1.23 to 2.33)

 

Mortality

Per Group Rate

9%

12%

Between-Group Difference

RR=0.74 (95% CI, 0.33 to 1.68)

 

Symptomatic Intracranial Hemorrhage

Per Group Rate

0%

3%

Between-Group Difference

p=0.12

 

Refer to Table Key Following Table 2 for Definitions of Acronyms in the Table Just Above.

MR CLEAN Trial. In 2015, Berkhemer et al. reported initial results of the MR CLEAN trial, an open-label, blinded end point RCT with 500 subjects conducted at 16 centers in the Netherlands. (16) Eligible patients had acute ischemic stroke caused by an intracranial occlusion of the distal intracranial carotid artery, MCA (M1 or M2), or anterior cerebral artery (A1 or A2), and a score of 2 or higher on the NIHSS. Initiation of intra-arterial treatment had to be possible within 6 hours of stroke onset. Patients were randomly assigned to standard stroke treatment (n=267 [53.4%]) or intra-arterial treatment (n=233 [46.6%]). Most patients in both groups (87.1% in the intervention group, 90.6% in the control group) received IV alteplase, at a median of 85 and 87 minutes after stroke onset, respectively. Patients in the intra-arterial group underwent arterial catheterization with a microcatheter to the level of the occlusion. Specific treatment options included delivery of a thrombolytic agent, mechanical thrombectomy, or both, at the discretion of the local interventionist. Intra-arterial thrombolytic agents were either alteplase or urokinase; mechanical treatment could involve thrombus retraction, aspiration, wire disruption, or use of a retrievable stent. Analysis was intention-to-treat. One control group patient received intra-arterial treatment, and 17 (7.3%) patients in the intervention group did not receive intra-arterial therapy, most commonly (n=8) due to clinical improvement before the start of the intervention. Among the 233 patients randomized to intra-arterial therapy, 195 (83.7%) received mechanical therapies, with retrievable stents used in 190 (81.5%) patients and other devices in 5 (2.1%) patients. Twenty-four (10.3%) patients received additional intra-arterial thrombolytic agents. No intra-arterial intervention was performed following catheterization in 20 subjects because of intracranial artery stenosis, occlusion, tortuosity, or dissection (n=10), no clot or targetable clot visible for intra-arterial therapy (n=8), or other technical problems (n=2).

For the study’s primary outcome (mRS score at 90 days), the median score was 3 (interquartile range [IQR], 2-5) among intervention subjects, compared with a median score of 4 (IQR, 3-5) among control subjects, with an unadjusted common OR of 1.66 (95% CI, 1.21 to 2.28; favors intervention). Twenty-seven (11.6%) intervention subjects had an mRS score of 0 or 1 at 90 days, compared with 16 (6.0%) control subjects (unadjusted OR=2.06; 95% CI, 1.08 to 3.92). Follow-up CTA was available for 187 control subjects, of whom 141 (75.4%) had no intracranial occlusion, compared with 68 (32.9%) of 207 control subjects with follow-up CTA available (unadjusted OR=6.27; 95% CI, 4.03 to 9.74). The 30-day mortality rate was 18.9% in the intervention group and 18.4% in the control group (p=NS). Rates of serious adverse events (AEs) during the 90-day follow-up did not differ significantly between groups (p=0.31). Symptomatic intracerebral hemorrhage occurred in 7.7% of intervention subjects and 6.4% of control subjects, which was not a significant difference. However, intervention subjects were more likely to demonstrate a new ischemic stroke in different vascular territory (5.6% versus 0.4%; p<0.001).

Table 6: Summary of Each RCT of Endovascular Therapy Versus Standard Care – MR CLEAN (Berkhemer, 2015) (16)

Variables

Groups

Intervention

Control

Treatment Description

Intra-arterial therapy w/wo IV-tPA

Medical therapy (IV-tPA if indicated)

Number

233

267

90-Day Modified Rankin Scale Score 0-2

Per Group Rate

32.6%

19.1%

Between-Group Difference

ARR=13.5%; OR=2.05 (95% CI, 1.36 to 3.09)

 

Mortality

Per Group Rate

18.9%

18.4%

Between-Group Difference

p=NS

 

Symptomatic Intracranial Hemorrhage

Per Group Rate

7.7%

6.4%

Between-Group Difference

p=NS

 

Refer to Table Key Following Table 2 for Definitions of Acronyms in the Table Just Above.

MR RESCUE Trial. Kidwell et al. reported on the MR RESCUE trial in 2013. (14) MR RESCUE was an open-label, blinded-outcome RCT of 118 patients from 22 North American sites. All patients had large vessel, anterior circulation ischemic strokes and were stratified by penumbral pattern, as determined by pretreatment CT or MRI of the brain. Patients were randomly assigned to standard stroke treatment (n=54) or mechanical embolectomy (n=64) using the Merci® Retriever or Penumbra System® within 8 hours after presentation of symptoms. Eight patients in the embolectomy group also had tPA. The primary hypothesis of the study was that patients with favorable penumbral patterns (at-risk area of viable ischemic cerebral tissue of >70% and a small, >90 mL, area of predicted core infarct) would benefit more from mechanical embolectomy than patients with non?penumbral patterns (large infarct area and small or absent penumbra [viable ischemic cerebral tissue]), as determined by the 90-day mRS score. In the embolectomy group, 67% achieved revascularization, but this was not superior to standard care. Mean mRS scores were the same (3.9) in both groups, and pretreatment imaging patterns did not show any relation to treatment outcomes in any group. Overall mortality (21% at 90 days) and symptomatic intracranial hemorrhage (4%) did not differ across groups.

Table 7: Summary of Each RCT of Endovascular Therapy Versus Standard Care – MR RESCUE (Kidwell, 2013) (14)

Variables

Groups

Intervention

Control

Treatment Description

Mechanical embolectomy (Merci® or Penumbra®) w/wo IV-tPA

Medical therapy (IV-tPA if indicated)

Number

64

54

90-Day Modified Rankin Scale Score 0-2

Per Group Rate

18.75%

20.3%

Between-Group Difference

p=0.48

 

Mortality

Per Group Rate

21%

21%

Between-Group Difference

p=NS

 

Symptomatic Intracranial Hemorrhage

Per Group Rate

4%

4%

Between-Group Difference

p=NS

 

Refer to Table Key Following Table 2 for Definitions of Acronyms in the Table Just Above.

SYNTHESIS Expansion Trial. In 2013, Ciccone et al. reported on the SYNTHESIS Expansion trial of 362 patients randomized within 4.5 hours of the onset of various types of acute ischemic strokes to receive endovascular therapy (n=181) or IV-tPA (n=181). (13) Endovascular therapy consisted of intra-arterial tPA, mechanical embolectomy (using the Solitaire™, Penumbra®, Trevo®, Merci® devices), or a combination of these treatments. Among the patients randomized to endovascular therapy, endovascular treatment was completed in 163 patients. In 109 patients, regional intra-arterial infusion of tPA and fragmentation of the thrombus with a microguidewire were used. In 56 patients, a device was added; the most widely used devices were Solitaire™ FR in 18 patients, Penumbra® in 9 patients, Trevo® in 5 patients, and Merci® in 5 patients. No significant differences in 90-day survival without disability (mRS score range, 0-1) occurred between the endovascular therapy (30.4%) group and tPA group (34.8%; adjusted OR=0.71; 95% CI, 0.44 to 1.14; p=0.16). Within 7 days, fatal or nonfatal symptomatic intracranial hemorrhage occurred in each group at a rate of 6%. Rates of other serious AEs also did not differ significantly between groups. While there were different treatment approaches in the endovascular group, these results suggest endovascular therapy is not superior to tPA.

Table 8: Summary of Each RCT of Endovascular Therapy Versus Standard Care – SYNTHESIS Expansion (Ciccone, 2013) (13)

Variables

Groups

Intervention

Control

Treatment Description

Intra-arterial therapy w/wo IV-tPA

IV-tPA alone

Number

181

181

90-Day Modified Rankin Scale Score 0-2

Per Group Rate

30.4%

34.8%

Between-Group Difference

OR=0.71 (95% CI, 0.44 to 1.14)

 

Mortality

Per Group Rate

   

Between-Group Difference

   

Symptomatic Intracranial Hemorrhage

Per Group Rate

6%

6&

Between-Group Difference

p=NS

 

Refer to Table Key Following Table 2 for Definitions of Acronyms in the Table Just Above.

IMS III Trial. Also in 2013, Broderick et al. reported the results of the IMS III trial, an open-label RCT with a planned enrollment of 900 patients. (15) This trial enrolled patients with acute ischemic stroke who presented within 3 hours of symptom onset and had a moderate-to-severe neurologic deficit on presentation. Patients were randomized to IV-tPA alone or IV-tPA plus endovascular intervention. Patients randomized to the endovascular group underwent immediate angiography followed by endovascular intervention if a treatable vascular occlusion was present. Endovascular intervention consisted of either endovascular delivery of tPA at the site of occlusion or mechanical thrombectomy, at the discretion of the treating physician. Potential endovascular interventions included thrombectomy (using the Merci® Retriever, Penumbra System®, or Solitaire™ FR revascularization device) or endovascular delivery of tPA (using the Micro-Sonic SV infusion system [EKOS] or a standard microcatheter). The primary outcome was an mRS score of 2 or less at 90 days. The trial was stopped prematurely due to futility after enrollment of 656 patients. At that point, the primary outcome had been reached by 40.8% of patients in the endovascular group and 38.7% of patients in the IV-tPA group. The adjusted difference in the primary outcome was 1.5%, with a 95% CI for the difference of -6.1 to 9.1. Subarachnoid hemorrhage was more frequent in the endovascular group than in the tPA group (11.5% versus 5.8%, respectively; p=0.02), as was asymptomatic intracerebral hemorrhage (27.4% versus 18.9%, p=0.01). There were no significant differences between groups in other AEs, including death and symptomatic intracerebral hemorrhage. In a predefined subgroup analysis, the authors reported that for the subgroup of patients with ICA, M1, or basilar artery occlusion who received tPA within 120 minutes of stroke onset (n=124), the relative risk (RR) for an mRS score of 2 or less at 90 days was not statistically significant (RR=1.18; 95% CI, 0.66 to 2.1).

In 2015, Tomsick et al. published a subgroup analysis of the IMS III trial focusing on subjects with intracranial ICA or M1 occlusion. (41) This analysis included 200 subjects, 65 with intracranial ICA and 135 with M1 segments as the target vessel for revascularization. Of these, at angiography, 82% had an arterial occlusive lesion score of 2 to 3 and 76% had a modified thrombolysis in cerebral infarction (mTICI) scores of 2 or 3 (partial or full perfusion) after IV-tPA, which may have limited the potential benefit for device-related revascularization. Ninety-day mRS scores were higher with higher mTICI scores: of 32 subjects with an mTICI score of 0, 3.1% had an mRS score of 0 to 2 at 90 days, compared with 12.5%, 19.4%, 46.3%, and 80% for subjects with mTICI scores of 1 (n=16), 2a (n=67), 2b (n=80), and 3 (n=5), respectively. To account for potential bias in the choice of endovascular therapy, propensity score analysis was used to compare subjects with different endovascular therapy modalities for the primary study outcomes. After propensity score adjustment, the authors found no clear differences in clinical or revascularization outcomes across revascularization methods, which included standard microcatheter thrombolysis (n=51), the EKOS catheter (n=14), the Merci® retriever (n=77), the Penumbra® device (n=39), the Solitaire™ device (n=4), and other methods (n=15).

In another IMS III subgroup analysis, Demchuk et al. evaluated the association between baseline CT or magnetic resonance angiography (MRA) findings and outcomes among 306 (47%) of 656 who had baseline CT or MRA imaging available. (42) Ninety-two percent of those with angiography available had arterial occlusions demonstrated, 220 of which were proximal occlusions. Endovascular therapy group subjects with proximal occlusions had higher 24-hour recanalization rates than those with IV-tPA only (84.3% of endovascular therapy subjects versus 56% of controls; p<0.001). However, no difference in the primary outcome (90-day mRS score, 0-2), was seen with proximal occlusions between groups (41.3% of endovascular therapy subjects versus 38% of controls; RR=1.07; 99% CI, 0.67 to 1.70).

Table 9: Summary of Each RCT of Endovascular Therapy Versus Standard Care – IMS III (Broderick, 2013) (15)

Variables

Groups

Intervention

Control

Treatment Description

Endovascular therapy + IV-tPA

IV-tPA alone

Number

434

222

90-Day Modified Rankin Scale Score 0-2

Per Group Rate

38.7%

40.8%

Between-Group Difference

Adjusted difference: 1.5% (95% CI, -6.1 to 9.1)

 

Mortality

Per Group Rate

19.1%

21.6%

Between-Group Difference

p=0.52

 

Symptomatic Intracranial Hemorrhage

Per Group Rate

11.5%

18.9%

Between-Group Difference

p=0.02

 

Refer to Table Key Following Table 2 for Definitions of Acronyms in the Table Just Above.

Section Summary: RCTs Comparing Endovascular Therapies with Noninterventional Care

A number of RCTs have compared endovascular therapies with noninterventional care for acute stroke, with the 5 more recent (2014-2015) studies demonstrating a significant benefit associated with endovascular care. The more recently published trials addressed some of the limitations of previous studies. In the IMS III and SYNTHESIS Expansion trials, sizable proportions of the endovascular therapy groups did not receive an endovascular device. All 3 of the 2013 trials (Ciccone et al., [13] Kidwell et al., [14] Broderick et al. [15]) had relatively low utilization of the newer generation retrievable stents (Solitaire™ FR, Trevo®). In addition, IMS III and SYNTHESIS Expansion did not require a radiologically proven intracranial occlusion for study eligibility. In contrast, the 2014-2015 trials, which demonstrated a benefit to endovascular therapy, either exclusively used stent retriever devices or allowed the treating physician to select a device, mostly a stent retriever device, and had high rates of mechanical embolectomy device use in patients randomized to endovascular therapy.

RCTs Comparing Different Endovascular Therapies

In 2012, 2 noninferiority RCTs comparing newer devices with the Merci® Retriever were completed as part of the FDA application for approval of the Solitaire™ and the Trevo® devices. Both studies reported device superiority over the Merci® device. In the SWIFT study, recanalization rates with Solitaire™ were compared with the Merci® Retrieval System in a randomized, prospective noninferiority trial of 113 patients with moderate or severe large vessel occlusion strokes. (29) Treatment was initiated within 8 hours of symptom onset in patients who had unsuccessful IV-tPA or were ineligible for IV-tPA. This trial was halted early after an interim analysis found revascularization without symptomatic intracranial hemorrhage occurred in 61% of Solitaire™ patients compared with 24% of Merci® patients. Mortality rates at 90 days were 17% with Solitaire™ versus 38% with Merci® (p=0.001). A follow-up analysis of complications of endovascular procedures using the SWIFT study data was published in 2014. (43) This analysis included 144 patients with acute ischemic stroke (31 patients treated with the Solitaire™ FR device during the SWIFT trial roll-in period, 113 patients randomly assigned to the Solitaire™ FR or Merci® device). Major periprocedural complications, including symptomatic intracranial hemorrhage, air emboli, vessel dissection, major groin complications, and emboli to new vascular territories, were seen in 18 (12.5%) of 144 of patients. Complication rates were similar for patients receiving the Solitaire™ FR and Merci® devices, with the exception of symptomatic cerebral hemorrhage, which was significantly less common in the Solitaire™ FR group (10.9% versus 1.1%, p=0.013).

In the TREVO 2 Study, 178 patients were randomized to receive mechanical embolectomy with either the Trevo® Retriever or the Merci® Retriever for large vessel occlusion strokes. (30) Revascularization rates were 86% in the Trevo® group and 60% in the Merci® group (p<0.001). Procedure-related AEs occurred in 15% of the Trevo® group and 23% in the Merci® group (p=0.183). Mortality rates at 90 days were 33% and 24% (p=0.18), respectively.

In 2015, Saposnik et al. (44) evaluated the benefit added by stent retrievers to IV-tPA using pooled patient-level data from the SWIFT study (29) and the STAR trial, a prospective, single-arm trial of the Solitaire™ device, (45) along with data from the NINDS tPA Stroke Study, an RCT evaluating IV-tPA. Of 915 patients included in the pooled analysis, 312 were treated with placebo, 312 with IV-tPA, 106 with stent retrievers alone, and 160 with IV-tPA and stent retrievers. The authors used a shift analysis, which uses a proportional odds model, to evaluate the association between treatment and each of the 7 mRS categories. The use of stent retrievers (alone or with tPA) was associated with a higher probability of functional independence (mRS score, 0-2) at 90 days: 41% of those treated with tPA alone, 69.8% of those treated with stent retrievers, and 72.8% of those treated with stent retrievers and tPA had functional independence at 90 days.

Nonrandomized Comparative Studies

A number of nonrandomized comparative studies have compared endovascular interventions with historical controls or control patients from their same institution who received standard stroke care (e.g., Rai et al., [46] Urra et al., [47] Song et al., [48] Alexandrov et al., [49] Taschner et al. [50]).

For the treatment of acute stroke involving the anterior circulation, more direct evidence on the effectiveness of endovascular therapies, compared with standard treatment, is available from the RCTs described above. Therefore, nonrandomized comparative studies that have assessed specific types of endovascular interventions are the focus of this section. These studies offer information on the comparative efficacy of different devices, which is important in the interpretation and comparison of studies that may use different or multiple devices in endovascular treatments of acute stroke.

Kappelhof et al. conducted a systematic review and meta-analysis of studies comparing outcomes for mechanical therapy and intra-arterial thrombolysis for acute ischemic stroke due to ICA occlusion, with separate results reported for intracranial and extracranial occlusions. (51) The overall review included 32 studies, 6 of which (n=95 patients) reported outcomes for intracranial occlusion treated by intra-arterial thrombolysis and 8 of which (n=115 patients) reported outcomes for intracranial occlusion treated by mechanical thrombectomy. None of the recently published RCTs of endovascular therapy were included in the review (studies published through July 2013), which specifically reported outcomes for ICA occlusions. In the subset of studies reporting on intracranial occlusions, overall outcome rates were 55% recanalization, 12% symptomatic intracranial hemorrhage, 34% mortality, and 25% favorable outcome. Compared with intra-arterial fibrinolysis, mechanical thrombectomy was associated with a higher recanalization rate (69% versus 38%; p<0.001), a higher rate of favorable outcomes (34% versus 14%; p<0.001), with nonsignificantly different rates of death (29% versus 40%; p=0.085) and symptomatic intracranial hemorrhage (12.2% versus 11.7%; p=0.085).

Turk et al. conducted a retrospective, single-center review comparing clinical and cost-related outcomes for 3 endovascular interventions for acute stroke: the Penumbra® system, stent retriever with local aspiration, and a “Direct Aspiration First Pass Technique” (ADAPT), which involves direct aspiration with a large bore catheter. (52) Two hundred twenty-two patients underwent endovascular therapies for acute stroke during the study, 128 (58%) with the Penumbra system®, 30 (13%) with a stent retriever, and 64 (29%) with ADAPT. Recanalization rates (TICI scores, 2b/3) were higher in the ADAPT group than in the Penumbra® group (95% versus 73%; p=0.003), but no significant differences were seen across groups in 90-day mRS scores.

Kass-Hout et al. compared retrievable stenting with the Merci® and Penumbra® devices in a retrospective analysis of 287 patients who underwent mechanical embolectomy at a single center. (53) In binary logistic regression, receiving a retrievable stent was an independent predictor of a good functional outcome (adjusted OR=2.27; 95% CI, 1.02 to 5.05; p=0.045). Broussalis et al. compared the Merci® device with newer retrievable stents (Trevo® and Solitaire™ devices) in 122 patients treated with endovascular interventions and reported that recanalization rates were higher with the newer devices (82% versus 62%, p=0.016). (54) Mendonca et al. compared the Trevo® and Solitaire™ devices in a prospective, nonrandomized comparison of 33 patients with anterior cerebral circulation occlusions. (55) No significant differences between devices were found in rates of revascularization, symptomatic intracranial hemorrhage, improvements in mRS scores, or mortality. In a similar but smaller study, Fesl et al. compared 14 patients treated with a newer retrievable stent with 16 patients treated with an older device. (56) Recanalization rates were higher in the retrievable stent group (93% versus 56%, p<0.05).

Noncomparative Studies

Many single-arm studies have reported results from endovascular interventions for acute stroke. Many of the studies predated the IMS III, SYNTHESIS Expansion, MR RESCUE, and MR CLEAN RCTs outlined earlier. Representative studies include Flint et al., which reported outcomes from 80 patients treated with the Merci® device for occlusion of the intracranial ICA (57); and Lin et al., which reported outcomes from 75 patients with ICA terminus occlusions who received endovascular interventions with either intra-arterial thrombolytics or mechanical embolectomy with the Merci® device. (58) Multiple small, single-center case series (59, 60) and other smaller case series, which often included only intermediate outcomes such as vessel recanalization (61-64) evaluating endovascular treatments for acute stroke, also exist in the literature.

Multiple noncomparative retrospective and prospective studies reporting outcomes from endovascular therapies with the newer generation stent retriever devices, which are currently FDA-approved (e.g., Solitaire™ FR, Trevo®) and with non-FDA approved devices (e.g., Penumbra® Separator 3D) have been published. (45, 55, 65-79) While these studies do not directly provide evidence about the benefit of endovascular interventions compared with standard care for acute stroke, they do suggest significant variability in clinical outcomes at 3 months in patients treated with stent retriever devices, with rates of good clinical outcomes ranging from 39% to 77%.

Endovascular Interventions for Stroke Due to Basilar Artery Occlusion

Posterior circulation strokes account for about 20% of all acute ischemic strokes; occlusion of the basilar artery is implicated in about 8% of posterior strokes. (80) Reperfusion therapies have received particular attention as a therapy for basilar artery occlusion because, though relatively rare, those occlusions have high likelihood of severe disability or death. For example, in 1 registry study, investigators found severe outcomes (mRS scores of 4 or 5, or death) in 68% of patients with basilar artery occlusion. (81)

A limited number of studies have evaluated endovascular interventions for basilar artery occlusion. In 2013, Broussalis et al. reported results from a prospective registry study of 99 patients with posterior circulation stroke caused by basilar artery occlusion from 2005 to 2012. (82) Patients who received endovascular therapies (including endovascular mechanical recanalization and/or intra-arterial with optional IV thrombolytic therapy) were compared to those who received standard medical therapy (IV thrombolytic therapy and/or medical antithrombotic treatment.) Seventy-eight percent of the patients received endovascular intervention, with thrombectomy alone in 67 patients. Devices used included the Merci® system in 43%, the Solitaire™ FR device in 13%, and the Trevo® retriever in 18%, with devices not available in the U.S. in the remaining 25%. Endovascular patients were more likely to achieve a TICI score of 3 (full perfusion with filling of all distal branches) (36% versus 9%, p=0.017); after 90 days, more than 61% of patients who received endovascular therapy achieved an mRS score of 3 compared with 8% in the standard medical therapy group.

Noncomparative studies have reported on endovascular therapies for acute basilar artery occlusion. Son et al. reported outcomes for 31 subjects with acute basilar artery occlusion treated using mechanical thrombectomy with the Solitaire™ stent (n=13) or manual aspiration thrombectomy using the Penumbra® reperfusion catheter (n=18) at a single center. (83) Successful recanalization (TICI scores, ≥2b) did not differ between devices (84.6% with Solitaire™ versus 100% with Penumbra®; p=0.168); similarly, 3-month mRS scores did not differ between the groups (3.6 with Solitaire™ versus 3.2 with Penumbra®; p=0.726).

Huo et al. reported outcomes for 36 consecutive patients with acute basilar artery occlusion treated with the Solitaire™ stent. (84) Recanalization (TICI score ≥2b) was successful in 94.4% of patients. However, mortality at 90 days was high (30.56%). Of note, 30 (83.3%) patients had stenosis in the occluded artery and 25 patients (69.4% of all patients) also underwent angioplasty.

In a single-center case series of 24 patients with acute basilar artery occlusion treated with a stent retriever device with or without IV or intra-arterial tPA and/or percutaneous transluminal angioplasty or permanent stent placement, Mohlenbruch et al. reported that mechanical thrombectomy led to successful recanalization (TICI scores, ≥2b) in 18 (75%) of patients. (85) Eight (33%) patients had a favorable clinical outcome (mRS scores, 0-2) at 3 months. Park et al. reported results from a single-center case series of 16 patients with acute basilar artery occlusion treated with endovascular interventions, primarily the Penumbra® or Solitaire™ FR devices. (86) The authors reported that successful revascularization (TICI scores, ≥2a) was achieved in 81.3% of patients, with favorable clinical outcome (mRS scores, 0-2) at 3 months in 56.3% of patients. While these studies suggest that endovascular intervention is feasible for acute basilar artery occlusion and may be associated with favorable outcomes, they lack concurrent comparison groups and have potential selection bias.

Section Summary: Endovascular Interventions for Stroke due to Basilar Artery Occlusion

The evidence for the use of endovascular interventions for stroke due to basilar artery occlusions is limited, consisting on multiple noncomparative studies and 1 prospective registry study comparing endovascular therapy with standard medical therapy. These studies indicate that high rates of recanalization can be achieved with mechanical thrombectomy. However, additional comparative studies are needed to demonstrate that mechanical thrombectomy is superior to standard therapy.

Endovascular Interventions for Symptomatic Intracranial Atherosclerotic Disease

Two devices for treatment of intracranial stenosis received FDA approval through the humanitarian device exemption (HDE) process. The Neurolink System® was approved based on the SSYLVIA trial, a prospective, nonrandomized, multicenter, international study of 61 patients. (87) The Wingspan™ Stent System was evaluated in a prospective study of 45 patients enrolled at 12 international centers. (88) The SSYLVIA study reported an all-stroke rate of 13.1% over a mean follow-up of 216 days; the Wingspan™ study reported an all-stroke rate of 9.5% over a mean follow-up of 174 days.

The FDA summary of safety and effectiveness of the Wingspan™ device offered the following conclusions and appears to have based its approval in part on the favorable comparison to the Neurolink® device:

“…the probable benefit to health from using the Wingspan™ Stent System with Gateway PTA Balloon Catheter for treating transcranial stenosis outweighs the risk of illness or injury when used in accordance with the ‘Instructions for Use’ and when taking into account the probable risks and benefits of currently available alternative forms of treatment.” (89)

Evidence on the role of endovascular stenting for treatment of symptomatic intracranial atherosclerotic disease includes 2 RCTs, a number of nonrandomized comparative studies, and numerous single-arm series. The most clinically relevant RCTs, nonrandomized comparative studies, and systematic reviews are reviewed next. Since publication of the RCT evidence, there continue to be single-arm publications (i.e., with all subjects receiving endovascular stents) describing various aspects of stenting for intracranial stenosis, including utilization trends, (90) predictors of outcomes based on symptomatology, (91) predictors of outcomes based on lesion morphology and arterial access, (92) and clinical outcomes with the Wingspan™ system. (93)

Randomized Controlled Trials

In 2015, Zaidat et al. published results of the VISSIT trial, an RCT comparing a balloon-expandable stent plus medical management to medical management alone among patients with symptomatic intracranial stenosis of 70% or greater. (94) Eligible patients had stenosis of 70% to 99% of the internal carotid, middle cerebral, intracranial vertebral, or basilar arteries with a transient ischemic attack (TIA) or stroke attributable to the territory of the target lesion within the prior 30 days. Enrollment was planned for up to 250 participants. However, an early unplanned analysis was conducted by the trial sponsor after the results of the SAMMPRIS trial were published (see below). A total of 112 patients were enrolled from 2009 to 2012 and randomized to balloon-expandable stent (Vitesse™ stent) plus medical management (stent group; n=59) or medical management alone (medical group; n=53). Medical management included clopidogrel (75 mg daily) for the first 3 months’ post-enrollment and aspirin (81-325 mg/d) for the duration of the study, along with management of hypercholesterolemia and/or hypertension, if necessary. The study used a primary composite end point that included any stroke in the same territory as the presenting event within 1 year of randomization and “hard TIA” in the same territory as the presenting event from 2 days to 1 year after randomization. Among 29 patients who met one of the primary end points within 1 year of randomization, 8 (15.1%) patients were in the medical group and 21 (36.2%) were in the stent group (risk difference, 21.1%; 95% CI, 5.4% to 36.8%; p=0.02). The rates of stroke within 30 days of randomization or TIA were 9.4% in the medical group and 24.1% in the stent group (risk difference, 14.7%; 95% CI, 1.2% to 28.2%; p=0.05). The 30-day all-cause mortality rate was 5.2% and 0% in the stent and the medical groups, respectively (risk difference, 5.2%; 95% CI, -0.5% to 10.9%; p=0.25). The authors concluded that results did not support the use of a balloon-expandable stent for patients with symptomatic intracranial stenosis.

The SAMMPRIS trial was an RCT comparing aggressive medical management alone to aggressive medical management plus stenting in patients with symptomatic cerebrovascular disease (CVD) and an intracranial stenosis between 70% and 99%. (95) This trial used the Wingspan™ stent system implanted by experienced neuro-interventionalists credentialed to participate in the trial. The authors planned to enroll 750 patients based on power calculations. However, the trial was stopped early for futility after 451 patients had been randomized, due to an excess of the primary outcome (stroke or death) at 30 days in the stenting group. In the stenting group, the rate of stroke or death at 30 days was 14.7% (95% CI, 10.7% to 20.1%) compared with 5.8% (95% CI, 3.4% to 9.7%; p=0.002) in the medical management group. At the time of trial termination, mean follow-up was 11.9 months. Kaplan-Meier estimates of the primary outcome of stroke or death at 1 year was 20.5% (95% CI, 15.2% to 26.0%) in the stenting group and 12.2% (95% CI, 8.4% to 17.6%; p=0.009) in the medical management group. These results represented an excess rate of early AEs with stenting over what was expected together with a decreased rate of stroke and death in the medical management group compared with expected values.

The SAMMPRIS investigators also published results from long-term subject follow-up.96 Primary end points (in addition to stroke or death within 30 days of enrollment) included ischemic stroke in the qualifying artery beyond 30 days after enrollment or stroke or death within 30 days after a revascularization procedure of the qualifying lesion. During a median follow-up of 32.4 months, 34 (15%) of 227 of patients in the best medical management group and 52 (23%) of 224 patients in the stenting group had a primary end point event, with a significantly higher cumulative probability of a primary end point in the stenting group than in the best medical management group (p=0.025). Compared with the best medical management group, subjects in the stenting group had higher rates of any stroke (59/224 [26%] versus 42/227 [19%], p=0.047) and major hemorrhage (29/224 [13%] versus 10/227 [4%], p<0.001). The authors concluded that the benefits of aggressive medical management over percutaneous angioplasty and stenting among patients with intracranial stenosis persist over long-term follow-up.

In 2015, Lutsep et al. published a subgroup analysis of the SAMMPRIS trial results to evaluate whether outcomes differed for patients whose qualifying events occurred on or off antithrombotic therapy. (97) Similar to the overall trial results, outcomes were worse in the stent group than in the best medical management group: of the 284 patients on antithrombotic therapy at the time of the qualifying event, 140 patients were randomized to medical management and 144 to stenting; in Kaplan-Meier analysis, 2-year rates of the primary end point were 15.6% in the medical management group and 21.6% in the stent group (p=0.043). In other subgroup analyses of the SAMMPRIS trial results, 2-year event rates were higher in the stent group for most variables evaluated. (98) The interaction between treatment and the subgroup variables was not significant for any variable.

The CAVATAS randomized 16 patients with symptomatic vertebral artery stenosis to endovascular therapy (balloon angioplasty or stenting) or best medical treatment alone. (99) Endovascular intervention was technically successful in all 8 patients, but 2 patients experienced TIAs during endovascular treatment. During a mean follow-up of 4.7 years, no patient in either treatment group experienced a vertebrobasilar territory stroke, but 3 patients in each arm died of myocardial infarction (MI) or carotid territory stroke, and 1 patient in the endovascular arm had a nonfatal carotid territory stroke. The investigators concluded that patients with vertebral artery stenosis were more likely to have carotid territory stroke and MI during follow-up than recurrent vertebrobasilar stroke. While they noted the trial failed to show a benefit of endovascular treatment of vertebral artery stenosis, the small number of patients enrolled severely limits conclusions.

In 2013, Qureshi et al. published results from another small RCT comparing angioplasty alone to angioplasty plus a balloon-expanding stent among 18 subjects with moderate intracranial stenosis (≥50%) with documented failure of medical treatment or severe stenosis (≥70%) with or without failure of medical treatment. (100) Technical success (<30% residual stenosis on immediate postprocedure angiography) occurred in 5 of 10 patients treated with angiography (9 randomized to angiography, 1 crossover from group randomized to stent placement) and 5 of 8 patients treated with stent placement. Rates of stroke or death were low in both groups: 1 of 10 in the angiography group and none in the stent placement group. This study suggests that angioplasty with stenting is feasible in patients with severe intracranial stenosis, but the small sample size and lack of statistical comparisons limit conclusions that can be drawn.

Systematic Reviews

Before publication of the SAMMPRIS trial results, several systematic reviews addressed the role of stenting for intracranial atherosclerosis, which generally concluded that additional evidence from RCTs would be needed to conclude that stenting should be used in practice. (101-103)

In 2016, Abuzinadah conducted a systematic review and meta-analysis of studies reporting the rates of stroke recurrence or death (the primary outcome) in symptomatic intracranial vertebrobasilar stenosis with medical or endovascular treatment. (104) The authors identified 23 studies involving 592 medical treatment patients and 480 endovascular treatment patients. In pooled analysis, the stroke or death rates were 14.8 per 100 person-years (95% CI, 9.5 to 20.1) in the medical therapy group and 8.9 per 100 person-years (95% CI, 6.9 to 11.0) in the endovascular group (incidence rate ratio [IRR], 1.3; 95% CI, 1.0 to 1.7). The stroke recurrence rates were 9.6 per 100 person-years (95% CI, 5.1 to 14.1) in the medical group and 7.2 per 100 person-years (95% CI, 5.5 to 9) in the endovascular group (IRR=1.1; 95% CI, 0.8 to 1.5).

Nonrandomized Comparative Studies

A number of nonrandomized retrospective or registry-based studies provided relatively weak evidence on the comparative efficacy of endovascular procedures versus medical therapy for intracranial atherosclerosis (e.g., Tang et al., [105] Qureshi et al., [106] Samaniego et al. [107]).

Section Summary: Endovascular Interventions for Symptomatic Intracranial Atherosclerotic Disease

The strongest evidence on the efficacy of endovascular treatment for symptomatic intracranial stenosis is from the SAMMPRIS and VISSIT RCTs. The SAMMPRIS trial was stopped early due to harms, because the rate of stroke or death at 30 days following treatment was higher in the endovascular arm, which received percutaneous angioplasty with stenting. Follow-up of the SAMMPRIS subjects has demonstrated no long-term benefit from endovascular therapy. The VISSIT RCT similarly found no benefit with endovascular treatment. These studies support the conclusion that outcomes of endovascular treatment are worse than medical therapy in patients with symptomatic intracranial stenosis.

Stent-Assisted Endovascular Treatment of Intracranial Aneurysms

Self-Expanding Stent-Assisted Coiling for Intracranial Aneurysms

Three self-expanding stents, the Neuroform™ Microdelivery Stent System, the Enterprise™ Vascular Reconstruction Device and Delivery System, and the Low-Profile Visualized Intraluminal Support Device, have FDA approval through the HDE program for the endovascular treatment intracranial aneurysms. The literature search did not identify any randomized trials of self-expanding stent-assisted treatment of intracranial aneurysms compared with standard neurosurgical treatment (i.e., surgical clipping or endovascular coils). The available evidence includes single-arm case series, registry studies, nonrandomized comparative studies, and a systematic review of nonrandomized comparative studies.

Systematic Reviews and Meta-Analyses

In 2014, Hong et al. reported results of a systematic review and meta-analysis of studies that compared stent-assisted coiling with coiling alone for the treatment of intracranial aneurysms. (108) The authors included 10 retrospective cohort studies, ranging in size from 9 to 1109 patients. In pooled analysis, compared with coiling alone, stent-assisted coiling was associated with higher rates of progressive thrombosis (37.5% versus 19.4%; OR=2.75; 95% CI, 1.95 to 3.86; p<0.000) and lower rates of recurrence (16.2% versus 34.4%; OR=0.35; 95% CI, 0.25 to 0.49; p<0.000). Mortality was 9.1% for stent-assisted coiling compared with 2.6% for coiling alone, although the difference was not statistically significant (OR=2.31; 95% CI, 0.68 to 7.82; p=0.18). Similarly, permanent complication rates and thromboembolic complication rates did not differ significantly between the 2 groups.

In 2015, Ryu et al. conducted a systematic review of studies reporting complications after stent-assisted coiling of ruptured intracranial aneurysms, with a focus on complications related to antiplatelet therapy. (109) The review included 33 studies, 3 of which were prospective and the remaining 30 retrospective (total N=1090 patients). In pooled analysis, thromboembolic complications occurred in 108 patients (event rate, 11.2%; 95% CI, 9.2% to 13.6%). Intraprocedural hemorrhage occurred in 46 (event rate, 5.4%; 95% CI, 4.1% to 7.1%).

Nonrandomized Comparative Studies

The largest comparative series describing use of stents and coiling alone for treating intracranial aneurysms was described by Piotin et al. (110) They report on a series of 1137 patients (1325 aneurysms) treated between 2002 and 2009. In this series, 1109 (83.5%) aneurysms were treated without stents (coiling) and 216 (16.5%) were treated with stents (15 balloon-expandable and 201 self-expandable stents). Permanent neurologic procedure-related complications occurred in 7.4% (16/216) of those with stents versus 3.8% (42/1109) of those without stents (logistic regression p=0.644; OR=1.289; 95% CI, 0.439 to 3.779). Procedure-induced mortality occurred in 4.6% (10/216) of the procedures with stents versus 1.2% (13/1109) in those without (logistic regression p=0.006; OR=0.116; 95% CI, 0.025 to 0.531). At the time of publication, the authors had followed 53% (114/216) of aneurysms treated with stents and 70% (774/1109) of aneurysms treated without, with angiographic recurrence in 14.9% (17/114) versus 33.5% (259/774), respectively (p<0.001; OR=0.349; 95% CI, 0.204 to 0.596).

Additional smaller nonrandomized comparative studies, both prospective and retrospective, have evaluated stent-assisted coiling, compared to coiling alone, balloon-assisted coiling, or surgical clipping.

Hetts et al. compared outcomes for patients treated with stent-assisted coiling and those treated with coiling alone for patients with unruptured intracranial aneurysms enrolled in the prospective, nonrandomized, multicenter MAPS Trial. (111) The trial compared bare-metal aneurysm coils and polymer-coated aneurysm coils. One-hundred thirty-seven patients received a stent-assisted coil and 224 patients received coiling alone. Patients treated with stent-assisted coiling more often had wide-neck aneurysms (62% versus 33%; p<0.000) and had aneurysms with lower dome-to-neck ratio (1.3 versus 1.8; p<0.000). Periprocedural serious AEs occurred in 6.6% of those treated with stent-assisted-coiling, compared with 4.5% of those treated with coiling alone (p=0.039). At 1 year, ischemic strokes were more common in patients who received a stent-assisted coil than in patients who received a coil alone (8.8% versus 2.2%; p=0.005). However, in multivariable analysis, stent use did not independently predict ischemic stroke at 2 years (adjusted OR=1.1; p=0.94).

Consoli et al. compared stent-assisted coiling with balloon-assisted coiling in patients with unruptured wide-necked intracranial aneurysms treated at a single center. (112) The study included 268 patients (286 aneurysms), 117 (122 aneurysms) of whom were treated with stent-assisted coiling and 151 (164 aneurysms) of whom were treated with balloon-assisted coiling. At discharge, 97.9% and 97.3% of those in the balloon-assisted and stent-assisted groups, respectively, had mRS scores of 0 or 1 (statistical comparison not reported). After 6 months, 97.9% and 98% of those in the balloon-assisted and stent-assisted groups, respectively, had mRS score of 0 or 1, while mortality rates were 2.6% and 1.7% in the balloon-assisted and stent-assisted groups, respectively (statistical comparisons not reported). At 6 months, aneurysm recurrence rates were 11.1% and 5.8% in the balloon-assisted and stent-assisted groups, respectively. In multivariable analysis, the use of stent-assisted coiling was significantly associated with complete occlusion at the end of the procedure (regression coefficient not reported; p=0.024) and complete occlusion after 6 months (regression coefficient not reported; p=0.05).

A nonrandomized comparative study from Korea reported on 126 aneurysms treated with stent-assisted coiling and 86 treated with coil alone. (113) At 2-year follow-up, the authors reported rates of occlusion and recurrence. Progressive occlusion was noted in 42.5% (17/40) of the stent group and 39.5% (34/86) of the nonstented group (p=NS). The rates of aneurysm recurrence also did not differ statistically between groups. There was aneurysm recurrence in 17.5% of patients in the stent group and 21.0% in the nonstent group.

Liu et al. retrospectively compared outcomes for patients with posterior communicating artery aneurysms treated with stent-assisted coiling to those treated with coiling alone. (114) A total of 291 coiling procedures were performed, including 56 aneurysms treated with a self-expandable stent. Complete aneurysm occlusion on initial angiography occurred in 41.1% of stent-assisted coiling patients compared with 35.3% of nonstented patients (statistical comparison not reported). At last follow-up (mean, 14.3 months for stent-assisted coiling and 13.2 months for nonstent patients), aneurysms recurred in 10.6% of stent-assisted coiling patients compared with 28.1% of nonstent patients (p=0.014). Procedural complications occurred in 10.7% of stent-assisted coiling patients compared with 11.5% of nonstent patients (p=NS).

Colby et al. reported on 90 consecutive patients undergoing treatment for para-ophthalmic aneurysms, 30 of whom were treated with coil alone and 60 with stent-assisted coils. (115) On initial angiography following the procedure, complete occlusion of the aneurysm was achieved in 43.3% of stented patients compared with 31.7% of nonstented patients. At a mean 14.5-month follow-up, the recurrence rate was lower for the stented group (15.4% [4/26]) than in the nonstented group (41.5% [17/41]; p<0.05).

Comparison Between Endovascular Devices for Intracranial Aneurysms

Nonrandomized studies, summarized in a 2015 systematic review by King et al., have compared devices used for stent-assisted coiling of intracranial aneurysms. (116) King et al. reviewed published studies reporting on stent-assisted coiling with the Neuroform and Enterprise systems to assess outcomes between the devices. The analysis included 47 studies with a total of 4039 patients (4238 aneurysms; 2111 treated with Neuroform and 2127 with Enterprise). Most (81%) studies were retrospective. Compared with those treated with the Enterprise system, patients treated with the Neuroform system were more likely to have deployment failure (2.3% versus 0.2%, p<0.001) and have a higher mortality rate (2.8% versus 1.8%, p=0.04), less likely to have 100% aneurysm occlusion at last follow-up (61.1% versus 74.7%, p<0.001), and more likely to have recanalization (13.9% versus 10.6%, p=0.02). However, conclusions drawn from these findings are influenced by the potential for bias in the underlying studies and between-study heterogeneity.

Single-Arm Series

A large number of single-arm series have reported outcomes for stent-assisted coiling.

Systematic Reviews

A systematic review by Shapiro et al. identified 39 articles (total N=1517 patients), most of which were single-arm, retrospective series. (117) Most patients treated had unruptured aneurysms, but 22% had ruptured aneurysms. The authors noted a large amount of heterogeneity in reporting outcomes data, particularly for AEs. The periprocedural mortality rate was 2.1%, and the overall complication rate was 19%. Immediately after treatment, approximately 45% of patients had occlusion of the aneurysm. At an average of 13 months’ posttreatment, the stroke rate in the stented area was 3.2%.

A systematic review focusing only on ruptured aneurysms was published by Bodily et al. in 2011. (118) This review selected 17 articles that described treatment in 212 patients. Technical success was high (93%), and 2% of patients required open surgery due to stent failure or intraoperative aneurysm rupture. Sixty-three percent (130/207) of aneurysms were successfully occluded. The overall mortality rate was 19%, and 14% of patients had poor clinical outcomes. A relatively high rate of AEs was reported, with 8% of patients having acute procedure-related intracranial bleeding and 6% (16/288) having a clinically significant thromboembolic event.

Nonrandomized Comparative Studies

Since publication of the Shapiro and the Bodily reviews, a number of noncomparative studies evaluating the use of stent-assisted endovascular treatments in intracranial aneurysms have been published.

The largest study, reported by Geyik et al., included 468 patients with wide-necked cerebral aneurysms who underwent stent-assisted coiling with the Enterprise™, Neuroform™, Wingspan™, or (self-expanding) LEO (Balt Extrusion, Montmorency, France) stents. (119) Overall mortality was 1.9%; procedure-related complications occurred in 28 (6.9%) patients. Angiographic follow-up data, obtained from 6 months to 7 years postprocedure (mean, 19.2 months), were available for 440 patients (94%). For the total of 467 aneurysms with follow-up, complete occlusion occurred in 194 aneurysms (41.6%), near-complete occlusion (>95% occlusion but minimal residual filling with coils at the neck) occurred in 242 aneurysms (51.8%), and incomplete occlusion (<95%) occurred in 31 (6.6%) aneurysms. At 6-month follow-up, recanalization occurred in 38 aneurysms (8% of all aneurysms with follow-up available). The authors concluded that stents were associated with high rates of occlusion and low rates of recurrence over long-term follow-up.

In another relatively large study, Lee et al. reported on 1038 patients treated with endovascular coiling, 296 of whom underwent stent-assisted coiling, with a focus on predictors of procedural rupture. (120) Three cases of procedural rupture occurred among patients treated with stent-assisted coiling.

Other representative noncomparative studies in which at least some patients were treated with devices commercially available in the U.S. are summarized in Table 10. Interpretation of these studies is limited by potential selection bias and no comparison groups. In general, these series demonstrate high rates of technical success of stent deployment with high rates of aneurysm occlusion; however, variable complication rates, particularly related to thromboembolic events, were observed.

Table 10. Noncomparative Studies of Stent-Assisted Endovascular Treatment of Aneurysms

Study

Study Type

Patient Population

Intervention

Primary Outcome

Feng et al. (2016)

(121)

Retrospective case series

97 patients with intracranial saccular aneurysms (13 with rupture)

Endovascular treatment with low profile visualized intraluminal support

All patients had technically successful treatment

98.9% met the primary end point of safety (absence of new transient or permanent neurologic deficit or death)

Over mean 7.8-mo FU, no patient had new neurologic deterioration or died

Among 76 patients with digital angiography imaging at follow up, 59.21% had complete occlusion

Aydin et al. (2015)

(122)

Retrospective case series

80 patients with wide-necked intracranial aneurysm (3 institutions)

Endovascular treatment with stent placement (LEO Baby stent)

97.5% of patients had technically successful treatment

7.5% had periprocedural or delayed thromboembolic events; 3 (3.8%) patients had permanent neurologic deficits

Chalouhi et al. (2013) (123)

Retrospective case series

76 patients with posterior cerebellar artery aneurysms at a single institution

Endovascular coiling, with or without Neuroform™ stent assistance (4 patients) or balloon assistance (4 patients)

93.4% of patients had technically successful treatment; remaining patients required surgical clipping

Among 67 patients who had successful endovascular treatments and who did not die in the hospital, favorable outcomes (mild, moderate, no disability) were achieved in 85%

Chen et al. (2013) (124)

Retrospective case series

10 patients with large and giant fusiform aneurysms of the vertebrobasilar arteries at a single institution

Endovascular treatment with stent placement (Neuroform™ or LEO [self-expanding, Balt, Montmorency, France], 5 patients), stent-assisted coiling (3 patients), or occlusion of proximal artery (2 patients)

9 patients had a good outcome; 1 patient died after stenting procedure.

Stent deployment was generally feasible in the vertebrobasilar system

Gentric et al. (2013) (125)

Prospective cohort; industry-sponsored

107 patients with unruptured cerebral aneurysms enrolled at one of 10 European institutions

Endovascular treatment with Neuroform stent-assisted coiling

94.4% of patients had technically successful treatment. 66.4% of patients had complete occlusion immediately postprocedure

At follow up at 12-18 months, 5 patients (5%) had delayed complications, with 3% of patients with thromboembolic events

Of 93 patients with anatomic evaluation available, aneurysms recurred in 9.7%

Johnson et al. (2013) (126)

Retrospective case series

91 patients with complex middle cerebral artery aneurysms not amenable to coiling enrolled at a single institution

Endovascular treatment with coiling with stent assistance using Neuroform™ (62 aneurysms), Enterprise™ (32 aneurysms), Wingspan™ (1 aneurysm), or a combination (5 aneurysms) or with stenting along (2 aneurysms), endovascular treatment with stenting alone

All patients had technically successful treatment

9 patients had new neurologic symptoms following the procedure, one with long-term disability. There was 1 procedure-related death

Of 85 aneurysms with initial follow-up imaging available (usually at 6 months postprocedure), 77 (90.6%) were completely occluded, and 4 (4.7%) required retreatment

Kulcsar et al. (2013) (127)

Retrospective case series

117 patients with wide-necked cerebral aneurysms

Endovascular treatment with Neuroform stent-assisted coiling

Stents were successfully deployed in 113 patients with 117 aneurysms

99 patients had grade 1 or 2 occlusion (complete or aneurysm neck) on immediate postprocedure imaging

Intra-procedure major thrombotic events occurred in 7 cases (5.9%) and major infarcts on postprocedure imaging in 9 cases (7.7%)

Of 92 aneurysms with follow-up imaging available, 71 (77%) had grade 1 or 2 occlusion

Section Summary: Self-Expanding Stent-Assisted Coiling for Intracranial Aneurysms

There is a lack of RCT evidence on the efficacy of self-expanding stent-assisted coiling compared with coiling alone or surgical clipping for the treatment of intracranial aneurysms. Nonrandomized studies have reported higher complete occlusion rates with stenting and lower recurrence rates. However, some evidence shows that AE rates are relatively high with stenting, and 1 nonrandomized comparative trial reported higher mortality with stent-assisted coiling than with coiling alone. This evidence is insufficient to determine whether stent-assisted coiling improves outcomes for patients with intracranial aneurysms because the risk-benefit ratio cannot be adequately defined. However, it is recognized that patients who are candidates for endovascular therapy for aneurysms frequently have aneurysms in locations that are not amenable to surgical therapy, making comparisons to surgical therapy unlikely. Given the relative rarity of intracranial aneurysms, there may be legitimate barriers to clinical trials.

Flow-Diverting Stents for Intracranial Aneurysms

In 2011, the Pipeline Embolization Device, which is categorized as a flow-diverting stent, received FDA premarket approval. The device’s approval was based on the industry-sponsored PUFA study, a multicenter, prospective, single-arm trial of the device for treatment of ICA aneurysms that were uncoilable or had failed coiling. (11) Investigators enrolled 108 patients at 10 centers with unruptured large- or giant-necked aneurysms measuring at least 10 mm in diameter, with aneurysm necks of at least 4 mm, who underwent placement of 1 or more Pipeline devices. One patient was excluded from evaluations of the device effectiveness and safety due to unsuccessful catheterization. Four patients were excluded from evaluation of the device effectiveness. Two patients had 2 qualifying aneurysms treated, so the “effectiveness cohort” was 106 aneurysms in 104 patients. Seventy-eight (73.6%) of 106 aneurysms met the study’s combined primary effectiveness end point of complete occlusion at day 180 without major stenosis or use of adjunctive coils. For 6 (5.6%) of the 107 patients who underwent any catheterization, a primary safety end point (occurrence of major ipsilateral stroke or neurologic death at 180 days) occurred.

The literature search did not identify any randomized trials of flow-diverting stent treatment of intracranial aneurysms compared with standard neurosurgical treatment (i.e., surgical clipping or endovascular coils). The available evidence related to the use of flow-diverting stents consists of several nonrandomized comparative study and multiple single-arm case series.

Nonrandomized Comparative Studies

Zhou et al. reported results of a systematic review of studies comparing flow-diverting devices with endovascular coiling for intracranial aneurysms, which included 9 retrospective comparative studies (total N=863 subjects). (128) This review included studies of patients with ruptured or unruptured aneurysms. Across the 9 studies, 305 patients were treated with flow-diverting devices, 558 with coil embolization therapy, and 324 with stent-assisted coiling alone. In pooled analysis, the use of flow- diverting devices was associated with a significantly higher complete occlusion rate compared with coil embolization therapy (OR=3.13; 95% CI, 2.11 to 4.65; I2=18%) or with stent-assisted coiling (OR=2.08; 95% CI, 1.34 to 3.24; I2=0%). Rates of overall morbidity did not differ significantly between patients treated with flow-diverting devices and coil embolization therapy, or between flow-diverting devices and stent-assisted coiling.

In a 2014 study, not included in the Zhou review and included more patients than any single study in that review, van Rooij et al. reported outcomes for 550 consecutive patients treated with endovascular methods for intracranial aneurysms at a single European center from 2009 to 2013. (129) Endovascular treatments consisted of selective coiling in 445 (80.8%) patients, stent-assisted coiling in 68 (12.4%), balloon-assisted coiling in 13 (2.4%), parent vessel occlusion in 12 (2.2%), and flow-diverter treatment in 12 (2.2%). Among the 11 patients treated with flow diverters, 2 patients had ruptured dissecting aneurysms, 2 died, 1 patient had permanent morbidity, and 2 aneurysms were not occluded at 30-month follow-up. Direct comparisons with outcomes from alternative treatments were not reported.

Single-Arm Series

Systematic Reviews and Meta-Analyses

Multiple noncomparative studies have reported outcomes from flow-diverting stent-assisted treatment of intracranial aneurysms since the introduction of the Pipeline endovascular device. These studies have been summarized in several systematic reviews and meta-analyses. The largest systematic review identified (reported by Briganti et al. in 2015) reviewed 18 studies published from 2009 to 2014 (total N=1483 patients; 1704 aneurysms). (130) Most (87.5%) treated aneurysms were in the anterior circulation and most (87.5%) were saccular in morphology. In the 17 studies reporting procedural complications, mean incidence was 8.3% (range, 0%-23.1%). Permanent morbidity occurred in a mean 3.5% of patients (range, 0%-15%), while the mean mortality rate was 3.4% (range, 0.5%-8%). Across the 18 studies, aneurysms were completely occluded in a mean 81.5% of cases (range, 69%-100%).

Earlier systematic reviews by Brinjikji et al. (2013) (131) and Arrese et al. (2013) (132) similarly reported high estimates for aneurysm occlusion rates (»75%), but relatively high rates of morbidity and mortality.

Noncomparative Studies

Since those reviews, a number of noncomparative studies evaluating flow-diverting stents in the treatment of aneurysms have been published. The largest cohort study identified was by Kallmes et al., who conducted a retrospective analysis of patients treated with the Pipeline device at 17 centers worldwide. (133) The authors identified 793 patients with 906 aneurysms who were enrolled in the International Retrospective Study of Pipeline Embolization Device (IntrePED) registry. Of the total number of aneurysms, 311 were in the anterior ICA circulation and at least 10 mm, 349 of which were in the anterior circulation and less than 10 mm, 59 of which were in the posterior circulation, 179 of which were in a non-ICA anterior circulation location and less than 10 mm, and 10 of which had no aneurysm size specified. Overall neurologic morbidity and mortality was 8.4%, highest in the posterior circulation group (16.4%) and lowest in the less than 10-mm ICA group (4.8%; p=0.01). The overall spontaneous rupture rate was 0.6%, and the intracranial hemorrhage rate was 2.4%. Ischemic stroke rates were 4.7%, again highest in the posterior circulation group (7.3%) and lowest in the less than 10-mm ICA group (2.7%; p=0.16). In a subsequent study using data from the same registry, Brinjikji et al. reported on risk factors for hemorrhagic complications after Pipeline device placement. (134) Twenty patients had an intraparenchymal hemorrhage, most often (75%) within 30 days of treatment. The only procedure- or device-related variable associated with intraparenchymal hemorrhage was receiving 3 or more Pipeline devices (OR=4.10; 95% CI, 1.34 to 12.58; p=0.04). Additional analyses from this registry have evaluated the effect of age on outcomes after Pipeline placement (135) and differences in complication rates between aneurysms treated with the Pipeline with or without coil embolization. (136)

The longest follow-up reported is from a series of 98 patients with 119 aneurysms treated with the Pipeline Embolization Device and followed for at least 2 years. (137) Of the 119 aneurysms, all had clinical follow-up and 88.8% had imaging follow-up for 2 or more years postprocedure. aneurysm occlusion rates were 81.6%, 84.1%, and 93.2% at 6-month, 1-year, and 2-year follow-ups, respectively. Three (2.8%) cases of in-stent stenosis occurred. From 0 to 6 months, rates of TIA, minor stroke, and major stroke were 4.2%, 3.4%, and 0.8%, respectively.

Guedon et al. reported on late ischemic complications after flow-diverting stent placement. (138) Among 86 patients treated at a single institution, mean angiographic follow up was available to 15.7 months (SD=11.8 months; range, 8-21 months) and mean clinical follow-up was available to 16.9 months (SD=12.9 months; range 10-22 months). Five (5.8%) patients developed ischemic complications.

Additional representative studies, with a focus on series including more than 50 patients, are summarized in Table 11.

Table 11. Noncomparative Studies of Flow-Diverting Stent-Assisted Endovascular Treatment of Aneurysms

Study

Study Type

Patient Population

Intervention

Primary Outcome

Strauss et al. (2016)

(139)


 

Retrospective case series

60 patients with anterior or posterior circulation aneurysms (67 aneurysms)

Silk flow-diverting stent (Balt Extrusion, Montmorency, France)

 

• 10 patients had periprocedural complications, 4 of whom died

• Among 60 aneurysms with available follow up imaging (median, 15-month post-treatment), 88% had good angiographic results (complete or near-complete occlusion)


 

Fischer et al. (2015)

(140)


 

Retrospective case series

121 patients with intracranial saccular sidewall aneurysms (130 aneurysms)

P64 Flow-Modulated Device (Phenox, Bochum, Germany)

 

• 1 patient had pulmonary artery embolism and 2 patients had ischemic lesions with transient neurologic deficits in the periprocedural period

• Among 93 aneurysms with available diffusion-weight imaging (median, 279 d), 79.6% had complete aneurysm occlusion

 

Brasiliense et al. (2016)

(141)

 

Prospective case series

59 patients (70 aneurysms) who underwent routine postprocedural magnetic resonance imaging after placement of flow diversion

Pipeline Embolization Device

 

• 5.1% had clinically apparent neurologic symptoms postprocedure

• 62.7% had ischemic lesions on diffusion-weight imaging postprocedure

 

Chalouhi et al. (2015)

(142)


 

Retrospective case series

100 patients with aneurysms ≤7 mm (1 institution)

Pipeline Embolization Device

 

• Complications in 3% (1 distal parenchymal hemorrhage, 2 ischemic events)

• At last follow up (mean, 6.3 months), 72% of aneurysms completely occluded

• Retreatment required in 8%

 

Lubicz et al. (2015) (143)

 

Retrospective review of prospectively collected data

 

58 patients with 70 intracranial aneurysms treated at 2 institutions

SILK artery reconstruction device (Balt Extrusion, Montmorency, France)

 

• No periprocedural deaths occurred

• Overall permanent neurologic morbidity was 5.5%

• At long-term follow up, 73% had complete occlusion, 16% had neck remnants, 11% had incomplete occlusion

 

Wakhloo et al. (2015) (144)

 

Prospective multicenter trial at 24 centers

 

165 patients with 190 intracranial aneurysms

 

Surpass flow diverting device (Stryker Neurovascular, Fremont, CA)

 

• At 6-mo follow up, permanent neurologic morbidity was 6% and permanent neurologic mortality was 2.7%

• Neurologic death during follow up occurred in 1.6% of patients with anterior circulation aneurysms and 7.4% with posterior circulation aneurysms

• Ischemic stroke at ≤30 d, sub-arachnoid hemorrhage at ≤7 d, and intraparenchymal hemorrhage at ≤7 d occurred in 3.7%, 2.5%, and 2.5% of subjects, respectively

 

Kan et al. (2013) (145)

Prospective case series (registry)

56 patients with intracranial aneurysm treated at 7 institutions

Pipeline Embolization Device placement

 

• 6/123 devices incompletely deployed

• Among 19 patients with 6-month follow-up, 68% (13 patients) had complete aneurysm occlusion

• 4 fatal postprocedural hemorrhages occurred

 

Piano et al. (2013) (146)

Retrospective case series

101 patients with intracranial aneurysm at a single institution

Flow-diverting stent placement (Pipeline Embolization Device or SILK device), with or without endovascular coiling

86% of aneurysms evaluated at 6-month follow-up showed complete occlusion

Toma et al. (2013) (147)

Retrospective case series

84 patients with intracranial aneurysm at a single institution

Flow-diverting stent placement

61% of aneurysms had resolved at 12 months

9.5% of patients had a new, permanent neurologic deficit and 5.9% of patients had procedure-related mortality

Section Summary: Flow-Diverting Stents for Intracranial Aneurysms

No RCTs have evaluated flow-diverting stents. One nonrandomized study comparing the flow-diverting stents with endovascular coiling for intracranial aneurysms, demonstrated higher rates of aneurysm obliteration in those treated with the Pipeline endovascular device than in those treated with coiling, with similar rates of good clinical outcomes. Single-arm series have suggested that there are high rates (70%+) of aneurysmal occlusion after flow-diverting stent placement. As for self-expanding stents for aneurysms, patients who are candidates for endovascular therapy for aneurysms frequently have aneurysms in locations amenable to surgical therapy, making comparisons to surgical therapy unlikely. Given the relative rarity of intracranial aneurysms, there may be legitimate barriers to clinical trials.

Ongoing and Unpublished Clinical Trials

Some currently unpublished trials that might influence this review are listed in Table 12.

Table 12. Summary of Key Trials

NCT Number

Trial Name

Planned Enrollment

Completion Date

Endovascular interventions for acute ischemic stroke

Ongoing

NCT01852201

POSITIVE: Perfusion Imaging Selection of Ischemic Stroke Patients for Endovascular Therapy

750

May 2016

NCT01983644

RECO Flow Restoration Device Versus Intravenous t-PA for Stroke Within 4.5h of Symptom Onset: a Prospective Randomized Control Trial (RESTORE)

130

Nov 2016

NCT01429350a

The THERAPY Trial: The Randomized, Concurrent Controlled Trial to Assess the Penumbra System's Safety and Effectiveness in the Treatment of Acute Stroke

692

Dec 2016

NCT02216643

Randomization of Endovascular Treatment with Solitaire™ FR versus Best Medical Therapy in Acute Ischemic Stroke Due to Large Vessel Occlusion Trial

690

Mar 2018

NCT02157532

Intra-arterial Thrombectomy as an Acute Treatment Intervention for Stroke: The Endovascular Acute Stoke Intervention (EASI) Trial

480

Jan 2020

Unpublished

NCT01455935

Wake up Symptomatic Stroke in Acute Brain Ischemia (WASSABI) Trial

90

Feb 2014 (unknown)

NCT01869478

Endovascular Arterial Reperfusion versus. Intravenous Thrombolysis for Acute Ischemic Stroke (EARLY): A Randomized Pilot Study of Ultra-early (2 Hours) and Early (2-4.5 Hours) Reperfusion Therapy

20

Sep 2015 (unknown)

Endovascular interventions for symptomatic intracranial atherosclerotic disease

Ongoing

NCT01763320

China Angioplasty & Stenting for Symptomatic Intracranial Severe Stenosis (CASSISS): A Prospective Multicenter, Randomized Controlled Trial

380

Dec 2017

Unpublished

NCT00816166

Phase III Study of Pharos Vitesse Neurovascular Stent System Compared to Best Medical Therapy for the Treatment of Ischemic Disease

250

Terminated

Stent-assisted endovascular treatment of intracranial aneurysms

Ongoing

NCT01340612

Stenting in the Treatment of Aneurysm Trial (STAT)

600

Apr 2016

NCT01349582

Flow Diversion in Intracranial Aneurysm Treatment (FIAT)

344

Apr 2017

NCT01811134

Flow Diverter Stent for Endovascular Treatment of Unruptured Saccular Wide-necked Intracranial Aneurysms (EVIDENCE)

130

Nov 2017

NCT01762137

LARGE Aneurysm Randomized Trial: Flow Diversion Versus Traditional Endovascular Coiling Therapy

316

Apr 2018

NCT01976026

DIVERT: Diversion of Flow in Intracranial Vertebral and Blood Blister-like Ruptured Aneurysms Trial: A Randomized Trial Comparing Pipeline Flow Diversion and Best-Standard-Treatment

420

Jan 2021

Table Key:

NCT: National Clinical Trial.

a: Denotes industry-sponsored or cosponsored trial.

Clinical Input Received through Physician Specialty Societies and Academic Medical Centers

In 2011 Blue Cross Blue Shield Association (BCBSA) requested and received clinical input from 3 physician specialty societies and 3 academic medical centers. For treatment of intracranial stenosis, the majority of those providing input would consider use of this technology in selected patients who remained symptomatic from intracranial atherosclerotic disease despite maximum medical therapy. There was unanimous support for use of this technology in selected patients with intracranial aneurysms; i.e., in those patients for whom surgical treatment is not possible and for whom endovascular treatment (coils) does not completely isolate the aneurysm.

Again in 2014, BCBSA requested and received clinical input from 4 physician specialty societies and 2 academic medical centers Request for clinical input in 2014 focused on the use of flow-diverting stents such as the Pipeline Embolization Device for the treatment of intracranial aneurysms. There was general support for the use of intracranial stent placement for intracranial aneurysms meeting the criteria outlined in the policy statements. There was also general support for the use of flow-diverting stents for the treatment of intracranial aneurysms and general support for the statement that flow-diverting stents are preferable to other stents for certain aneurysm characteristics. There was general support for the use of endovascular interventions for the treatment of acute stroke, particularly for patients who have failed to respond to IV tPA or who present outside the range of time for which tPA would be considered (within 8 hours of last known normal state or symptom onset).

Practice Guidelines and Position Statements

American Society of Interventional and Therapeutic Neuroradiology (ASITN), the Society of Interventional Radiology (SIR), and the American Society of Neuroradiology (ASNR)

In 2005, ASITN, the SIR, and the ASNR jointly published a position paper on angioplasty and stenting for cerebral atherosclerosis. (148) This position statement reviewed a number of case series and the SSYLVIA and the Wingspan™ multicenter trials. The following position statement was offered, although the underlying rationale and process for development for the position statement were not provided:

“The ASITN, SIR, and ASNR concur that sufficient evidence now exists to recommend that intracranial angioplasty with or without stenting should be offered to symptomatic patients with intracranial stenoses who have failed medical therapy. Endovascular interventions are intensive services provided to patients who are at very high risk for strokes and typically have multiple comorbidities. Similar to revascularization for extracranial carotid artery stenosis, patient benefit from revascularization for symptomatic intracranial arterial stenosis is critically dependent on a low per procedural stroke and death rate and should thus be performed by experienced neuro-interventionists. We recommend reimbursement by third party insurers so that these patients may have access to such interventions. Continued attempts to improve the benefits of endovascular therapy are warranted.”

Society of Interventional Radiology (SIR)

In 2013, SIR issued a position statement on endovascular acute ischemic stroke interventions. (149) SIR’s position statement indicates intra-arterial revascularization for stroke is beneficial when tPA is inappropriate or unsuccessful. SIR indicates, despite clinical trial findings that mechanical thrombectomy is an unproven therapy, rapid treatment with mechanical thrombectomy devices improves outcomes for occlusions in large vessels. The need for clinical trials and/or a national registry is specified.

American Heart Association (AHA)

In 2009, the AHA published a scientific statement on indications for intracranial endovascular neurointerventional procedures. (9) The recommendation related to endovascular treatment of symptomatic intracranial stenoses was noted as class IIb, level of evidence C (usefulness/effectiveness is unknown/unclear). The level of evidence was the same for use of angioplasty and stenting in the treatment of acute ischemic stroke.

American Heart Association (AHA) and American Stroke Association (ASA)

In early 2013, AHA and the ASA published guidelines for the early management of patients with acute ischemic stroke. (3) These guidelines include several recommendations relevant to the use of endovascular therapies for acute stroke:

“Intra-arterial treatment requires the patient to be at an experienced stroke center with rapid access to cerebral angiography and qualified interventionalists. An emphasis on expeditious assessment and treatment should be made. Facilities are encouraged to define criteria that can be used to credential individuals who can perform intra-arterial revascularization procedures. Outcomes on all patients should be tracked (Class I; Level of Evidence C).”

“When mechanical thrombectomy is pursued, stent retrievers such as Solitaire™ FR and Trevo® are generally preferred to coil retrievers such as Merci® (Class I; Level of Evidence A).” The relative effectiveness of the Penumbra System® versus stent retrievers is not yet characterized.

“The Merci®, Penumbra System®, Solitaire™ FR, and Trevo® thrombectomy devices can be useful in achieving recanalization alone or in combination with pharmacological fibrinolysis in carefully selected patients (Class IIa; Level of Evidence B).” Their ability to improve patient outcomes has not yet been established. These devices should continue to be studied in RCTs to determine the efficacy of such treatments in improving patient outcomes.

“Intra-arterial fibrinolysis or mechanical thrombectomy is reasonable in patients who have contraindications to the use of intravenous fibrinolysis (Class IIa; Level of Evidence C).”

“Rescue intra-arterial fibrinolysis or mechanical thrombectomy may be reasonable approaches to recanalization in patients with large-artery occlusion who have not responded to intravenous fibrinolysis. Additional randomized trial data are needed (Class IIb; Level of Evidence B).”

“The usefulness of mechanical thrombectomy devices other than the Merci® retriever, the Penumbra System®, Solitaire™ FR, and Trevo® is not well established (Class IIb; Level of Evidence C).” These devices should be used in the setting of clinical trials.

“The usefulness of emergent intracranial angioplasty and/or stenting is not well established. These procedures should be used in the setting of clinical trials (Class IIb; Level of Evidence C).”

The 2013 guidelines were updated in 2015 to include the results of 8 clinical trials published subsequently. (150) The updated guidelines include the following new or revised recommendations relevant to the use of endovascular therapies for acute stroke:

“Patients should receive endovascular therapy with a stent retriever if they meet all the following criteria (Class I; Level of Evidence A):

o “Prestroke mRS score 0 to 1,

o “Acute ischemic stroke receiving intravenous r-tPA [recombinant tissue plasminogen activator] within 4.5 hours of onset according to guidelines from professional medical societies,

o “Causative occlusion of the internal carotid artery or proximal MCA [middle cerebral artery] (M1),

o “Age ≥18 years,

o NIHSS [National Institutes of Health Stroke Scale] score of ≥6,

o “ASPECTS [Alberta Stroke Program Early Computed Tomography Score] of ≥6, and

o “Treatment can be initiated (groin puncture) within 6 hours of symptom onset.”

“As with intravenous r-tPA, reduced time from symptom onset to reperfusion with endovascular therapies is highly associated with better clinical outcomes. To ensure benefit, reperfusion to TICI [Thrombolysis in Cerebral Infarction] grade 2b/3 should be achieved as early as possible and within 6 hours of stroke onset (Class I; Level of Evidence B-R).”

“When treatment is initiated beyond 6 hours from symptom onset, the effectiveness of endovascular therapy is uncertain for patients with acute ischemic stroke who have causative occlusion of the internal carotid artery or proximal MCA (M1) (Class IIb; Level of Evidence C). Additional randomized trial data are needed.”

“In carefully selected patients with anterior circulation occlusion who have contraindications to intravenous r-tPA, endovascular therapy with stent retrievers completed within 6 hours of stroke onset is reasonable (Class IIa; Level of Evidence C). There are inadequate data available at this time to determine the clinical efficacy of endovascular therapy with stent retrievers for those patients whose contraindications are time-based or non-time based (e.g., prior stroke, serious head trauma, hemorrhagic coagulopathy, or receiving anticoagulant medications).”

“Although the benefits are uncertain, use of endovascular therapy with stent retrievers may be reasonable for carefully selected patients with acute ischemic stroke in whom treatment can be initiated (groin puncture) within 6 hours of symptom onset and who have causative occlusion of the M2 or M3 portion of the MCAs, anterior cerebral arteries, vertebral arteries, basilar artery, or posterior cerebral arteries (Class IIb; Level of Evidence C).”

“Endovascular therapy with stent retrievers may be reasonable for some patients <18 years of age with acute ischemic stroke who have demonstrated large vessel occlusion in whom treatment can be initiated (groin puncture) within 6 hours of symptom onset, but the benefits are not established in this age group (Class IIb; Level of Evidence C).”

“Although the benefits are uncertain, use of endovascular therapy with stent retrievers may be reasonable for patients with acute ischemic stroke in whom treatment can be initiated (groin puncture) within 6 hours of symptom onset and who have prestroke mRS [modified Rankin Scale] score of >1, ASPECTS <6, or NIHSS score <6 and causative occlusion of the internal carotid artery or proximal MCA (M1) (Class IIb; Level of Evidence B-R). Additional randomized trial data are needed.”

“Observing patients after intravenous r-tPA to assess for clinical response before pursuing endovascular therapy is not required to achieve beneficial outcomes and is not recommended. (Class III; Level of Evidence B-R).”

“Use of stent retrievers is indicated in preference to the MERCI device. (Class I; Level of Evidence A). The use of mechanical thrombectomy devices other than stent retrievers may be reasonable in some circumstances (Class IIb, Level B-NR).”

“The use of proximal balloon guide catheter or a large bore distal access catheter rather than a cervical guide catheter alone in conjunction with stent retrievers may be beneficial (Class IIa; Level of Evidence C). Future studies should examine which systems provide the highest recanalization rates with the lowest risk for nontarget embolization.”

“The technical goal of the thrombectomy procedure should be a TICI 2b/3 angiographic result to maximize the probability of a good functional clinical outcome (Class I; Level of Evidence A).”

“Use of salvage technical adjuncts including intra-arterial fibrinolysis may be reasonable to achieve these angiographic results, if completed within 6 hours of symptom onset (Class IIb; Level of Evidence B-R).” However, these data derive from clinical trials that no longer reflect current practice, including use of fibrinolytic drugs that are not available. A clinically beneficial dose of intra-arterial r-tPA is not established, and r-tPA does not have FDA approval for intra-arterial use. As a consequence, endovascular therapy with stent retrievers is recommended over intra-arterial fibrinolysis as first-line therapy (Class I; Level of Evidence E).”

“Intra-arterial fibrinolysis initiated within 6 hours of stroke onset in carefully selected patients who have contraindications to the use of intravenous r-tPA might be considered, but the consequences are unknown (Class IIb; Level of Evidence C).”

Society of Neuro-Interventional Surgery (SNIS)

In March 2015, the SNIS released a report from their Standards and Guidelines Committee regarding embolectomy for stroke with emergent large vessel occlusion. (151) The purpose for the committee research were the results from major study trials in the last 3 years comparing endovascular therapy with standard medical therapy alone. The following are summary and recommendations by the Committee:

“IV [intravenous] thrombolysis should be offered to all eligible patients presenting within 3.0 h [hours] of symptom onset (AHA [American Heart Association] Class I, level of evidence A).

A. Patients who meet the additional criteria also benefit from IV thrombolysis between 3.0 and 4.5 h from symptom onset (AHA Class I, level of evidence B).

B. Intravenous thrombolysis should not be withheld in eligible patients in whom subsequent endovascular therapy is planned.”

“Intra-arterial thrombolysis is reasonable in patients presenting within a major stroke with occlusion of the middle cerebral artery in whom direct catheter access for embolectomy is precluded for anatomic reasons, as long as thrombolysis can be completed within 6 h from symptom onset (AHA Class IIa, level of evidence B).”

“For patients with anterior circulation stroke and documented ELVO [emergent large vessel occlusion] affecting the ICA [internal carotid artery] and M1 [sphenoid] segment of the MCA [middle cerebral artery] and a corresponding deficit, the addition of endovascular embolectomy results in superior clinical outcomes compared with best medical therapy alone. Embolectomy needs to be performed as rapidly as possible for the greatest clinical benefit, and is best when performed within 6 h from onset of symptoms (AHA Class I, level of evidence A.”

American Association of Neurological Surgeons (AANS)

The AANS have not released a practice guideline, but released in March 2015 a recommendation position following the results of the MR CLEAN endovascular therapy trial, “The MR CLEAN study confirms that it is no longer ethical to deny ELVO patients a treatment that can prevent disability or death.” (152)

Summary of Evidence

The evidence for the use of endovascular mechanical embolectomy in individuals who have acute ischemic stroke due to occlusion of an anterior circulation vessel includes randomized clinical trials (RCTs) comparing endovascular therapy with standard care and systematic reviews of these RCTs. Relevant outcomes are overall survival, morbid events, functional outcomes, and treatment-related mortality and morbidity. From 2013 to 2015, 8 RCTs were published comparing endovascular therapies with noninterventional care for acute stroke in patients with anterior circulation occlusions. The 5 more recent trials (published from 2014 to 2015) all demonstrated a significant benefit in terms of reduced disability at 90 days’ posttreatment. The trials that demonstrated a benefit to endovascular therapy either exclusively used stent retriever devices or allowed the treating physician to select a device, mostly a stent retriever device, and had high rates of mechanical embolectomy device use in patients randomized to endovascular therapy. All studies that demonstrated a benefit to endovascular therapy required demonstration of a large vessel, anterior circulation occlusion for enrollment. In addition, they were characterized by fast time-to-treatment. To achieve results in real-world settings similar to those in the clinical trials, treatment times, clinical protocols, and patient selection criteria should be similar to those in the RCTs. The evidence is sufficient to determine quantitatively that the technology results in a large improvement in the net health outcome; therefore, it is considered medically necessary.

The evidence for the use of endovascular mechanical embolectomy in individuals who have acute ischemic stroke due to basilar artery occlusion includes 1 nonrandomized comparative study and a number of case series. Relevant outcomes are overall survival, morbid events, functional outcomes, and treatment-related mortality and morbidity. These studies indicate that high rates of recanalization can be achieved with mechanical thrombectomy. However, additional comparative studies are needed to demonstrate that mechanical thrombectomy is superior to standard therapy. The evidence is insufficient to determine the effects of the technology on health outcomes. As a result, endovascular procedures with or without stenting are considered experimental, investigational and/or unproven for the elective treatment of symptomatic intracranial stenosis.

The evidence for the use of intracranial percutaneous transluminal angioplasty with or without stenting in individuals who have symptomatic intracranial stenosis includes 2 RCTs and a number of nonrandomized comparative studies and case series. Relevant outcomes are overall survival, symptoms, morbid events, functional outcomes, and treatment-related mortality and morbidity. Both available RCTs demonstrated no significant benefit with endovascular therapy. In particular, the SAMMPRIS trial was stopped early due to harms, because the rate of stroke or death at 30 days’ posttreatment was higher in the endovascular arm, which received percutaneous angioplasty with stenting. Follow-up of SAMMPRIS subjects has demonstrated no long-term benefit from endovascular therapy. Although some nonrandomized studies have suggested a benefit from endovascular therapy, the available evidence from 2 RCTs does not suggest that intracranial percutaneous transluminal angioplasty with or without stenting improves outcomes for individuals with symptomatic intracranial stenosis. The evidence is sufficient to determine qualitatively that the technology is unlikely to improve the net health outcome. As a result, intracranial percutaneous transluminal angioplasty with or without stenting are considered experimental, investigational and/or unproven for those with symptomatic intracranial stenosis.

The evidence for the use of endovascular coiling with intracranial stent placement or intracranial placement of a flow-diverting stent in individuals who have intracranial aneurysms when surgery is not appropriate and/or standard treatment does not permit aneurysm isolation includes several nonrandomized comparative studies and multiple single-arm studies. Relevant outcomes are overall survival, morbid events, functional outcomes, and treatment-related mortality and morbidity. The available nonrandomized comparative studies report occlusion rates for stent-assisted coiling that are similar to or higher than coiling alone and recurrence rates that may be lower than for coiling alone. For stent-assisted coiling with self-expanding stents, some evidence also shows that adverse event rates are relatively high, and 1 nonrandomized comparative trial reported that mortality is higher with stent-assisted coiling than with coiling alone. For placement of flow-diverting stents, 1 nonrandomized study comparing the flow-diverting stents to endovascular coiling for intracranial aneurysms demonstrated higher rates of aneurysm obliteration in those treated with the Pipeline endovascular device than those treated with coiling, with similar rates of good clinical outcomes. Results of clinical vetting completed by BCBSA indicated strong support for treatment of aneurysms that are not amenable to surgery or simple coiling. As a result, use of stent-assisted coiling with traditional stents for the treatment of intracranial aneurysms may be considered medically necessary when surgical treatment is not appropriate and standard endovascular techniques do not allow for complete isolation of the aneurysm. Overall, the available evidence is suggestive of a good efficacy and safety profile for endovascular therapies. Results of vetting indicated strong support for the use of flow-diverting stents for certain types of aneurysms; thus, flow-diverting stents may be considered medically necessary for the treatment of intracranial aneurysms when surgical treatment is not appropriate and the aneurysms meet anatomic criteria.

Contract:

Each benefit plan, summary plan description or contract defines which services are covered, which services are excluded, and which services are subject to dollar caps or other limitations, conditions or exclusions. Members and their providers have the responsibility for consulting the member's benefit plan, summary plan description or contract to determine if there are any exclusions or other benefit limitations applicable to this service or supply. If there is a discrepancy between a Medical Policy and a member's benefit plan, summary plan description or contract, the benefit plan, summary plan description or contract will govern.

Coding:

There are no specific procedure codes for intracranial angioplasty and stent placement.

If occlusion of a vascular malformation is performed as part of the treatment of an aneurysm, CPT code 61624 may be used.

For endovascular interventions for acute stroke, the components of the procedure are reported separately.

CODING:

Disclaimer for coding information on Medical Policies

Procedure and diagnosis codes on Medical Policy documents are included only as a general reference tool for each policy. They may not be all-inclusive.

The presence or absence of procedure, service, supply, device or diagnosis codes in a Medical Policy document has no relevance for determination of benefit coverage for members or reimbursement for providers. Only the written coverage position in a medical policy should be used for such determinations.

Benefit coverage determinations based on written Medical Policy coverage positions must include review of the member’s benefit contract or Summary Plan Description (SPD) for defined coverage vs. non-coverage, benefit exclusions, and benefit limitations such as dollar or duration caps.

CPT/HCPCS/ICD-9/ICD-10 Codes

The following codes may be applicable to this Medical policy and may not be all inclusive.

CPT Codes

61624, 61630, 61635, 61645, 61650, 61651, 75894

HCPCS Codes

C2623

ICD-9 Diagnosis Codes

Refer to the ICD-9-CM manual

ICD-9 Procedure Codes

Refer to the ICD-9-CM manual

ICD-10 Diagnosis Codes

Refer to the ICD-10-CM manual

ICD-10 Procedure Codes

Refer to the ICD-10-CM manual


Medicare Coverage:

The information contained in this section is for informational purposes only. HCSC makes no representation as to the accuracy of this information. It is not to be used for claims adjudication for HCSC Plans.

The Centers for Medicare and Medicaid Services (CMS) does have a national Medicare coverage position.

A national coverage position for Medicare may have been changed since this medical policy document was written. See Medicare's National Coverage at <http://www.cms.hhs.gov>.

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Policy History:

Date Reason
4/15/2018 Document reviewed. Coverage unchanged.
7/15/2017 Reviewed. No changes.
12/15/2016 Document updated with literature review. Coverage unchanged. The following was added to the Coverage section for informational purposes: NOTE 3: These policy statements are not intended to address the use of rescue endovascular therapies, including intra-arterial vasodilator infusion and intracranial percutaneous transluminal angiography, in delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage. The following was added to Description: The FDA approval of Trevo® ProVue and XP ProVue Retrievers as Class II devices, for patients experiencing ischemic stroke within 6 hours of symptom onset and following the administration of IV-tPA within 3 hours of symptom onset.
9/15/2016 Reviewed. No changes.
1/15/2016 Document updated with literature review. The following was changed in coverage for Acute Ischemic Stroke: 1) Endovascular mechanical embolectomy using a retrievable stent (e.g., Merci® Retriever, Penumbra System®, Solitaire™ Flow Restoration Device) or the Trevo® Retriever may be considered medically necessary in the treatment of acute ischemic stroke in patients with occlusion of the anterior circulation (e.g., middle cerebral artery or internal carotid artery) confirmed by a radiological image and a National Institute of Health Stroke Score (NIHSS) greater than or equal to 2; and 2) Endovascular interventions, such as intra-arterial mechanical embolectomy, thrombectomy, angioplasty or non-retrievable stenting, are considered experimental, investigational and/or unproven when the above criteria are not met. The following was added to coverage for Cerebral Aneurysms: Intracranial flow diverting stents with U.S. Food and Drug Administration (FDA) approval for the treatment of intracranial aneurysms may be considered medically necessary as part of the endovascular treatment of intracranial aneurysms that are not amenable to surgical treatment or standard endovascular therapy AND meet the following anatomic criteria: Large or giant wide-necked intracranial aneurysms, with a size of 10 mm or more and a neck diameter of 4 mm or more, in the internal carotid artery from the petrous to the superior hypophyseal segments.
10/15/2014 Document updated with literature review. The following was added: Endovascular interventions (mechanical embolectomy, angioplasty, stenting) are considered experimental, investigational and/or unproven in the treatment of acute stroke. For all other indications, coverage remains unchanged. Title was changed from: Intracranial Stenting or Angioplasty. Rationale and Description substantially revised. CPT/HCPCS code(s) updated.
9/15/2012 New medical document. Intracranial stent placement may be considered medically necessary when specific criteria are met; otherwise intracranial stent placement is considered experimental, investigational and unproven. Intracranial percutaneous transluminal angioplasty, with or without stenting, is considered experimental, investigational and unproven. (Coverage changed for stenting, but unchanged for angioplasty. This topic was previously addressed on MED202.032 Stenting for Vascular Occlusive Disease.)

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