Surgery Section - Mechanical Embolectomy for Treatment of Acute Stroke

IMPORTANT REMINDER

This Medical Policy has been developed through consideration of medical necessity, generally accepted standards of medical practice, and review of medical literature and government approval status.

Benefit determinations should be based in all cases on the applicable contract language. To the extent there are any conflicts between these guidelines and the contract language, the contract language will control.

The purpose of medical policy is to provide a guide to coverage. Medical Policy is not intended to dictate to providers how to practice medicine. Providers are expected to exercise their medical judgment in providing the most appropriate care.

DESCRIPTION

Over 750,000 strokes occur annually in the United States. Some strokes are caused by emboli and these frequently present as acute neurologic emergencies. Tissue plasminogen activator (tPA) given intravenously within 3 hours of symptom onset is FDA approved for treatment of acute ischemic strokes. Mechanical embolectomy is being studied as a method of stroke treatment.

The Merci Retriever was cleared by the FDA in August 2004 through the 510(k) process. This device was judged equivalent to a predicate device, the Concentric Retriever. The FDA clearance indicated that the MERCI Clinical Study established that no new issues of safety and effectiveness exist when the Merci Retriever is used for thrombus removal versus foreign body removal from the neurovasculature.  Several modified Merci Retrievers, also manufactured by Concentric Medical, Inc, received 510(k) clearance from the FDA in February 2009. (2) The clearance notes that the Modified Merci Retrievers are intended to restore blood flow in the neurovasculature by removing thrombus in patients experiencing ischemic stroke. Patients who are ineligible for intravenous tPA or who fail intravenous tPA therapy are candidates for treatment. The device also has clearance for retrieval of foreign bodies misplaced during interventional radiological procedures in the neuro, peripheral, and coronary vasculature.

POLICY/CRITERIA

Mechanical embolectomy is considered investigational in the treatment of acute stroke.

POSITION STATEMENT

Support for use of the Merci Retrieval System comes from the MERCI (Mechanical Embolus Removal in Cerebral Ischemia) trial. (3) This was a multicenter (25 centers) prospective non-randomized trial of this device for patients with symptoms of acute stroke for less than 8 hours who were not candidates for thrombolytic therapy, either because of contraindications (~25%) or because symptoms were present for more than 3 hours. One thousand eight hundred nine (1,809) patients were screened to identify the 151 patients eligible to be enrolled in the trial. Chief reasons for exclusions were NIHSS (NIH Stroke Score) too low or improving, intracranial hemorrhage, or inability to obtain consent. Of the 151 patients, 141 had the device deployed. Recanalization was achieved in 46% (69/151) of patients on an intent to treat analysis and in 48% (68/141) of patients in whom the device was employed. (One patient had “spontaneous” recanalization.) The status of vessels distal to the treatable vessel was not considered in the recanalization rate. Clinically significant procedural complications occurred in 10 patients (7.1%) and symptomatic intracranial hemorrhages were observed in 11 (7.8%). Good neurological outcomes were more frequent at 90 days in those with successful recanalization compared to those with unsuccessful recanalization (46% vs. 10%, p<0.0001) and mortality was less (32% vs. 54%, p=0.01). Of note, in the study up to six passes could be made to remove the clot and at least 2 devices were used in each patient in the MERCI trial. The MERCI investigators compared their patients to the placebo arm of the PROACT II (Pro-lyse in Acute Cerebral Thromboembolism II (4) study to determine safety and efficacy of mechanical embolectomy.

To determine if this treatment improves net outcomes (considers both benefits and risk) in stroke, there must be a comparison with an appropriate control group. It is not clear what the recanalization rate would have been without embolectomy in those patients who had successful clot removal. Concurrent control groups are also important to evaluate possible unexpected events when intravascular devices are used that may damage arterial endothelium.3

Concerns have been raised about using the patients from the PROACT II study as historic controls. These concerns include the fact that the MERCI trial included patients with different types of occlusions; PROACT II had M1 and M2 occlusions while the MERCI trial also included internal carotid and vertebral basilar systems.(5) Questions have also been raised about the outcome measure of recanalization since the MERCI study did not look for distal emboli. Also, there are concerns about the reliability of the TIMI perfusion score as reported in this trial and thus questions about whether the recanalization rates can be compared among studies. (6)

An ongoing trial, the MR RESCUE study (Magnetic Resonance and Recanalization of Stroke Clots Using Embolectomy) being sponsored through the National Institutes of Neurological Disorders and Stroke, is underway. This study randomizes patients with stroke seen within eight hours to either medical therapy or embolectomy. Thus trial should provide important comparative data.(7)+

The available published data are not sufficient to determine whether this approach improves health outcomes. An updated search of the MEDLINE database through August 14, 2009 failed to return any new clinical trial data that alter the conclusions reached above. Reports continue to be from single center studies with no control group for comparison. Given the lack of controlled studies to assess the impact of this treatment on outcome, the effectiveness of mechanical embolectomy for the management of acute stroke remains uncertain.(8-13)

Position Statements

REFERENCES

1. BlueCross and BlueShield Association Medical Policy Reference Manual, Policy No. 2.01.76
2. U.S. Food and Drug Administration (FDA) http://www.accessdata.fda.gov/cdrh_docs/pdf9/K090085.pdf (Verified 8/17/09)
3. Smith WS, Sung G, Starkman S et al. Safety and efficacy of mechanical embolectomy in acute ischemic stroke: Results of the MERCI trial. Stroke 2005;36(7):1432-8
4. Furlan A, Higashida R, Wechsler L et al. Intra-arterial prourokinase for acute ischemic stroke. The PROACT II study: a randomized controlled trial. JAMA 1999;282(21):2003-11
5. Becker KJ, Brott TG. Approval of the MERCI clot retriever: a critical view. Stroke 2005;36(2):400-3
6. Tomsick TA. Mechanical embolus removal: a new day dawning. Stroke 2005;36(7):1439-40
7. http://www.clinicaltrials.gov/ct2/show/NCT00389467?term=MR+rescue& rank=1%20 (Verified 08/17/09)
8. Kim D, Jahan R, Starkman S et al. Endovascular mechanical clot retrieval in a broad ischemic stroke cohort. Am J Neuroradiol 2006;27(10):2048-52
9. Devlin TG, Baxter BW, Feintuch TA et al. The Merci Retrieval System for acute stroke: the Southeast Regional Stroke Center experience. Neurocrit Care. 2007;6(1):11-21
10. Flint AC, Duckwiler GR, Budzik RF et al. Mechanical thrombectomy of intracranial internal carotid occlusion: pooled results of the MERCI and Multi MERCI Part I trials. Stroke. 2007 Apr;38(4):1274-80
11. Gonzalez A, Mayol A, Martinez E, et al. Mechanical thrombectomy with snare in patients with acute ischemic stroke. Neuroradiology 2007;49(4):365-72
12. Smith WS, Sung G, Saver J et al. Mechanical thrombectomy for acute ischemic stroke: final results of the Multi MERCI trial. Stroke 2008; 39(4):1205-12
13. Bose A, Henkes H, Alfke K et al. The Penumbra System: a mechanical device for the treatment of acute stroke due to thromboembolism. AJNR Am J Neuroradiol 2008; 29(7):1409-13
14. Adams HP, delZoppo G, Alberts MJ et al. Guidelines for the early management of adults with ischemic stroke: a guideline from the American Heart Association/American Stroke Association Stroke Council, Clinical Cardiology Council, Cardiovascular Radiology and Intervention Council, and the Atherosclerotic Peripheral Vascular Disease and Quality of Care Outcomes in Research Interdisciplinary Working Groups: The American Academy of Neurology affirms the value of this guideline as an educational tool for neurologists. Circulation 2007; 115(20):e478-534

CROSS REFERENCES

None

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