Thrombectomy or tPA for Acute Ischemic Stroke?

MedicalResearch.com Interview with:
Saleh A Almenawer, MD
Neurosurgeon, Hamilton Health Sciences
McMaster University
Hamilton, ON Canada 

Medical Research: What is the background for this study?

Dr. Almenawer: The current standard therapy for acute ischemic stroke is intravenous tissue plasminogen activator (tPA), which improves survival and functional outcomes when administered as early as possible after stroke. However, the use of intravenous tPA is limited by the narrow therapeutic time window (< 4.5 hours) and by important contraindications, including coagulopathy, recent surgery, or stroke or head injury within the past 3 months. This leaves as few as 10% of patients presenting with ischemic stroke eligible for treatment with tPA. Moreover, intravenous tPA is associated with long recanalization times and poor revascularization rates in proximal large vessel occlusion, and the prognosis of these patients remains poor. The limitations of intravenous tPA have spurred interest in endovascular thrombectomy for acute ischemic stroke, analogous to thrombolysis versus percutaneous coronary intervention for myocardial infarction. Several randomized clinical trials (RCTs) have compared clinical outcomes of mechanical thrombectomy to standard medical treatment with intravenous tPA. The current study was a meta-analysis of RCTs that aimed to answer the question of whether endovascular thrombectomy is associated with better clinical outcomes than intravenous tPA, and accordingly, whether endovascular thrombectomy should replace intravenous tPA as the new standard of care for ischemic stroke.

Medical Research: What are the main findings?

Dr. Almenawer: Our meta-analysis included 8 RCTs involving 2,423 patients, including 1,313 who underwent endovascular thrombectomy and 1,110 who received standard medical care with intravenous tPA. Functional outcome was assessed using the modified Rankin scale (mRS), a 7-score ordinal scale that ranges from 0 (no symptoms) to 6 (death), evaluated at 90 days after stroke. We found that endovascular thrombectomy resulted in better functional outcomes (lower mRS scores) than standard medical treatment. A greater proportion of patients who underwent mechanical thrombectomy achieved functional independence at 90 days (45%) than standard medical therapy (32%). This reflects a number needed to treat (to achieve functional independence) of 8. Furthermore, endovascular thrombectomy was associated with significantly higher rates of angiographic revascularization at 24 hours compared with standard medical care (76% versus 34%), but no difference in rates of symptomatic intracranial hemorrhage (5.7% versus 5.1%) or mortality (16% versus 18%). The positive treatment effect of endovascular thrombectomy over standard medical treatment was maximal when computed tomographic or magnetic resonance angiography was used to confirm large vessel occlusion prior to undertaking endovascular intervention, when mechanical thrombectomy was used in combination with intravenous tPA, and when stent retrievers were used for mechanical thrombectomy rather than older generation devices.

Medical Research: What should clinicians and patients take away from your report?

Dr. Almenawer: In our study, among patients with acute ischemic stroke, endovascular therapy with mechanical thrombectomy versus standard medical care with tPA was associated with improved functional outcomes and higher rates of angiographic revascularization, but no significant difference in symptomatic intracranial hemorrhage or all-cause mortality at 90 days. Ultimately then, in patients presenting with acute ischemic stroke secondary to proximal large vessel occlusion, endovascular thrombectomy within 6 hours of stroke onset should be considered the standard of care treatment. Ideally, the patient should undergo computed tomographic or magnetic resonance angiography to confirm large vessel occlusion prior to endovascular treatment, endovascular thrombectomy should be combined with intravenous tPA (where contraindications permit), and newer stent retriever devices should be used to perform mechanical thrombectomy.

Medical Research: What recommendations do you have for future research as a result of this study?

Dr. Almenawer: Future studies are needed to systematically further study the relationship of patient-, disease-, and treatment-related variables with outcomes following mechanical thrombectomy, and to identify the ideal patient to undergo endovascular therapy. Limits on age, ASPECTS, NIHSS score, and, perhaps most importantly, time to treatment, need to be explored. In addition to optimizing patient selection, trials should explore and define the optimal endovascular therapy with respect to technique, device, regional vs general anesthesia, and dosage of intraarterial thrombolytic, if any. The relationship of these variables to safety outcomes, such as mortality and morbidity, should also be further studied. The results of such studies could inform the development of clinical practice guidelines. Moreover, studies are needed to evaluate the cost-effectiveness of endovascular therapy for the treatment of ischemic stroke.

Citation:

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Saleh A Almenawer, MD (2015). Thrombectomy or tPA for Acute Ischemic Stroke? 

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