Strong evidence for the efficacy of mechanical thrombectomy for acute stroke revealed at the International

Three randomized controlled trials, ESCAPE, EXTEND-IA, and SWIFT PRIME, presented today at the International Stroke Conference in Nashville, TN demonstrate that for acute ischemic stroke caused by large vessel occlusions, mechanical thrombectomy plus IV thrombolysis improves functional outcomes compared with IV-tPA alone. ESCAPE and EXTEND-IA were published online in the New England Journal of Medicine. SWIFT PRIME has not yet been published but was presented in abstract format. 

All 3 trials were stopped early in December 2014 after independent reviews by the individual data safety monitoring boards of each trial following the results of the MR CLEAN trial, which found that the addition of endovascular therapy improved functional outcomes when compared to treatment with IV tPA alone. Collectively, these 4 trials refute the much criticized negative results of the IMS III, MR RESCUE, and SYNTHESIS Expansion trials published in February 2013. These trials represent true landmark trials for our field and should be known to all members interested in the treatment of acute stroke. They also demonstrate the tenacity of the primary investigators of each trial in light of the disappointing results 2 years ago. 

Some details about each trial:

EXTEND-IA enrolled 70 patients at 14 centers in Australia and New Zealand who all had evidence of occlusion of the internal carotid or middle cerebral artery, evidence of salvageable brain tissue, and an ischemic core infarct volume of less than 70 mL on CT perfusion imaging.  The patients received IV tPA within 4.5 hours of stroke symptom onset before being randomized to mechanical thrombectomy within 6 hours of symptom onset.  The investigators’ results showed that the addition of endovascular therapy doubled patients’ rate of return to functional independence compared to treatment with IV-tPA alone.

Similarly, ESCAPE assessed 316 patients who were enrolled at 22 centers in Canada, the United States, Europe, and South Korea.  These patients had evidence of proximal vessel occlusion, a small infarct core, and moderate-to-good collateral circulation. They were randomized to IV-tPA or IV-tPA plus endovascular treatment with 86% of the endovascular treatment patients receiving treatment with a stent retriever.  The investigators’ reported that the addition of endovascular therapy doubled patients’ rate of return to functional independence and cut the risk of death from stroke in half compared to traditional treatment with IV-tPA alone.

The SWIFT PRIME trial was also presented but has not yet been published.  It included 196 patients enrolled at 39 US and European centers who had occlusions in the middle cerebral artery, or the carotid terminus confirmed by CT or MR angiography.  Similar to the other studies, these patients were eligible for IV tPA within 4.5 hours and for mechanical thrombectomy within 6 hours of stroke symptom onset. The study showed a statistically significant improvement in 90 day functional outcome for patients receiving endovascular therapy vs. TPA alone.

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