What the SWIFT and TREVO II trials tell us about the role of endovascular therapy for acute stroke.

1 and the TREVO II trial, 2 published online in Lancet in August 2012, are important trials in the history of endovascular therapy for acute ischemic stroke for several reasons. First, both randomized trials compared a new technology , 2 versions of a stent-retriever, with a previously Food and Drug Administration-cleared technology, the Merci Retriever. The latest iteration of the Merci Retriever, which had been cleared for use since 2005, is a flexible nitinol wire with distal corkscrew-shaped coil loops with attached filaments. Stent-retriever technology is based on self-expanding stents that can be fully deployed and then retrieved about 5 minutes later, after migration of the thrombus through the stent struts. 3 Retrievable stents were introduced in 2010 in experienced, high-volume comprehensive European stroke centers with increased rates of recanalization in a shorter time compared with intra-arterial thrombolysis. 4 The Merci Retriever and retrievable stents are distal thrombectomy devices that require navigation of the device through and beyond the site of occlu-sion without image-guidance of a high-resolution biplane or 3D roadmap. In contrast, proximal thrombectomy devices allow a safe, image-guided approach to the site of occlusion and aspiration of the thrombus. These 2 randomized trials broke the trend of single-arm trials comparing a new technology with the intravenous hepa-rin arm of the randomized PROACT II trial study, which was completed in 1998. 5 The goal of past single-arm trials, used for both the Merci Retriever 6,7 and Penumbra Aspiration System, 8 was to obtain 510k clearance by the FDA, or regulatory approval in other countries, for thrombectomy in acute isch-emic stroke. However, no randomized trial of these devices has demonstrated improved clinical outcome by a thrombec-tomy device compared with standard therapy, whether intravenous tissue-type plasminogen activator (tPA) within 3 and subsequently 4.5 hours, or no reperfusion therapy >4.5 hours. Second, both trials demonstrated superiority with regards to the primary study end point compared with the Merci Retriever. The primary end point in the SWIFT trial was thrombolysis in myocardial ischemia scale 2 or 3 flow in all treatable vessels 9 without symptomatic intracranial hemorrhage after ≤3 passes of the assigned device, as assessed by an independent core laboratory that was masked to study assignment. The primary end point in the TREVO II trial was a thrombolysis in cerebral infarction scale 2 or 3 flow, 9 with the assigned device alone as assessed by an unmasked central imaging core. The use …