Acute Ischemic Stroke: Discussion

Abstract

Stroke is the leading cause of disability in adults in North America [1]. In the last 20 years, interest has soared in search of a reperfusion therapy for ischemic stroke caused by vessel occlusion. The revolutionary trial by the National Institute of Neurologic Disorders and Stroke (NINDS) showed that intravenous thrombolysis could be achieved with an intravenous tissue plasminogen activator (tPA). The effectiveness of tPA is time-dependent, and benefit has been shown up to 4.5 h after the onset of stroke. Although tPA can be initiated quickly after a new ischemic stroke is suspected, the short treatment window excludes many patients from therapy. There are also other risks such as development of asymptomatic and symptomatic intracranial hemorrhage (ICH) as well as failure of therapy [2, 3]. These limitations in IV tPA therapy have led to the development of procedural-based interventions such as intra-arterial thrombolytics and mechanical thrombectomy. In 2013, utilization of endovascular therapy was called into question by three randomized controlled trials, showing no benefit of endovascular treatment of stroke compared to standard care or IV tPA [4–6]. These trials used first-generation devices and intra-arterial chemical thrombolysis as the mainstay of treatment. Recruitment was also not limited to patients with a radiographic documentation of proximal large vessel occlusion. Despite different trial methods and designs, none showed benefit of endovascular therapy compared to less invasive measures (although no harm was shown). As these trial results were published, three other multicenter RCTs were enrolling patients to compare endovascular treatment to standard care in managing acute ischemic stroke. The trials ESCAPE, MR CLEAN, and EXTEND-IA all concluded that endovascular treatment of acute vessel occlusion in the anterior circulation was superior to medical management with IV tPA alone [7–9]. These new trials utilized the recent technology of stent retrievers. They also required radiographic evidence of proximal vessel occlusion and noninvasive imaging to assess tissue viability. Despite their differences in trial design, these recent trials all showed a benefit to patients with acute ischemic stroke caused by proximal vessel occlusion from endovascular therapy. In this chapter, we will give a brief history of endovascular therapy for stroke, including the changes in technology, and discuss the three primary equivocal studies for stroke intervention as compared to the three recent studies, which favor endovascular therapy for the treatment of acute ischemic stroke.