New Drugs and Technologies Current Status of Endovascular Stroke Treatment

Stroke is the third-leading cause of death in the United States, Canada, Europe, and Japan. According to American Heart Association statistics, there are now 795 000 new strokes each year, resulting in 200 000 deaths, or 1 of every 16 deaths, per year in the United States.1 Ischemic stroke represents 80% of the total, and hemorrhagic stroke makes up the remainder. Stroke is the leading cause of adult disability in both North America and Medicare reimbursement for long-term adult care. The National Institutes of Health (NIH) estimate that stroke costs exceed $73 billion in US healthcare dollars per year.1 Improved treatments are needed to reduce the burden of human suffering and to lessen the financial burden on society. Epidemiologically, there are 795 000 strokes per year in the United States,1 but this number does not represent the number of treatable strokes. The real number of ischemic strokes amenable to some form of endovascular revascularization intervention is probably a small subset of the total number. This disparity explains, at least in part, the relatively slow progress in stroke trial enrollment and scientific progress compared with the more rapid development of cardiac interventions. The number of acute strokes potentially requiring emergent intervention ranges from 58 000 to 120 000 per year, or 7% to 15% of the total number, because many acute ischemic strokes are due to hemorrhage, small-vessel occlusions (lacunar strokes), transient ischemic attacks, end-of-life strokes, and mild strokes that do not warrant the risk of an endovascular procedure.2 In most communities, only 1% to 7% of stroke victims arrive at hospital in time for stroke revascularization therapies. Even in communities with highly organized and active stroke programs, 10% of stroke victims receive immediate treatment.3 Even if such programs were instituted across the United States, 58 000 stroke victims (9% of 645 000 ischemic stroke patients) would receive treatment.2 The number potentially needing an endovascular intervention is less clear. Extensive brain injury is already present in many patients on admission. In comprehensive stroke centers following evidence-based guidelines for intervention, endovascular ischemic stroke procedures remain among the least common procedures that neurointerventionalists perform (on average, 8 procedures per year).4 The reason is that 20% of strokes are due to small-artery occlusions (lacunar strokes), and another 20% to large-artery occlusions causing severe strokes. We have organized this review as follows. First, we discuss stroke imaging, because it emphasizes the essential problem in distinguishing ischemic penumbra, which is potentially recoverable cerebrum, from infarcted cerebrum, which is not recoverable. Second, we review intravascular fibrinolytic therapies, intravenous and intra-arterial fibrinolysis. Third, we describe mechanical revascularization therapies, including thromboembolectomy, suction thrombectomy, angioplasty and stent revascularization, and the new stentretriever thrombectomy. Finally, we discuss the potential futility of some of these therapies without further scientific advancements.