Retrievable stents, "stentrievers," for endovascular acute ischemic stroke therapy

Endovascular therapy for acute ischemic stroke continues to evolve to improve both efficacy and safety. In the late 1990s, intra-arterial chemical thrombolysis with prourokinase was shown to be effective in achieving partial recanalization and improving clinical outcome, in comparison with intra-arterial heparin administration. However, this was at the expense of an increase in the rate of symptomatic intracranial hemorrhage to 10%. To improve the rate of recanalization, expand the time window, and reduce the risk of symptomatic intracranial hemorrhage, mechanical thrombectomy was introduced, with initial approval of the Merci clot retriever, a corkscrew-like device, and then more recently with approval of the Penumbra thromboaspiration system. Both devices are associated with a high rate of recanalization (total, partial, and complete). However, time to recanalization was on average 45 minutes, with a low rate of complete clot resolution, given that the majority of patients achieved only partial recanalization. More recently, retrievable stents have shown promise in reducing the time to recanalization, and they achieve a higher rate of complete clot resolution with improved feasibility. The retrievable stent can be opened within the clot to engage it within the stent struts, and subsequently it is retrieved by pulling it under flow arrest. The retrievable stents provide a new tool in the armamentarium of devices that can be used to achieve safe and timely clot removal. This review provides the historical evolution of endovascular therapy to use of stentreivers.