Mechanical thrombectomy: Stent retrievers vs. aspiration catheters

Mechanical thrombectomy, in conjunction with systemic thrombolysis, is currently the standard of care for the treatment of acute ischemic stroke. Mechanical thrombectomy extends the therapeutic window up to at least 8 hours from the time of symptom onset and is more efficient than systemic thrombolytic agents in removing clots resistant to enzymatic degradation. It is also a viable option for patients with various contraindications against the use of systemic thrombolysis. Treatment of patients with acute ischemic strokes using mechanical thrombectomy devices has yielded both higher rates of revascularization as well as superior clinical outcomes when compared with medical therapy with intravenous thrombolytics alone. The use of first-generation thrombectomy devices, most notably the Merci Retriever system (Stryker, Kalamazoo, MI, USA) and the Penumbra Aspiration device (Penumbra Inc., Alameda, CA, USA), achieved high rates of revascularization of occluded large cerebral vessels but did not necessarily result in high rates of favorable clinical outcomes. Second-generation devices, known as stent retrievers, were therefore created with the goal of achieving faster revascularization of occluded vessels and improved rates of favorable clinical outcomes. Stent retrievers, most notably the Solitaire (ev3/Covidien, Irvine, CA, USA) and the Trevo (Stryker), were shown to be superior to first-generation devices in terms of achieving higher rates of favorable clinical outcomes. Aspiration combined with stent retrievers or alone has also shown great promise. Moreover, several recent randomized control trials have demonstrated the superiority of medical therapy with mechanical thrombectomy using stent retrievers over medical therapy alone in achieving good clinical outcome in acute stroke patients. These clinical trials also demonstrated the relative safety of mechanical thrombectomy with stent retrievers compared to the safety of best medical therapy.