Safety and efficacy of mechanical embolectomy in acute ischemic stroke - Results of the MERCI trial

Background and Purpose - The only Food and Drug Administration (FDA)- approved treatment for acute ischemic stroke is tissue plasminogen activator (tPA) given intravenously within 3 hours of symptom onset. An alternative strategy for opening intracranial vessels during stroke is mechanical embolectomy, especially for patients ineligible for intravenous tPA. Methods - We investigated the safety and efficacy of a novel embolectomy device (Merci Retriever) to open occluded intracranial large vessels within 8 hours of the onset of stroke symptoms in a prospective, nonrandomized, multicenter trial. All patients were ineligible for intravenous tPA. Primary outcomes were recanalization and safety, and secondary outcomes were neurological outcome at 90 days in recanalized versus nonrecanalized patients. Results - Recanalization was achieved in 46 % (69/151) of patients on intention to treat analysis, and in 48 % (68/141) of patients in whom the device was deployed. This rate is significantly higher than that expected using an historical control of 18 % (P < 0.0001). Clinically significant procedural complications occurred in 10 of 141 (7.1 %) patients. Symptomatic intracranial hemorrhages was observed in 11 of 141 (7.8 %) patients. Good neurological outcomes ( modified Rankin score <= 2) were more frequent at 90 days in patients with successful recanalization compared with patients with unsuccessful recanalization (46 % versus 10 %; relative risk [RR], 4.4; 95 % CI, 2.1 to 9.3; P < 0.0001), and mortality was less (32 % versus 54 %; RR, 0.59; 95 % CI, 0.39 to 0.89; P = 0.01). Conclusions - A novel endovascular embolectomy device can significantly restore vascular patency during acute ischemic stroke within 8 hours of stroke symptom onset and provides an alternative intervention for patients who are otherwise ineligible for thrombolytics.