Merci mechanical thrombectomy retriever for acute ischemic stroke therapy: literature review

Mechanical thrombectomy is a promising adjuvant or stand-alone therapy for acute ischemic stroke (AIS) caused by occlusion of a large vessel in patients beyond the systemic thrombolysis therapeutic window. This review focuses on the clinical and angiographic outcomes of mechanical thrombectomy with use of the Merci retriever device.

Available literature published to date on the major trials and observational studies involving the Merci retriever was reviewed. In addition to the review, results from studies involving the Merci retriever were compared to results from Prolyse in Acute Cerebral Thromboembolism II (PROACT II) and the Penumbra device studies. The predictors for favorable outcome following revascularization with the Merci device were reviewed on the basis of published stratified analyses. Favorable clinical outcome was defined in the Merci experience by a modified Rankin Scale (mRS) score of ≤ 2 at 90 days following AIS.

Presented in this review are a total of 1,226 patients treated with the Merci device; 305 patients are from 2 pivotal trials involving the device, and the remaining 921 patients are from observational studies in the Merci registry. The 90-day mRS of ≤ 2 was achieved in 32% of the patient group, with an overall mortality rate of 35.2%. Symptomatic intracerebral hemorrhage was identified in 7.3% of patients treated with Merci retriever, a result comparable to that in the PROACT II and Penumbra thrombectomy trials. Successful recanalization, lower NIH Stroke Scale score, and younger age were identified as the strongest predictors of favorable outcomes.

Mechanical thrombectomy with the Merci retriever device is a safe treatment modality for AIS patients presenting with a large-vessel occlusion within 8 hours of symptom onset. Although the Merci retriever showed a good recanalization rate, there are currently no randomized clinical trials to assess its clinical efficacy in comparison with systemic thrombolysis within a window of 3 to 4.5 hours or with standard of care beyond a 4.5-hour window.