The merci retrieval system for acute stroke
The Merci Retrieval System® was cleared for use in patients with stroke in August 2004. However, there are few published results of “real world experience” with the device.
We captured single-center data on 25 consecutive patients with acute ischemic stroke treated with the Merci Retrieval System according to the MERCI trial except that we treated some patients with tandem proximal carotid and intracranial lesions with carotid angioplasty and stenting and some patients were treated within the 3-hour window.
Median patient age was 63 years and median initial National Institute of Health Stroke Scale (NIHSS) score was 18. Isolated M1 or M2 middle cerebral artery lesions occurred in 52% “carotid T” lesions in 8%, and vertebrobasilar lesions in 8% Tandem lesions involving proximal carotid and proximal intracranial vessel occurred in 32%, necessitating emergent multilevel treatment including carotid stenting. Median duration from symptom onset to Merci device utilization was 5.2 hours. Successful reperfusion (≥thrombolysis in myocardial infarction [TIMI] 2 flow) in the target vessel was obtained in 56% of cases. Statistical analysis revealed a strong correlation between ability to achieve greater than or equal to TIMI 2 flow a good clinical outcome as measured by 3-month NIHSS score, modified Rankin Scale (mRS), and mortality (nine out of the 12 without successful reperfusion died compared to none of the 13 with ≥TIMI 2 flow, p<0.001). Younger age and lower NIHSS score on presentation were also predictors of good clinical outcome at 3 months.
These “real world data” demonstrate that the results of the previous MERCI trial can be “independently replicated” at a regional stroke center. Although the results of placebo-controlled trials are still pending, mechanical revascularization has become a critical component of our acute stroke protocol, particularly for severe strokes. Issues still remain regarding recalcitrant lesions and operator experience, which necessitate further clinical testing and device optimization.