PDF: Multi MERCI
(2008)Objective
To evaluate the performance of a newer generation thrombectomy device (L5 Retriever) and the safety of combining IV tPA with mechanical thrombectomy for large vessel stroke within 8 hours of onset.
Study Summary
• Successful recanalization was strongly associated with good outcomes (49% vs 9.6% with mRS 0-2) and lower mortality (25% vs 52%).
• Symptomatic ICH occurred in 9.8% of all patients.
Intervention
Mechanical thrombectomy using Merci devices (primarily the newer L5 Retriever) within 8 hours of stroke onset. A subset of patients (29%) had received IV tPA prior to the procedure. Follow-up was 90 days.
Study Design
Arms: Array
Outcome
• Good clinical outcome (mRS 0-2 at 90 days) was achieved in 49% of recanalized patients vs. 9.6% of non-recanalized patients (p<0.001).
• 90-day mortality was 25% in recanalized patients vs. 52% in non-recanalized patients (p<0.001).
• Symptomatic intracranial hemorrhage rate was 9.8%; clinically significant procedural complications occurred in 5.5%.
Bottom Line
The newer generation L5 Retriever was associated with numerically higher rates of recanalization compared to first-generation devices, although the difference was not statistically significant. Successful vascular recanalization, by any method, was strongly associated with improved functional outcomes and lower mortality at 90 days. Performing thrombectomy after IV tPA did not increase complications.
Major Points
- Multi MERCI was a prospective, single-arm, international, multicenter trial that enrolled 164 patients with large vessel occlusion stroke who were treated within 8 hours of symptom onset.
- The study included a cohort of patients (29%) who had persistent vessel occlusions after treatment with IV tissue plasminogen activator (tPA).
- The newer L5 Retriever device achieved successful recanalization (TIMI II or III flow) in 57.3% of cases. The overall final recanalization rate after all interventions (including adjunctive intra-arterial tPA) was 68%.
- A good clinical outcome (mRS 0-2) at 90 days was achieved in 36% of all patients, and was significantly more likely in patients with successful recanalization (49% vs. 9.6%; P<0.001).
- Mortality at 90 days was 34% overall, and was significantly lower in patients with successful recanalization (25% vs. 52%; P<0.001).
- The rate of symptomatic intracranial hemorrhage was 9.8%, and the rate of clinically significant procedural complications was 5.5%.
Study Design
- Study Type
- International, multicenter, prospective, single-arm trial
- Randomization
- No
- Blinding
- This was an open-label, single-arm study. Angiographic outcomes were determined by unblinded local investigators. A central core lab reviewed imaging for hemorrhages, which were adjudicated by an independent data safety monitoring board (DSMB).
- Sample Size
- 164
- Follow-up
- 90 days
- Centers
- 15
- Countries
- United States, Canada
Primary Outcome
Definition: Successful recanalization (TIMI grade II or III flow) of the target vessel after treatment with the L5 Retriever device alone.
| Control | Intervention | HR/OR | P-value |
|---|---|---|---|
| 57.3% (75/131) | - | Met prespecified non-inferiority goal of ≥44% |
Limitations & Criticisms
- The trial was a single-arm study without a contemporaneous control group, making it impossible to definitively conclude that thrombectomy improved outcomes over medical management alone.
- The angiographic outcomes (recanalization) were interpreted by unblinded site investigators rather than a blinded central core lab, which could introduce bias.
- The study enrolled a heterogeneous population with no upper limits on age or stroke severity, making direct mortality comparisons with other trials difficult.
Citation
Stroke. 2008;39:1205-1212.