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Multi MERCI

Mechanical Thrombectomy for Acute Ischemic Stroke: Final Results of the Multi MERCI Trial

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Year of Publication: 2008

Authors: Wade S. Smith, MD, PhD; Gene Sung, ..., MD; for the Multi MERCI Investigators

Journal: Stroke

Citation: Stroke. 2008;39:1205-1212.

Link: https://www.ahajournals.org/doi/pdf/10.1...EAHA.107.497115

PDF: https://www.ahajournals.org/doi/pdf/10.1...EAHA.107.497115

Clinical Question

To evaluate if a newer generation mechanical thrombectomy device (L5 Retriever) could improve recanalization rates and to assess the safety of mechanical thrombectomy in patients with acute large vessel occlusion stroke within 8 hours of onset, including those who had persistent occlusion after receiving intravenous tPA.

Study Overview

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

The newer L5 Retriever achieved a 57.3% recanalization rate alone, and recanalization rate with all methods was 68%.
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.

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 in patients with large vessel occlusion stroke treated within 8 hours of symptom onset; 177 patients were enrolled and the device was deployed in 164, who formed the analyzed cohort.
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%.

      

Design

Study Type: International, multicenter, prospective, single-arm trial

Randomization:

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).

Enrollment Period: January 2004 to July 2006

Follow-up Duration: 90 days

Centers: 15

Countries: United States, Canada

Sample Size: 164

Analysis: 177 patients were enrolled; the device was deployed in 164 patients, who form the analyzed cohort for all results. The primary outcome was the L5 Retriever postdevice recanalization rate, tested for noninferiority against a prespecified performance goal of ≥44%. Secondary outcomes compared recanalized vs. non-recanalized patients using Fisher exact test.

Inclusion Criteria

Age ≥18 years
National Institutes of Health Stroke Scale (NIHSS) score ≥8
Stroke symptom onset within 8 hours
Angiographically confirmed occlusion of a treatable large vessel (ICA, M1, M2, vertebral, or basilar artery)
Included patients who had persistent occlusion after receiving IV tPA

Exclusion Criteria

Inability to obtain informed consent
Current pregnancy
Serum glucose <50 mg/dL
Excessive tortuosity of cervical vessels precluding device delivery/deployment
Known hemorrhagic diathesis
Known coagulation factor deficiency
Oral anticoagulation with international normalized ratio (INR) >3.0
Use of heparin within 48 hours with prothrombin time >2× normal
Platelet count <30,000/μL
History of severe allergy to contrast media
Sustained systolic blood pressure >185 mm Hg or diastolic >110 mm Hg despite treatment
CT scan revealing significant mass effect with midline shift
Greater than 50% stenosis of the artery proximal to the target vessel
Life expectancy <3 months

Baseline Characteristics

Characteristic	Control	Active
Group		Overall Population (n=164)
Age, mean±SD, years		68.1±16.0
Female, %		57
Baseline NIHSS, median (interquartile range)		19 (15-23)
IV tPA pretreatment, %		29
Site of occlusion - Middle cerebral artery, %		60
Symptom onset to groin puncture, median hours (IQR)		4.3 (3.2-5.3)

Arms

Field	Mechanical Thrombectomy
Intervention	Mechanical thrombectomy using a Merci Retriever device (X5, X6, or L5). Adjunctive intra-arterial tPA was permitted if device-only thrombectomy failed.
Duration	Single procedure

Outcomes

Outcome	Type	Control	Intervention	HR / OR / RR	P-value
Successful recanalization (TIMI grade II or III flow) of the target vessel after treatment with the L5 Retriever device alone.	Primary		57.3% (75/131)		Threshold met — recanalization exceeded prespecified performance goal of ≥44% (noninferiority to X5/X6); no P value reported
Favorable outcome (mRS ≤2) at 90 days	Secondary	9.6% (Not Recanalized)	49% (Recanalized)	RR 5.1 (95% CI, 2.2-12)	<0.001
Mortality at 90 days	Secondary	52% (Not Recanalized)	25% (Recanalized)	RR 0.48 (95% CI, 0.31-0.73)	<0.001
Overall final recanalization rate (all devices and adjunctive therapies)	Secondary		68% (95% CI, 61-75)
Procedural complications (overall)	Adverse		9.8% (95% CI, 5.2-14.3)
Clinically significant procedural complications	Adverse		5.5% (95% CI, 2.0-9.0) [9/164]
Symptomatic intracranial hemorrhage	Adverse		9.8% (95% CI, 5.2-14.3) [16/164]
Symptomatic PH-2 hemorrhage	Adverse		2.4% (95% CI, 0.1-4.8) [4/164]
Asymptomatic hemorrhage	Adverse		30.5% of all patients
Device-related serious adverse events	Adverse		2.4% (95% CI, 0.1-4.8)

Subgroup Analysis

There were no significant differences in rates of intracranial hemorrhage or procedural complications between patients who received prior IV tPA and those who did not.

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.

Funding

Concentric Medical, Inc.

Based on: Multi MERCI (Stroke, 2008)