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MERCI

Safety and Efficacy of Mechanical Embolectomy in Acute Ischemic Stroke: Results of the MERCI Trial

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Year of Publication: 2005

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

Journal: Stroke

Citation: Stroke. 2005;36:1432-1440.

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 investigate the safety and efficacy of the Merci Retriever device for mechanical embolectomy to restore vascular patency in patients with acute ischemic stroke within 8 hours of symptom onset who are ineligible for intravenous tissue plasminogen activator (tPA).

Bottom Line

The Merci Retriever device successfully restores vascular patency in a significant proportion of acute ischemic stroke patients with large vessel occlusions who are ineligible for intravenous tPA. Successful recanalization is strongly associated with substantially improved neurological outcomes and reduced mortality at 90 days.

        Major Points
        The MERCI trial was a prospective, single-arm, multicenter study involving 151 patients with acute large vessel occlusion stroke presenting within 8 hours of onset who were ineligible for intravenous tPA.
The primary efficacy outcome, vessel recanalization (TIMI II or III flow), was achieved in 46% of patients on an intention-to-treat basis, which was significantly higher than the 18% historical control rate from the PROACT-II trial (P<0.0001).
Patients with successful recanalization had significantly better neurological outcomes (mRS ≤2) at 90 days compared to those without recanalization (46% vs. 10%, respectively; P<0.0001).
Mortality at 90 days was significantly lower in the recanalized group compared to the non-recanalized group (32% vs. 54%, respectively; P=0.01).
Clinically significant procedural complications occurred in 7.1% of patients, and symptomatic intracranial hemorrhage occurred in 7.8%.

      

Design

Study Type: Prospective, single-arm, multicenter trial

Randomization:

Blinding: This was a single-arm, open-label study. Angiographic outcomes were scored by unblinded site investigators. A data safety monitoring board adjudicated hemorrhages.

Enrollment Period: May 2001 to December 2003

Follow-up Duration: 90 days

Centers: 25

Countries: United States

Sample Size: 151

Analysis: The primary outcome was analyzed on an intention-to-treat basis. Secondary outcomes were analyzed based on the cohort in whom the device was deployed, using Fisher exact test and logistic regression.

Inclusion Criteria

Age 18 years or older
Signs and symptoms of acute stroke with NIHSS score ≥8
CT scan of the brain excluding hemorrhage
Stroke symptom duration between 3 and 8 hours, or between 0 and 3 hours with a contraindication for intravenous tPA
Angiographically confirmed occlusion of a treatable large vessel (intracranial carotid, M1, M2, vertebral, or basilar artery)

Exclusion Criteria

Inability to obtain informed consent
Current pregnancy
Serum glucose <50 mg/dL
Excessive vessel tortuosity precluding device access
Known hemorrhagic diathesis or oral anticoagulation with INR >3.0
Significant hypodensity (>1/3 MCA territory) on baseline CT

Baseline Characteristics

Characteristic	Control	Active
Group		Overall Population (n=141)
Age, mean±SD, y		67.0±15.5
Female, %		46
Baseline NIHSS, mean±SD		20.1±6.6
Site of vascular occlusion - Middle cerebral artery, %		57
Site of vascular occlusion - Internal carotid artery, %		19
Site of vascular occlusion - Basilar artery, %		9
Symptom onset to groin puncture, mean hr±SD		4.3±1.7

Arms

Field	Mechanical Embolectomy
Intervention	Attempted mechanical embolectomy using the Merci Retriever device to restore flow in an occluded intracranial large vessel. Up to 6 passes with the device were allowed.
Duration	Single procedure

Outcomes

Outcome	Type	Control	Intervention	HR / OR / RR	P-value
Rate of successful vascular recanalization, defined as achieving Thrombolysis In Myocardial Infarction (TIMI) grade II or III flow in all treatable vessels immediately after treatment with the device.	Primary	18% (Historical Control from PROACT-II)	46% (69/151)	27.70%	<0.0001
Favorable neurological outcome (mRS ≤2) at 90 Days	Secondary	10.4% (Not Recanalized)	46.0% (Recanalized)	RR 4.41 (95% CI, 2.08-9.33)	<0.0001
Mortality at 90 Days	Secondary	54.2% (Not Recanalized)	31.8% (Recanalized)	RR 0.59 (95% CI, 0.39-0.89)	0.0101
Symptomatic intracranial hemorrhage	Adverse		7.8% (11/141)
Clinically significant procedural complications	Adverse		7.1% (10/141)
Device Fracture	Adverse		11 device fractures occurred, contributing to death in 2 patients.

Subgroup Analysis

Multivariate analysis identified revascularization, younger age, lower baseline NIHSS score, shorter procedure time, and left brain infarct as independent predictors of good neurological outcome. No variables predicted successful revascularization.

Criticisms

The study was a single-arm trial that relied on a historical control for its primary efficacy endpoint, which is a major limitation compared to a randomized controlled trial.
Angiographic assessment of recanalization (TIMI score) was performed by unblinded site investigators rather than a blinded central core lab, which could introduce bias.
The study did not report on distal reperfusion or distal emboli, focusing only on the recanalization of the primary occlusion.
The overall mortality rate was high (44%), which, while likely reflecting the severity of the enrolled patient population (median NIHSS 19), cannot be definitively judged as safe without a concurrent control group.

Funding

Concentric Medical Inc.

Based on: MERCI (Stroke, 2005)