Elsevier

The Lancet

Volume 380, Issue 9849, 6–12 October 2012, Pages 1241-1249
The Lancet

Articles
Solitaire flow restoration device versus the Merci Retriever in patients with acute ischaemic stroke (SWIFT): a randomised, parallel-group, non-inferiority trial

https://doi.org/10.1016/S0140-6736(12)61384-1Get rights and content

Summary

Background

The Solitaire Flow Restoration Device is a novel, self-expanding stent retriever designed to yield rapid flow restoration in acute cerebral ischaemia. We compared the efficacy and safety of Solitaire with the standard, predicate mechanical thrombectomy device, the Merci Retrieval System.

Methods

In this randomised, parallel-group, non-inferiority trial, we enrolled patients from 18 sites (17 in the USA and one in France). Patients were eligible for inclusion if they had acute ischaemic stroke with moderate to severe neurological deficits and were treatable by thrombectomy within 8 h of stroke symptom onset. We used a computer-generated randomisation sequence to randomly allocate patients to receive thrombectomy treatment with either Solitaire or Merci (1:1; block sizes of four and stratified by centre and stroke severity). The primary endpoint was Thrombolysis In Myocardial Ischemia (TIMI) scale 2 or 3 flow in all treatable vessels without symptomatic intracranial haemorrhage, after up to three passes of the assigned device, as assessed by an independent core laboratory, which was masked to study assignment. Primary analysis was done by intention to treat. A prespecified efficacy stopping rule triggered an early halt to the trial. The study is registered with ClinicalTrials.gov, number NCT 01054560.

Results

Between February, 2010, and February, 2011, we randomly allocated 58 patients to the Solitaire group and 55 patients to the Merci group. The primary efficacy outcome was achieved more often in the Solitaire group than it was in the Merci group (61% vs 24%; difference 37% [95% CI 19–53], odds ratio [OR] 4·87 [95% CI 2·14–11·10]; pnon-inferiority<0·0001, psuperiority=0·0001). More patients had good 3-month neurological outcome with Solitaire than with Merci (58% vs 33%; difference 25% [6–43], OR 2·78 [1·25–6·22]; pnon-inferiority=0·0001, psuperiority=0·02). 90-day mortality was lower in the Solitaire group than it was in the Merci group (17 vs 38; difference −21% [–39 to −3], OR 0·34 [0·14–0·81]; pnon-inferiority=0·0001, psuperiority=0·02).

Interpretation

The Solitaire Flow Restoration Device achieved substantially better angiographic, safety, and clinical outcomes than did the Merci Retrieval System. The Solitaire device might be a future treatment of choice for endovascular recanalisation in acute ischaemic stroke.

Funding

Covidien/ev3.

Introduction

Occlusion of proximal intracranial arteries is a common cause of acute ischaemic stroke and causes much disability and mortality.1, 2, 3 Treatments for ischaemic stroke that are approved by guidelines or regulatory authorities include systematic supportive care in a stroke unit or stroke centre, prevention of clot propagation with aspirin, and achievement of reperfusion through use of intravenous recombinant tissue plasminogen activator (rt-PA) until 4·5 h after onset, intra-arterial fibrinolysis until 6 h after onset, and mechanical thrombectomy until 8 h after onset.4, 5 Available intravenous and endovascular reperfusion techniques are restricted in the extent to which they achieve recanalisation and avoid intracranial haemorrhage, so the development of new devices with different approaches to thrombus removal is desirable.6, 7, 8, 9, 10, 11

The Solitaire Flow Restoration device (Covidien/ev3, Dublin, Ireland) is a self-expanding stent retriever designed to restore blood flow in patients with ischaemic stroke due to large intracranial vessel occlusion. When the stent is deployed within the target clot in the occluded vessel, the stent struts entrap the thrombus. When the stent is withdrawn in its unfolded state, the enmeshed thrombus is concurrently extracted from the vessel. In a pig vessel occlusion model, the Solitaire device achieved rapid and complete recanalisation of target arteries without pathological evidence of vessel damage related to device deployment.12 In several open, uncontrolled clinical series, the Solitaire device has yielded high rates of reperfusion and favourable clinical outcomes in patients with acute ischaemic stroke.13, 14, 15, 16, 17 The Merci Retriever (Stryker; Kalamazoo, MI, USA) is a family of corkscrew-shaped devices consisting of flexible nitinol wire with coil loops, of regular or variable pitch, some with arcading filaments attached. Once deployed, it assumes its coiled shape to engage and extract the clot.18 The Merci Retriever was the first mechanical thrombectomy device cleared by regulatory authorities in the USA for use in acute ischaemic stroke, in 2004.

We describe the results of the Solitaire With the Intention For Thrombectomy (SWIFT) trial, a multicenter, prospective, randomised, blinded endpoint assessment trial comparing the efficacy and safety of neurothrombectomy with Solitaire versus the contemporary regulatory standard, the Merci Retriever.

Section snippets

Study design and participants

SWIFT was a multicenter, randomised, prospective, parallel-group trial with blinded primary endpoint ascertainment. Details of the study design are available elsewhere.19 Briefly, patients were eligible if they had acute ischaemic stroke with moderate to severe neurological deficits, harboured angiographically confirmed occlusions of proximal cerebral arteries, and were treatable by thrombectomy within 8 h of stroke symptom onset. Key inclusion criteria included age (22–85 years), National

Results

Between February, 2010, and February, 2011, 18 sites (17 in the USA and one in France) consented and enrolled 144 patients, including 31 roll-in patients who received Solitaire and 113 patients who were randomly allocated to one of the two treatment groups (58 to Solitaire and 55 to Merci; figure 1). After a safety review in February, 2011, the data and safety monitoring board recommended that enrolment be placed on hold and the interim efficacy analysis be undertaken earlier than initially

Discussion

Our study suggests that, compared with the Merci Retriever, neurothrombectomy with the Solitaire Flow Restoration device is associated with increased achievement of successful cerebral recanalisation without symptomatic intracranial haemorrhage, improved final disability outcomes, and reduced mortality.

The combined primary efficacy endpoint in our trial, successful recanalisation with no symptomatic haemorrhage, was selected at the request of regulatory authorities and is novel in neurovascular

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