Studies Published Supporting Next-Generation Reperfusion Devices for Stroke Treatment

August 26, 2012—The Lancet announced the publication of studies that demonstrated the potential of two mechanical clot-retrieval devices for the treatment of stroke patients who are not eligible for or fail to respond to drug treatment. Data from the SWIFT study of the Solitaire flow restoration (FR) device (Covidien, Mansfield, MA) were published by Jeffrey Saver, MD, et al. Results from TREVO 2, a study of the Trevo device (Stryker Corporation, Kalamazoo, MI), were published by Raul Nogueira, MD, et al.

Both studies compared the safety and effectiveness of their respective devices to Stryker's first-generation Merci Retriever system, which received US Food and Drug Administration clearance in 2004. Covidien's Solitaire FR device is not yet approved in the United States, but it is available in Europe. The TREVO 2 data are currently being used in a 510(k) submission to the US Food and Drug Administration to seek clearance of Stryker's next-generation Trevo Pro Retriever.

According to The Lancet, the double-blind, randomized SWIFT trial of 113 patients found that patient outcomes were significantly improved in the group who had been treated with the Solitaire FR device, with 58% being assessed as having a good neurological outcome after 3 months compared to 33% of those treated with the Merci retriever. Additionally, patient deaths were reduced from 38% with Merci to 17% with Solitaire FR. On February 3, the American Stroke Association announced that Dr. Saver presented the Covidien-sponsored SWIFT trial data at the 2012 International Stroke Conference in New Orleans, Louisiana.

TREVO 2 found that the chance of living a fully independent life after stroke was significantly higher with Trevo (40%) as compared to Merci (22%). On May 24, Stryker announced that Dr. Nogueira presented the results of the Stryker-sponsored TREVO 2 clinical trial at the 2012 European Stroke Conference in Lisbon, Portugal. 

The Lancet noted that both the Trevo and Solitaire FR devices were significantly more adept in restoring blood flow in affected arteries when compared to the Merci device, although the two trials used different definitions of reperfusion and favorable neurological outcomes, precluding any direct comparison between the Trevo and Solitaire FR devices on the basis of these studies.


Both devices appear to have similar or improved safety profiles when compared to the Merci retriever. They have both also been cleared for general clinical use in the US and Europe, and the results suggest that if the findings are confirmed by further studies, significant improvements could be forthcoming for stroke patients in whom drug treatment is ineffective.


As summarized in The Lancet's abstract of the SWIFT study, the Solitaire FR self-expanding stent retriever is designed to yield rapid flow restoration in acute cerebral ischemia. SWIFT is a randomized, parallel group, noninferiority trial that enrolled patients from 18 sites (17 in the United States and one in France). Patients were eligible for inclusion if they had acute ischemic stroke with moderate-to-severe neurological deficits and were treatable by thrombectomy within 8 hours of stroke symptom onset.

The investigators used a computer-generated randomization sequence to randomly allocate patients to receive thrombectomy treatment with either Solitaire FR or Merci (1:1; block sizes of four and stratified by center and stroke severity). The primary endpoint was TIMI grade 2 or 3 flow in all treatable vessels without symptomatic intracranial hemorrhage after up to three passes of the assigned device. The endpoint was 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, advised the investigators.

In The Lancet, the SWIFT investigators reported that between February 2010 and February 2011, they randomly allocated 58 patients to the Solitaire FR group and 55 patients to the Merci group. The primary efficacy outcome was achieved more often in the Solitaire FR group than it was in the Merci group (61% vs 24%; difference 37% [95% confidence interval [CI], 19–53], odds ratio [OR], 4.87 [95% CI, 2.14–11.1]; P_{noninferiority} < .0001; P_superiority = .0001). More patients had favorable 3-month neurological outcomes with Solitaire FR than with Merci (58% vs 33%; difference 25% [6–43], OR, 2.78 [1.25–6.22]; Pnoninferiority = .0001; P_superiority = .02). Furthermore, 90-day mortality was lower in the Solitaire FR group than it was in the Merci group (17 vs 38; difference –21% [–39 to –3], OR, 0.34 [0.14–0.81]; P_{noninferiority} = .0001; P_superiority = .02).

The SWIFT investigators concluded that the Solitaire FR device achieved substantially better angiographic, safety, and clinical outcomes than the Merci retrieval system and that the Solitaire FR device might be a future treatment of choice for endovascular recanalization in acute ischemic stroke patient.

In the abstract of their report, the TREVO 2 investigators noted that current mechanical devices are unable to achieve recanalization in up to 20% to 40% of large-vessel occlusion strokes. TREVO 2 is an open-label, randomized controlled trial that enrolled patients at 26 sites in the US and one in Spain. The investigators included patients aged 18 to 85 years with angiographically confirmed large-vessel occlusion strokes and US National Institutes of Health Stroke Scale scores of 8 to 29 within 8 hours of symptom onset. Patients were randomly assigned (1:1) with sequentially numbered sealed envelopes to thrombectomy with Trevo or Merci devices. Randomization was stratified by age (≤ 68 years vs 69–85 years) and National Institutes of Health Stroke Scale scores (≤ 18 vs 19–29), with alternating blocks of various sizes.

The primary efficacy endpoint, as assessed by an unmasked core laboratory, was thrombolysis in cerebral infarction scores of 2 or increased reperfusion with the assigned device alone. The primary safety endpoint was a composite of procedure-related adverse events. Analyses were done by intention to treat.

As summarized in The Lancet abstract, between February 3, 2011, and December 1, 2011, 88 patients were randomly assigned to the Trevo group and 90 patients to Merci group. Of these patients, 76 (86%) in the Trevo group and 54 (60%) in the Merci group met the primary endpoint after the assigned device was used (OR, 4.22; 95% CI, 2.01–8.86; P_superiority < .0001). The incidence of the primary safety endpoint did not differ between groups (13 patients [15%] in the Trevo group vs 21 [23%] in the Merci group; P = .1826).

The TREVO 2 investigators concluded that patients who have had large-vessel occlusion strokes but are ineligible for (or refractory to) intravenous tissue plasminogen activator should be treated with the Trevo retriever in preference to the Merci retriever.

In a commentary also published online in The Lancet, Philip B. Gorelick, MD, of the Hauenstein Neuroscience Center and Michigan State University College of Human Medicine, considered the implications of these studies.

“The SWIFT and TREVO 2 studies, although modest in sample size, begin to answer the call for high-level evidence about the efficacy and safety of mechanical clot retrieval devices in acute ischemic stroke,” stated Dr. Gorelick. “It will be interesting to learn, on the basis of future nonprimary analyses, whether collateral flow patterns or clot characteristics elucidate propensity for treatment response.”

Dr. Gorelick concluded, “Future randomized trials of these and other, newer devices will need to take into account comparison or complementary treatment with rtPA or with newer-generation thrombolytics such as desmoteplase and tenecteplase. SWIFT and TREVO 2 are major steps forward in the successful treatment of acute ischemic stroke and pave the way for new treatment options and further validation by additional trials and postmarketing registry data.”