Clot Retrieval Devices Show Improved Results in Acute Ischemic Stroke Patients

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A pair of randomized trials shows that 2 novel ‘stent-on-a-wire’ thrombectomy devices are superior to an older system in treating acute ischemic stroke patients who have failed or are not candidates for intravenous (IV) thrombolytic therapy, one even showing an improvement in mortality. The reports were published online August 26, 2012, ahead of print in the Lancet.

In the TREVO 2 trial, researchers led by Raul G. Nogueira, MD, of the Emory University School of Medicine (Atlanta, GA), randomized 170 acute ischemic stroke patients with large artery occlusions ineligible or refractory to intravenous t-PA to treatment with the Trevo Retriever (n = 88; Stryker Neurovascular, Mountain View, CA) or an older, predecessor model, the Merci device (n = 90; Stryker Neurovascular).

New Class of Stent Retrieval Devices

The Trevo thrombectomy device, part of a growing class of ‘stent retrievers,’ applies a radial force in the center of the thrombus and along its whole length. A microcatheter is placed distal to the thrombus to deliver the closed-cell stent-like nitinol device. The retriever is deployed by unsheathing the microcatheter, resulting in opening of the stent and radial displacement of the thrombus against the blood vessel wall with incorporation of the clot material into the stent struts. The device, along with the clot, is subsequently retrieved into a catheter placed in the internal carotid or vertebral arteries.

In the trial, the primary efficacy endpoint of revascularization success, defined as TICI (thrombolysis in cerebral infarction) perfusion grade 2 or greater, was 86% in Trevo patients vs. 60% in patients who received the Merci device, which has been approved in the United States since 2004. The difference met the trial’s definition for noninferiority (P < 0.0001) as well as superiority (P < 0.0001) for the Trevo device compared with the Merci retriever.

In addition, good clinical outcome at 90 days (modified Rankin score of 0-2) was improved in Trevo patients (40% vs. 22%; P = 0.0130). Safety outcomes, including the primary safety endpoint of 24-hour procedure-related adverse events, were equivalent between groups, with the exception of vessel perforations, which were more common with the Merci device (table 1).

Table 1. Safety Outcomes

“Our trial showed that the Trevo Retriever was superior to the Merci Retriever for arterial revascularization in terms of reperfusion to TICI 2 or greater in the setting of acute ischemic stroke,” the researchers conclude, adding that a trial of endovascular therapy with the Trevo device vs. medical therapy in this setting is now warranted.

In the second study, researchers led by Jeffrey L. Saver, MD, of the University of California, Los Angeles, David Geffen School of Medicine (Los Angeles, CA), randomized 113 stroke patients who either failed or were not candidates for t-PA to treatment with the Solitaire system (n = 58; Covidien/ev3, Dublin, Ireland) or the Merci device. Solitaire is a stent retriever device in the same class as the Trevo device.

Results for the multicenter SWIFT (Solitaire With the Intention for Thrombectomy) trial were initially presented February 3, 2012, at the American Stroke Association’s annual International Stroke Conference in New Orleans, LA.

After an interim analysis, the trial was halted a year early due to the positive results encountered with the Solitaire device. The primary endpoint, successful recanalization with no symptomatic intracranial hemorrhage or rescue therapy, was significantly improved with the Solitaire device compared with the Merci retriever system. Other endpoints, such as core lab-adjudicated recanalization, use of rescue therapy, symptomatic intracranial hemorrhage, good neurologic outcome, and mortality, were also better with Solitaire (table 1).

Table 1. Primary, Secondary Outcomes

^a P values for superiority and noninferiority met for all endpoints.

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

Both the Trevo and Solitaire devices were cleared for use in recent months by the US Food and Drug Administration (Trevo in August 2012 and Solitaire in March 2012).

Clot Retrieval Becoming Mainstream?

In a telephone interview with TCTMD, L. Nelson Hopkins, MD, of University at Buffalo Neurosurgery (Buffalo, NY), noted that the newer devices show that “the technology development in this space is an iterative process. We’re going to see step by step improvement in the technology used to remove clots and eventually clot retrieval in stroke will become mainstream. In practice, more and more physicians are getting comfortable with using these devices and that’s why we’re starting to see better results.”

He described the older Merci device as a single, cork-screw-shaped wire that does not exert the same outward radial force of the newer devices and can become straight as it is pulled through a blockage if there is significant adherence to the vessel wall.

Dr. Hopkins called the concept behind the clot retrieval devices “incredibly logical,” and likened it to what occurs with acute MI revascularization. “If a major artery is blocked going to a major organ and you can get that artery unblocked in time to salvage the tissue, then you’ve got a chance to create a meaningful recovery whereas prior to this, patients had no chance.”

He noted that IV t-PA is still preferred by the neurologic community and considered the current state of the art for acute stroke treatment, but only if patients present within the 3-hour time window from symptom onset. In practice, however, “the great majority of cases are not good candidates for IV t-PA primarily because they’re outside the treatment window, they don’t get there in time,” Dr. Hopkins said.

‘I Don’t Care What the Time Window Is’

But even if they do, clot retrieval devices may be a good option, he added. “In major strokes, IV t-PA is usually of very little value,” Dr. Hopkins said. “If a major artery like a middle cerebral is blocked by a clot, IV t-PA is not likely to open that. My personal feeling is we’re going to see data coming down the road that show if you’ve got a major artery blocked, I don’t care what the time window is, you’re going to be better off reopening the artery and IV t-PA is not likely to do that. It’s just like acute MIs: Thrombolytic therapy worked, but it wasn’t very effective.”

Along these lines, in an editorial accompanying the study, Philip B. Gorelick, MD, MPH, of the Michigan State University College of Human Medicine (Grand Rapids, MI), notes that future trials of current and newer clot retrieval devices “will need to take into account comparison or complementary treatment with rt-PA, or with newer-generation thrombolytics such as desmoteplase and tenecteplase.”

In the meantime, “SWIFT and TREVO 2 are major steps forward in the successful treatment of acute ischaemic stroke, and pave the way for new treatment options and further validation by additional trials and post-marketing registry data,” Dr. Gorelick concludes.

 

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Sources:
1. Nogueira RG, Lutsep HL, Gupta R, et al. Trevo versus Merci retrievers for thrombectomy revascularization of large vessel occlusions in acute ischaemic stroke (TREVO 2: A randomised trial. Lancet. 2012;Epub ahead of print.

2. Saver JL, Jahan R, Levy EI, et al. Solitaire flow restoration device versus the Merci Retriever in patients with acute ischaemic stroke (SWIFT): A randomised, parallel-group, non-inferiority trial. Lancet. 2012;Epub ahead of print.

3. Gorelick PH. Assessment of stent retrievers in acute ischaemic stroke. Lancet. 2012;Epub ahead of print.

 

 

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