Small Study Supports Thrombectomy Devices in Large Strokes

A new class of stent retrieval device shows positive results in treating large, acute ischemic stroke, demonstrating favorable outcomes compared with thrombolytic therapy. The findings, from a small patient series, were published online October 2, 2012, ahead of print in Stroke.

Researchers led by Ronen R. Leker, MD, of Hebrew University-Hadassah Medical Center (Jerusalem, Israel), looked at 88 patients with acute middle cerebral artery (MCA) infarcts who received treatment with t-PA (n = 66) or the Solitaire thrombectomy device (n = 22; Covidien/ev3, Dublin, Ireland). The Solitaire device, which features a wire attached to a self-expanding stent, can be fully deployed and then retrieved, capturing and removing the clot along the way.

In the study, baseline characteristics were similar between the Solitaire group and the t-PA group, with no differences in risk-factor profile or presumed stroke etiology. Solitaire patients received treatment much later than those receiving t-PA (234.3 minutes vs. 134.2 minutes; P < 0.001). Half of the Solitaire patients had poor collaterals. Nevertheless, recanalization was achieved rapidly (median 44 minutes) with high rates of thrombolysis in cerebral infarction grade 2b-3 (95%). Symptomatic intracranial hemorrhage (5% vs. 8%) and any intracerebral hemorrhage (14% vs. 12%) were similar between the 2 groups.

Outcomes Favor Thrombectomy

Improvement in NIH stroke scale score from baseline to discharge was greater in the Solitaire group (11.6 vs. 6.4; P < 0.001) despite a similar median length of hospital stay (14.7 days vs. 13.3 days; P = 0.51). In addition, favorable outcome according to modified Rankin Scale was achieved in more than half of the Solitaire patients (60%) compared with 37.5% of t-PA patients (P = 0.001).

The overall shift toward more favorable outcomes was significant in Solitaire patients compared with t-PA patients, reflected in modified Rankin Scale scores (table 1).

Table 1. Modified Rankin Scale Score at 90 Days

^a P = 0.001 for overall difference in scores.

Mortality at 90 days was higher in Solitaire patients, but the difference was not statistically significant (29% vs. 17%; P = 0.75).

On multivariable analysis, predictors of unfavorable outcome were age (OR 0.89; 05% CI 0.84-0.95; P < 0.001) and admission NIH stroke scale score (OR 0.77; 95% CI 0.65-0.91; P = 0.003), but not treatment allocation to the Solitaire device (OR 2.43; 95% CI 0.35-16.9; P = 0.37).

The researchers conclude that “treatment with [stent-based thrombectomy] may be at least as efficacious as t-PA in patients with large hemispheric infarcts,” and that “because early recanalization is an important modulator of outcome, our results suggest that earlier treatment with [stent-based thrombectomy] may have larger impacts on outcome compared with systemic thrombolysis.”

Dr. Leker and colleagues acknowledge that the 2 groups in their study may represent different types of stroke patients. “Nevertheless,” they note, “the similarities in baseline characteristics and the fact that [stent-based thrombectomy] was completed early within the time frame of mechanical thrombectomy allow for a close enough comparison with real-life experience for use of t-PA.”

‘Game Changers’

According to Elad I. Levy, MD, of University at Buffalo, State University of New York (Buffalo, NY), the current class of stent retriever devices is most effective in large occlusion-strokes, as shown in the current report. “Though t-PA is very effective in small-branch occlusion, it’s not as effective in large branches and has a higher re-hemorrhage rate,” he told TCTMD in a telephone interview. “It’s good to have both tools, but these thrombectomy devices are really game changers.”

He described what he saw as “a fervor” among clinicians in their eagerness to use the devices. “People are very eager to adopt and use them,” Dr. Levy said. “These stent retrievers are definitely iterative advances in technology. They’re often not difficult to use, and they navigate easily, and we’ve had great success with them.”

A key reason for this, he noted, is the restrictive time window within which t-PA is effective. “It’s a big deal [because] very few patients are going to make it to the hospital in four-and-a-half hours,” Dr. Levy said. “By extending the time window to 6 or 8 hours, depending on the device or study protocol, you’re basically almost doubling the time window and you’re going to be able to include a lot more patients for treatment.”

However, Philip M. Meyers, MD, of Columbia University Medical Center (New York, NY), disagreed, noting that the longer time window for thrombectomy devices is not based on hard evidence. “The early trials arbitrarily set 8 hours as the time period you can go out to for using these devices,” he told TCTMD in a telephone interview. “There’s no data to say you really can go out to 8 hours, we’re hoping that’s true. Probably for a lot of patients, their stroke is done maybe 1 or 2 hours into it before you ever get a chance to get your hands on them.”

Paradigm Yet to Take Off

Overall, Dr. Meyers agreed that the current thrombectomy devices “are showing promise,” but added, “show me some proof in a controlled, randomized trial so we can get this whole endovascular stroke treatment paradigm off the ground. Even though we have little studies like this that show what looks like powerful benefit, whenever we try to apply these devices in a real trial, the patients overall just don’t do well.”

As an example, he pointed to the Interventional Management of Stroke 3 (IMS 3) trial, which was halted in April 2012 for futility. IMS 3 was designed to compare IV t-PA alone vs. t-PA plus either intra-arterial t-PA or mechanical thrombectomy in stroke patients. The trial was stopped after an interim analysis revealed that the combination therapy could not prove superiority.

“If only we could come up with a test in neurology that lets us pick out that group [most likely to benefit from thrombectomy], because I think it’s small,” Dr. Meyers said. “Where these trials keep getting shot down is we try to address this broad group of patients who maybe are eligible up to 8 hours, but a lot of them really aren’t so the results come out looking bad. It’s not that the device doesn’t work.”

Study Details

On admission, Solitaire patients had worse median NIH stroke scale scores (21 vs. 14.5; P < 0.001) and more frequent large lesions on CT (32% vs. 12%), though the difference was not significant (P = 0.3).

Source:

Leker RR Eichel R, Gomori JM, et al. Stent-based thrombectomy versus intravenous tissue plasminogen activator in patients with acute middle cerebral artery occlusion. Stroke. 2012;Epub ahead of print.

Disclosures:

• The study was supported in part by the Scheinberg Cerebrovascular Fund and by the Juni Trust Fund.
• Dr. Leker reports no relevant conflicts of interest.
• Dr. Levy reports serving as the principal investigator for the upcoming SWIFT PRIME trial, which will involve treatment of stroke patients with the Solitaire device.
• Dr. Meyers reports serving as the external monitor for the IMS 3 trial.

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