A More Effective Revascularization Device for Stroke?
NEW ORLEANS—The experimental Solitaire flow restoration device is superior to the Merci Retrieval System in achieving recanalization free of symptomatic hemorrhagic transformation in patients with acute ischemic stroke, according to research presented at the 2012 International Stroke Conference.
Jeffrey L. Saver, MD, lead study author and Professor of Neurology and Director of the Stroke Center at the Geffen School of Medicine, University of California in Los Angeles, reported results of the Solitaire With the Intention for Thrombectomy (SWIFT) trial, a multicenter, randomized, noninferiority study that was the first of its kind to directly compare revascularization techniques. Compared with the FDA-approved Merci retriever, “initial treatment with the Solitaire device is associated with more frequent reperfusion, less symptomatic intracranial hemorrhage, reduced mortality, and increased good final neurologic outcome three months after stroke,” said Dr. Saver.
The Solitaire device is a self-expanding stent retriever, with a favorable metal-to-tissue ratio, that is intended for use in 2- to 5.5-mm blood vessels. Dr. Saver described Solitaire as a “metal cage” that “engages the clot at multiple strut points,” which may make it more effective at pulling out the clot. In contrast, the Merci retriever is a helical coil that tends to unwind as it is pulled through the clot, which “may keep it from engaging the clot as frequently as a different type of design,” he noted.
The investigators tested the two devices at 21 sites (20 in the United States, one in Europe) and incorporated a roll-in period for sites that had no experience using the Solitaire device. Once sites completed the roll-in period, the patients, all with clinical signs consistent with ischemic stroke, were randomized to either the Solitaire group or the Merci group.
All participants (ages 22 to 85) had scores on the NIH Stroke Scale ranging from 8 to 29 and had experienced proximal intracranial occlusion. According to Dr. Saver, those enrolled in the study “were generally very similar in their baseline features.” However, 44.8% of those randomized to Solitaire had atrial fibrillation, compared with 67.3% of those randomized to Merci.
Eligible patients needed to be treated within eight hours of stroke onset. Some patients were ineligible for IV t-PA, and others received t-PA treatment but did not respond to it.
Of the 144 patients enrolled by the end of the study, 31 were treated in the roll-in phase and 113 in the randomized phase. Fifty-eight patients were randomized to receive initial treatment with the Solitaire device, and 55 patients were randomized to receive initial treatment with the Merci device.
The study’s primary efficacy endpoint was successful recanalization with the assigned study device and without symptomatic intracranial hemorrhage. After up to three passes of either assigned device, a core laboratory that was blinded to which treatment that patients received then assessed whether the artery was reopened.
Favorable Results for Solitaire
The Solitaire device was more effective than the Merci retriever at achieving successful recanalization without intracranial hemorrhage, according to Dr. Saver. As a result, although the researchers had planned to randomize 200 patients, the SWIFT trial was halted after it met the pre-established interim efficacy stopping rule in July 2011, when only 144 patients had been enrolled.
Results showed that 60.7% of patients in the Solitaire group were successfully recanalized without intracranial hemorrhage, while 24.1% of patients in the Merci group experienced a successful outcome. According to Dr. Saver, the results were “highly statistically significant.”
Patients who received the Solitaire device also had better clinical outcomes, said Dr. Saver. At three months follow-up, 58.2% of patients treated with the Solitaire device had a good neurologic outcome, compared with 33.3% of patients treated with the Merci device.
Furthermore, the mortality of patients in the Solitaire group was 17.2% at three months versus 38.2% in the Merci group, and symptomatic intracranial hemorrhages occurred in 1.7% of patients treated with the Solitaire device and in 10.9% of those treated with Merci. All types of intracranial hemorrhages were observed in 17.2% of patients who received the Solitaire device and in 38.2% of those who received the Merci device. Study device–related significant adverse events occurred in 8.6% of those randomized to Solitaire and in 16.4% of persons randomized to Merci.
FDA Review Under Way
Dr. Saver noted the potential advantages of using the Solitaire device rather than the Merci. “For every five patients treated, one more patient will not die, and for every four patients treated, one more patient would have a good neurologic final outcome,” he said. “t-PA only opens arteries partially 40% of the time.…This device opens arteries completely 60% of the time. That’s really a dramatic step change.
