NEW ORLEANS – An investigational clot-retrieval device completely recanalized blocked cerebral arteries, improved neurologic outcomes, and significantly reduced mortality from acute ischemic stroke more often than did the widely used Merci device in a randomized, open-label trial.
The SWIFT (SOLITAIRE-FR With the Intention for Thrombectomy) study intended to randomize 200 patients with ischemic stroke to treatment with either of the devices, but after 18 months, the trial’s data safety monitoring board stopped the study with 144 patients treated, citing "an overwhelming benefit" of the Solitaire-Flow Restoration device over the Merci device, Dr. Jeffrey Saver said at the International Stroke Conference.
Dr. Jeffrey L. Saver
"With these results, we see for the first time a highly effective cerebral recanalization procedure for ischemic stroke," said Dr. Saver, director of the stroke unit at the University of California, Los Angeles, in an interview. "[Tissue plasminogen activator] opens the arteries partially 40% of the time and completely just 5% of the time. This device opens them completely 60% of the time. It’s a dramatic step forward and a device that will probably be a game-changer for our systems, once it becomes available."
Solitaire is a columnar metal cage which, when expanded, engages the clot at multiple points, facilitating extraction and decreasing the chance of symptomatic intracranial bleeding. The Merci device, a corkscrew-like coil, does release pressure on the atrial wall, "but has a tendency to uncoil and fail to engage the clot," he said.
The patients’ average age was 67 years; most (68%) were male. The median pre-stroke modified Rankin Scale score was 0.5. Time to first angiogram was 4-5 hours.
The primary end point – successful recanalization without symptomatic intracranial hemorrhage – occurred in 61% of the Solitaire group and 24% of the Merci group. This was a highly significant difference with a P value of .0001 in both noninferiority and superiority analyses.
The trial’s secondary end points also indicated the superiority and noninferiority of Solitaire in comparison with Merci:
• Use of rescue therapy (21% vs. 44%).
• Symptomatic intracranial hemorrhage (2% vs. 11%).
• All intracranial hemorrhage (17% vs. 38%).
• Good 90-day neurologic outcome (58% vs. 33%).
• 90-day mortality (17% vs. 38%).
The investigators defined a good neurologic outcome as a modified Rankin Scale score of 0-2 if a patient came in at that level, if the patient returned to their baseline score after coming in with a worse score, or for patients who achieved at least a 10-point increase in their National Institutes of Health Stroke Scale score also were assessed as having a good outcome.
The results demonstrate an excellent number-needed-to-treat analysis, Dr. Saver said.
"For every 2.7 patients treated, 1 additional patient had a successful recanalization with no brain bleed. For every five patients treated, one patient was saved from death. And for every four patients treated, there was one more with a good neurologic outcome."
Device fracture occurred in two instances with Solitaire but in no cases with Merci. There were two instances with each device in which the device could not be delivered appropriately. Air embolism occurred in one patient with each device. Vasospasms occurred in eight cases with Solitaire and six cases with Merci. Two patients undergoing interventions with the Merci device had vessel perforations, compared with none who were treated with the Solitaire device. Distal emboli occurred with Solitaire in two patients and with Merci in three patients.
The study design included a "roll-in" period in which the investigators learned how to perform the interventions; 31 patients were treated during this time, while the remaining 113 were randomized to treatment with the Merci device (55) or the Solitaire (58). All of the patients either were ineligible for tissue plasminogen activator or had failed a treatment.
Each patient received up to three passes of the assigned device. A separate lab, blinded to treatment arms, reviewed scans of the treated arteries. If the clot remained, physicians could try other appropriate treatments.
While SWIFT decisively proved Solitaire’s capability as a clot retriever, it didn’t have the chance to explore the device’s other possible indication as a stent, Dr. Saver added.
‘This device is designed to pull the clot out or, if that fails, you can detach the stent portion and leave it in place. But what we experienced in this study was that it was getting the clot out so often, we weren’t able to test it as a stenting device."
In fact, for some patients, Solitaire may be more suited as a stent than as a retrieval device. "I think that for a patient who has plaques in the intracranial arteries and a little bit of clot on top of the plaque, retrieval is not the best strategy. The devices tend to snag on the hard edges of the plaque. Those patients are best treated with a stenting approach, which may possible with his device."