Ischemic strokes are caused by a blood clot that blocks blood supply to the brain. Each year, about 700,000 Americans suffer a stroke and 88 percent of those strokes are ischemic, according to the American Stroke Association.
Blood clots causing stroke can be dissolved using the FDA-approved clot-busting drug tissue plasminogen activator (tPA) as standard therapy. But, it must be initiated intravenously within three hours (the earlier the better) of stroke onset to be effective.
Moreover, it "typically takes one to two hours for tPA to dissolve a clot and open a vessel, if at all," said Sidney Starkman, M.D., professor of emergency medicine and neurology at the University of California, Los Angeles and co-director of the UCLA Stroke Center.
The investigational device, the Concentric MERCI® Retrieval System, restored blood flow in 61 of 114 patients (54 percent) in Phase I and II of the Mechanical Embolus Removal in Cerebral Ischemia (MERCI I /II) trials, which studied patients up to eight hours after initial stroke symptoms who were not eligible for standard tPA therapy, said principal investigator Starkman.
Restoring blood flow in these trials reversed paralysis and other stroke symptoms, Starkman said.
"How often do we get a chance to reverse a patient's stroke on the table? We have had patients completely paralyzed on one side of their body, who were made normal almost instantaneously when the clot was retrieved," he said.
Of the 61 patients whose arteries were unblocked with the device, "23 have no disability or have minor disability, such as hand writing problems," Starkman said.
The MERCI® Retrieval System is inserted into an artery in the groin, and then carefully guided via standard angiography into the brain until it reaches the blood clots. The device is made from a combination of nickel and titanium, "which is unique in that it allows the device to have a 'memory.' So in this case, when it is deployed, it 'remembers' to form itself into a helical shape, like a corkscrew," Starkman said.
Starkman says the corkscrew-shaped MERCI Retriever is the only device specifically designed to remove clots from all major cerebral vessels.
Once the device "captures" the blood clot, the device and clot are withdrawn into a larger catheter with a balloon. During the evacuation process, the balloon is briefly inflated to momentarily stop blood flow so the clots can be safely removed. Starkman added that the retrieval procedure can only be performed by a highly trained team at specialized centers.
The results presented today are based on 114 patients from 25 centers, (average age 70, 46 percent women), whose average National Institutes of Health baseline stroke score was 19, which indicates severe impairment.
"Thus far, we have seen that the MERCI® Retrieval System is quite safe and we believe it holds great promise, but more research is needed to refine the device and study its effectiveness," Starkman said.
Concentric Medical, Inc. of Mountain View, California funded the studies. The Food and Drug Administration is reviewing the device.
NR04-1203 (ISC04/Starkman)
Abstract 30
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