Stroke Therapy Gets a New Twist
Corkscrew-like device removes offending clot
THURSDAY, Feb. 5, 2004 (HealthDayNews) -- A miniature "corkscrew" appears to quickly reverse damage suffered from an ischemic stroke.
The first report on the safety and efficacy of the device, called the Concentric MERCIR Retrieval System, will be presented Feb. 5 at the American Stroke Association's annual meeting in San Diego. If approved by the U.S. Food and Drug Administration, this would be the first device specifically designed to remove clots from blood vessels in the brain.
Ischemic strokes are the most common type of brain attack, accounting for almost 90 percent of all cases. They are caused when a blood clot disrupts blood supply to the brain. Once blood flow is stopped, brain cells start to die.
Right now, the only approved treatment is with tissue plasminogen activator (tPA), which dissolves clots, but this therapy takes time to work and must be started within three hours of a stroke to do any good.
"The problem is most people do not show up within three hours and because of that, less than 5 percent -- and closer to 3 percent -- of all people with strokes get this tPA therapy," says Dr. Robert Felberg, director of the Stroke Program at the Ochsner Foundation Clinic and Hospital in New Orleans. "We're all looking for ways to extend the time window."
The new device, made from nickel and titanium, is inserted as a wire into an artery in the groin then guided with standard angiography into the brain and to the blood clot. At the appropriate time, the tip converts into a spiral shape like a corkscrew and "captures" the offending clot. Both the device and the clot are then pulled out into a larger catheter with a balloon.
The initial research involved 114 patients at 25 centers. The Retrieval System managed to restore blood flow in 61 patients, or 54 percent. Of those 61 patients, 23 ended up with no disability or minor disabilities such as problems with handwriting.
"You can imagine the exhilaration with the first patient when we were able to pull out the clot. It sent chills down my spine," says study author Dr. Sidney Starkman, a professor of emergency medicine and neurology at the University of California, Los Angeles, and co-director of the UCLA Stroke Center. "The patient was made almost normal immediately, and these strokes are the most severe strokes."
The study was funded by Concentric Medical Inc. of Mountain View, Calif., which makes the device. The FDA is reviewing the device, Starkman says.
Were the device to be approved, medical personnel would need to be trained and qualified.
The device has a couple of potential advantages over tPA therapy. For one thing, it appears to widen the window of opportunity, possibly to as long as six or eight hours, although this will vary from patient to patient, Starkman says.
Also, the corkscrew device does not carry the same risk as tPA of hemorrhagic stroke, which occurs when a blood vessel inside the brain bursts.
"All strokes have the potential of being converted into hemorrhagic stroke. That could happen without any treatment in a certain percentage of stroke patients," explains Dr. Aman Patel, director of interventional neuroradiology and endovascular neurosurgery at the Mount Sinai School of Medicine in New York City. "If you're giving somebody tPA, the risk and degree of bleeding will be significantly higher. Theoretically, with the corkscrew device, the extent and risk of hemorrhage will be less."
The next step would be to compare tPA directly with the corkscrew retrieval device, Felberg says. "This is promising, but certainly not 100 percent convincing at this point," he adds.
"It's an exciting new product. Would it be the end all and one that works in every patient? Absolutely not," Patel says. "This is just another tool that we can put into our bag. It won't be useful for everybody who presents with a stroke, but I don't think there is going to be one answer."