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BookmarkScienceDaily (Mar. 20, 2007) — If more than three hours pass between the time a patient experiences a stroke and when they arrive at the hospital, it is too late for the only FDA-approved treatment for acute stroke – intravenous tPA, a clot-busting drug. Now a new device called the Merci Retriever – a tiny corkscrew designed to physically remove the source of the stroke, a blood clot in the brain – is giving hope to patients who arrive late. The device is offered to patients as part of an ongoing clinical trial offered at NewYork-Presbyterian Hospital.
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Patients who arrive as long as eight hours after experiencing an acute ischemic stroke are eligible for the study that will compare the device with standard medical management, including the use of antithrombotic drugs and blood-pressure and cholesterol management.
The Phase II clinical trial called MR RESCUE (Magnetic Resonance and REcanalization of Stroke Clots Using Embolectomy) is funded by the National Institutes of Health (NIH).
"Less than about 5 percent of ischemic stroke patients arrive at the hospital within the necessary three-hour window for treatment with medication in most studies. There is an overwhelming need for new treatments for everyone else. We hope to show that the Merci Retriever will be an effective treatment for some of these patients," says Dr. Dana Leifer, lead investigator at NewYork-Presbyterian Hospital/Weill Cornell Medical Center, where he is director of the stroke unit and director of the neurovascular ultrasound laboratory. He is also associate professor of neurology at Weill Cornell Medical College.
"To perform the procedure a catheter is inserted into a leg artery and snaked up to the site of the clot in the brain. The Merci Retriever is then deployed to ensnare the clot, much like inserting a corkscrew into the cork of a wine bottle," says Dr. Ji Chong, lead investigator at NewYork-Presbyterian Hospital/Columbia University Medical Center, where she is assistant attending neurologist. She is also assistant professor of neurology at Columbia University College of Physicians and Surgeons. "The current study requires rapid and coordinated expertise among vascular neurologists, radiologists and interventionalists that only a few hospitals are capable of organizing."
This novel study also uses an urgent MRI to help select patients for consideration of the MERCI device. "We are making progress to extend the window of opportunity to treat acute stroke patients with the combination of advanced imaging and new devices," states Dr. Ralph Sacco, director of the Stroke and Critical Care Division at NewYork-Presbyterian/Columbia and associate chair of neurology and professor of neurology and epidemiology at Columbia University College of Physicians and Surgeons.
The Merci Retriever was first developed in the 1990s by Dr. Pierre Gobin, professor of radiology, professor of radiology in neurological surgery, and professor of radiology in neurology at Weill Cornell Medical College and director of interventional neuroradiology at NewYork-Presbyterian/Weill Cornell. The current version includes a slight modification of threads in the metal retrieval device that preliminary testing has found to better snare blood clots. (Disclosure: Dr. Gobin owns an interest in Concentric Medical of Mountain View, Calif., makers of the device, and will receive royalties from the device's sale.)
The study will also use magnetic resonance imaging (MRI) to locate the blockage in the brain and whether it can be opened, and determine how much damage has been done to brain tissue. The study hopes to identify those patients who will benefit the most from the Retriever.
A previous clinical trial of the Merci Retriever conducted by its developer, Concentric Medical Inc., showed that the Retriever is capable of safely removing clots from stroke patients. Out of 151 patients included in the trial, the Retriever was successful at removing clots 48 percent of the time and procedural complications were low. Based on the results of this trial the Merci Retriever was approved by the FDA as a device to remove clots, but not as a treatment for acute ischemic stroke.
More than 20 hospitals in North America are participating in the randomized trial and a total of 120 patients are expected to be enrolled. The trial is led by the University of California, Los Angeles.
