WASHINGTON – The first randomized controlled study to evaluate a procedure that removes blood clots in the brain from patients experiencing severe strokes finds it delivers no better outcomes than non-invasive standard medications. In addition, the study found imaging techniques were not helpful in identifying patients who potentially would benefit most from clot removal.
The study, led by a Georgetown University Medical Center researcher, was published online today in the New England Journal of Medicine and simultaneously presented at the International Stroke Conference in Honolulu, Hawaii.
"The hope was, and to some degree still is, that if you pull out the clot within a certain period of time and there is salvageable brain tissue, there will be better outcomes," said lead researcher Chelsea Kidwell, M.D., professor of neurology and director of the Stroke Center at Georgetown University Medical Center.
Currently, the only proven effective treatment for a stroke caused by a blood clot (ischemic) is tPA (tissue plasminogen activator). The treatment, administered in the hospital, must be given within the first few hours after stroke symptoms appear. For patients who don't meet the timeline for treatment or whose clots do not respond to tPA, an interventional procedure to remove the is another option.
The study, named MR RESCUE (Mechanical Retrieval and REcanalization of Stroke Clots Using Embolectomy), was conducted at 22 institutions in the U.S. The trial evaluated outcomes in 118 patients at an average age of 65.5 who had suffered a severe ischemic stroke in one of the large blood vessels carrying blood to the front of the brain (the most common location for this type of stroke).
By removing the clot within the first eight hours of having the stroke, researchers hypothesized that the procedure would restore blood flow to the affected area of the brain. Prior to conducting the procedure, the patients received an array of MRI or CT scans, including a blood flow study, to help identify those with viable brain tissue who presumably would benefit if the clot was removed and blood flow restored.
After imaging studies were processed using study-specific software to determine if substantial salvageable brain tissue was present, the patients were randomized to receive either standard medical treatment (aspirin or other medicine) or clot removal with a special device. Patients who received tPA were allowed to enroll in the study if the treatment failed. Tools used to remove the clot included the MERCI Retriever (a tiny corkscrew-like device) or the Penumbra System (an aspiration device).
Researchers found no greater overall benefit in patients who had their clot removed compared to standard medicines. More specifically:
- The level of disability 90 days after stroke was no different in patients who received medical care or clot removal.
- The rates of death (21 percent) and symptomatic brain bleeds (4 percent) were no different in the two treatment groups.
- Response to clot removal was no better in the 58 percent of patients with a favorable imaging pattern that suggested salvageable brain tissue.
Kidwell says these findings may not apply to the newer clot removal tools that can open vessels better and faster. "The safety data for these tools examined in this study are encouraging, which is important as we move forward to evaluate newer and possibly better devices," she said
Reza Jahan, M.D., associate professor of interventional neuroradiology at the University of California, Los Angeles, is co-principal investigator of the study. Other authors include: Jeffrey Gornbein, Dr.P.H.; Jeffry R. Alger, Ph.D.; Val Nenov, Ph.D.; Zahra Ajani, M.D.; Lei Feng, M.D., Ph.D.; Brett C. Meyer, M.D.; Scott Olson, M.D.; Lee H. Schwamm, M.D.; Albert J. Yoo, M.D.; Randolph S. Marshall, M.D., M.S.; Philip M. Meyers, M.D.; Dileep R. Yavagal, M.D.; Max Wintermark, M.D.; Judy Guzy, R.N.; Sidney Starkman, M.D.; and Jeffrey L. Saver, M.D.
Disclosures from all authors are reported in the full text of the NEJM article and on the abstract presented at the International Stroke Conference.
The research described was supported by the National Institutes of Health's National Institute of Neurological Disorders and Stroke (grant number P50 NS044378). Concentric Medical, Inc. (Mountain View, Calif.) provided study catheters and devices from study start until August, 2007; thereafter, costs for all study catheters and devices have been covered by study funds or third party payors.
About Georgetown University Medical Center
Georgetown University Medical Center is an internationally recognized academic medical center with a three-part mission of research, teaching and patient care (through MedStar Health). GUMC's mission is carried out with a strong emphasis on public service and a dedication to the Catholic, Jesuit principle of cura personalis -- or "care of the whole person." The Medical Center includes the School of Medicine and the School of Nursing & Health Studies, both nationally ranked; Georgetown Lombardi Comprehensive Cancer Center, designated as a comprehensive cancer center by the National Cancer Institute; and the Biomedical Graduate Research Organization (BGRO), which accounts for the majority of externally funded research at GUMC including a Clinical Translation and Science Award from the National Institutes of Health. In fiscal year 2010-11, GUMC accounted for 85 percent of the university's sponsored research funding.