Physicians in Houston and three other centers used a hand-held extracranial ultrasound device to target stroke-causing blood clots during the pilot study. The sound waves are believed to seek out the clot and deliver a heavy dose of the clot-busting drug tPA to and through it, relieving the obstruction to blood flow and helping the brain heal. All of the patients also received the clot-busting tPA, and their results were compared with 63 other patients who received tPA alone.
Andrei Alexandrov, M.D., assistant professor of neurology at the UT Medical School, initially used the ultrasound device to track the efficacy of tPA, the only approved drug for treating blood clots in stroke victims. However, emergency room nurses began telling him that patients who had been monitored in this way were recovering faster than those he had not monitored. Alexandrov began a pilot study to determine whether the ultrasound itself had therapeutic uses.
"We had 126 patients enrolled in the study, with an average age of 70," Alexandrov said. "Thirty-eight percent of the patients on whom I used ultrasound sustained a complete clearance of their clots within two hours (compared to 12 percent of the patients receiving tPA alone), and over 70 percent experienced a complete or partial clearance."
Alexandrov fitted the patients with a frame similar to the protective framework inside a hard hat and then used a Food and Drug Administration-approved diagnostic frequency setting of two megahertz to single out blood clots in the brain while tPA was administered.
"This frequency is fast but gentle, safe to use and efficacious. It creates micro-vibrations that work on the surface of the clot to open up a larger surface that the tPA can then bind to and penetrate," he said.
In addition to killing more than 167,000 Americans a year, strokes permanently disable many victims, making it the top cause of disability in the nation. Optimum stroke care is often difficult to obtain outside of major trauma centers.
An abstract of the study is available upon request.
Journal
New England Journal of Medicine