The clot-busting drug tPA (short for tissue plasminogen activator) is the gold standard for treating acute ischemic stroke, but only if it's administered to the patient intravenously within three, or sometimes 4.5, hours of the onset of stroke symptoms—a very tight window. Injecting tPA through the artery directly to the clot, alongside new endovascular devices to directly remove the clot are complementary treatments that are being used in specialized stroke centers to improve the chances of dissolving blood clots and to buy patients valuable time.
“Three to four and half hours is a very limited amount of time, and many patients do not arrive to the hospital within this time window. In addition, intravenous tPA may not dissolve the clot rapidly enough in all patients” says Dr. Magdy Selim, Chief of the division of stroke and cerebrovascular disease at Beth Israel Deaconess Medical Center’s Stroke Center and an Associate Professor of Neurology at Harvard Medical School. “But with intra-arterial tPA and recent clot removal devices, we can improve the chances for busting the clot.” This is a work in progress and may not be suitable for all stroke patients. We have learned that selecting the appropriate patients who are likely to benefit from these advanced treatments and avoiding delays to start these interventions as soon as possible are essential to achieve good results.
According to the American Stroke Association, about 795,000 people experience a new or recurrent stroke each year, and 150,000 of them will die. Stroke is the number-four cause of death in the U.S., and a leading cause of serious, long-term disability. On average, every 40 seconds, someone in the United States has a stroke and dies of one approximately every 4 minutes.
A stroke occurs when part of the brain is deprived of its blood supply, either due to a clot blocking the artery or due to bleeding. tPA is effective for treating the strokes caused by clots, called ischemic strokes, which account for about 80 percent of all strokes.
“Right now, the standard of care is to give intravenous tPA if a patient arrives in the emergency room within three hours of experiencing stroke symptoms, and has no contraindications to tPA use, such as recent major surgery or active bleeding." “But a lot of people don’t get to the hospital within three or 4.5 hours. Often, if the patient doesn’t realize they’re having a stroke, they delay getting to the hospital.”
Some patients aren’t candidates for the intravenous form of the drug. A patient who recently underwent a major surgery, for example, can’t receive tPA intravenously because of concerns about the risk of bleeding from the surgical site. When tPA is delivered via the artery or a clot removal device is used, however, this is less of an issue.
In the intra-arterial tPA and clot removal procedures, the physician inserts a thin, flexible catheter into an artery (usually in the groin area) and steers it up to the area of the clot. The tPA is then administered through the catheter to the clot, dissolving it, and a small device might be used to pull out the clot. It is important to note that tPA cannot be used to treat hemorrhagic strokes, which occur when a blood vessel ruptures, leaking blood into the brain.
While still considered experimental, intra-arterial tPA and endovascular clot removal is an accepted form of treatment for some patients at most stroke centers. However, every hospital is not equipped to offer it; some community hospitals, for example, don’t have the necessary staff available around-the-clock to do the procedure. Often these hospitals will administer intravenous tPA, then transport the patient to a comprehensive stroke center for additional treatment as needed.
Patients must remember, however, that the only way to benefit from these therapies is to get to a hospital immediately if a stroke is suspected. “Dial 9-1-1 immediately, don’t wait to see if it will get better,” advises Dr. Selim. “The sooner a person gets to the hospital, the better the chance they will recover.”
To contact the Stroke Center at Beth Israel Deaconess Medical Center, call 617-632-8913.