Advances in thrombolysis
March 21, 2011
Washington State has one of the highest stroke mortality rates in the nation. To improve this situation, acute interventional therapies for stroke are being employed to restore circulation to ischemic brain tissue that surrounds areas of completed infraction, while avoiding risk of hemorrhage due to reperfusion of large areas of infracted brain tissue.
Urgent thrombolysis with intravenous alteplase is the only therapy known to improve clinical outcomes following acute stroke. Unfortunately, alteplase has had limited usage because many patients arrive in an emergency department after the three-hour treatment window. The FDA has also approved two clot removal devices based on the ability to restore circulation. These devices are used up to eight hours after symptom onset. Several approaches to improved acute stroke care are now under way, including extension of the thrombolysis window to 4.5 hours, identification of safer thrombolytic agents and research identifying brain at risk of infarction following a stroke.
A recent European study demonstrated the efficacy of alteplase up to 4.5 hours after ischemic stroke in patients younger than age 80 years who have neither diabetes mellitus or prior stroke. The safety profile during this longer window for these patients appears similar to that at three hours.
Another promising advance employs a new thrombolytic agent called desmoteplase. Derived from the saliva of the vampire bat, this agent has a longer half life than alteplase and does not break down basement membranes, leading to a lower risk of hemorrhagic complications. The Swedish Stroke Program is part of an international effort to test this drug in a nine-hour window.
Todd Czartoski, M.D., and Bart Keogh, M.D., Ph.D., are collaborating with the stroke team at Stanford University to identify patients with viable ischemic tissue regardless of time from onset of symptoms. Perfusion MRI identifies impaired blood flow in brain (the “penumbra”) surrounding an infarct. In cases where there is a large area at risk, the use of alteplase or clot retrieval may prove beneficial long after the three-hour window has elapsed.
Telestroke is another important development in acute stroke care. This program enables the timely alteplase treatment of patients in emergency rooms around the Pacific Northwest that lack onsite neurological expertise.
For more information about the Swedish Stroke Program, contact Sherene Schlegel, R.N., FAHA, at 206-320-3484. For information about telestroke, contact Tammy Cress, R.N., MSN, at 206-320-3112.