Doctors at Washington University School of Medicine in St. Louis found that the surgery, which reduces risk of additional strokes, should be delayed if patients were recently treated with the clot-busting drug tPA.
"Patients undergoing this surgery a few days after tPA treatment were at higher risk for bleeding complications," said author Greg Zipfel, MD, an associate professor of neurological surgery who treats patients at Barnes-Jewish Hospital. "We think delaying the procedure by at least one week after tPA treatment likely will make the procedure safer and improve patient outcomes."
The study appears online in the journal Neurosurgery.
Symptoms of stroke include dizziness, paralysis, confusion, loss of sight, numbness, weakness and trouble speaking. After symptoms start, doctors have 4.5 hours to confirm that a stroke is occurring and to give patients tPA to break up the blood clots causing the strokes. (Until recently, the time limit for tPA administration was three hours after stroke onset.)
After the stroke, physicians scan the carotid arteries, the two large blood vessels in the neck that provide much of the brain's blood supply. If one of these arteries is more than 50 percent blocked with fatty deposits called plaque, doctors commonly recommend surgical removal of the plaque a few days after the stroke.
During this procedure, known as a carotid endarterectomy, surgeons open the diseased artery and remove the plaque. This helps reduce the chances that a fragment of the plaque will break free, block a small brain blood vessel and cause another stroke.
First author Ananth Vellimana, MD, a second-year neurosurgery resident at Barnes-Jewish Hospital, analyzed outcomes in 142 patients who underwent the procedure at the hospital from 1995 to 2007. Eleven patients received the procedure a few days after a stroke and tPA treatment; 131 had surgery after suffering a stroke or stroke-like symptoms but did not receive tPA treatment.
Two cases of brain bleeding occurred in the much smaller group of patients who had the surgery within a few days of tPA treatment, but only one case occurred in the larger group, which had not been treated with tPA.
"Treatment with tPA appears to affect the risk of brain bleeding after surgery, but the body clears tPA much too rapidly for it to be the direct cause of the problem," Vellimana noted. "One possibility is that tPA's suppression of blood clotting during stroke treatment may cause microhemorrhages in the brain. These small bleeds could become significantly bigger after an endarterectomy increases blood flow to the brain."
Advanced imaging techniques may allow physicians to detect these microhemorrhages and better assess the risks of the surgery, according to Vellimana. If patients exhibit these small bleeds, doctors may delay the procedure further to give the blood vessels a chance to heal.
Treatment with tPA also could be activating a molecular chain reaction that temporarily increases the likelihood of bleeding in the brain. As an example, the researchers noted that tPA boosts production of a protein that increases the risk of bleeding.
"These two forms of treatment - tPA and endarterectomy - each have proven value in limiting or preventing brain damage from strokes," said Zipfel. "The challenge now is determining how to time the use of these treatments to maximize benefit and minimize risk."
This study was supported by National Institutes of Health (NIH) grants: NINDS P50 NS055977 (C.P.D., G.J.Z.), NINDS U01 NS58728 (C.P.D.), and NINDS R01 NS051631 (C.P.D).
Vellimana AK, Yarbrough CK, Blackburn S, Strom RG, Pilgram TK, Lee J-M, Grubb Jr. RL, Rich KM, Chicoine MR, Dacey Jr. RG, Derdeyn CP, Zipfel GJ. Intravenous tPA therapy is an independent risk factor for symptomatic intracerebral hemorrhage following carotid endarterectomy. Neurosurgery, published online Feb. 18.
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