MONDAY, April 25, 2005 (HealthDay News) -- A combination of the clot-preventing drug clopidogrel (Plavix) and aspirin was more powerful than aspirin alone in reducing formation of tiny but threatening blood clots in a study of people at very high risk of stroke, European researchers report.
It was a small study for a short duration --107 patients treated for seven days -- but it is a first step on the same path that established the use of the two-drug combination in heart disease, said Dr. Hugh S. Markus. He is lead author of the report, which appears in the April 26 online issue of Circulation, and a professor of neurology at St. George's Hospital Medical School in London.
The study involved 107 participants at 11 medical centers in England, France, Germany and Switzerland. All people in the trial had at least a 50 percent narrowing of the carotid artery, the main blood vessel carrying blood to the brain, and all had suffered either a stroke or a transient ischemic attack -- a "mini-stroke" -- in the previous three months. Aspirin to prevent clot formation is standard treatment for such patients.
A technique called transcranial Doppler ultrasound, which can detect the tiniest of blood clots, showed that such clots formed in only 44 percent of the 51 people who got both clopidogrel and aspirin, compared to 73 percent of the 56 people who got aspirin alone.
Formation of such clots is a warning sign of a potential major stroke, Markus explained, and the trial was designed to show that "by treating these patients more aggressively, we can prevent strokes."
But, Markus added, "we are a long way behind heart disease in many respects" in showing that the aspirin-clopidogrel combination can prevent strokes. Larger studies on a longer time scale will be needed to do that, he said, but "this is the first time ever that the treatment for stroke prevention has been implemented in a multi-center study."
Aspirin and Plavix prevent clots by inhibiting the blood cells called platelets from clumping together. A number of trials have established the role of the combination in heart conditions, said Dr. Marc S. Sabatine, an associate physician in the cardiovascular division of Brigham and Women's Hospital in Boston, and a leader of one such trial.
That trial, the results of which were reported earlier this year, showed that the combined drug treatment reduced the death rate in people who suffered major heart attacks, Sabatine said. Other studies have shown that the drug tandem helps keep arteries open after implantation of stents, metal tubes used after the artery-opening procedure called angioplasty. And the two-drug regimen reduces the death rate by 20 percent in people who suffer smaller heart attacks or have unstable angina, the chest pain that is a major marker of coronary trouble, he said.
Aspirin and Plavix now are given to virtually all people who receive stents, Sabatine said, and the combination is being tested as a long-term preventive therapy for people with less severe heart problems.
It stands to reason that the combination should work against stroke, he said, since the mechanism behind ischemic strokes, caused by blockage of an artery, is the same in the brain as in the heart.
In both cases, trouble begins with the formation of plaque, cholesterol-rich fatty deposits in an artery. A plaque can rupture, activating platelets to form major clots that block the artery.
"Aspirin is good at preventing this, but aspirin does not inhibit all platelet aggregation," Sabatine said. "Clopidogrel works by a different method, so the two are synergistic."
Markus reiterated that longer studies with more participants are needed on the benefits of the two-drug therapy for stroke.
To learn more about stroke, visit the National Institute of Neurological Diseases and Stroke.