DALLAS, March 3 -- By adding up "point" totals assigned to certain risk factors, doctors can arrive at a "tragic number" which can help predict which heart attack patients may be at immediate risk of a stroke.
In research published in today's Circulation: Journal of the American Heart Association, scientists say they've developed a simple chart which assigns "point" totals to six different risk factors. The chart was created to help determine the risk of ischemic stroke -- the most common kind of stroke, which is caused by a blockage of blood flow to the brain -- in patients whose heart attacks were treated with thrombolytic, or clot-busting, therapy.
With this chart, which the scientists call a "nomogram," high point totals equal high risk for stroke. For example, a patient with a point total of 67 has a 0.5 percent risk of ischemic stroke, while an individual whose total is 162 has a 35 percent risk of stroke.
"The beauty of the chart it is that it's easy to use," says the study's lead author Kenneth Mahaffey, M.D., assistant professor of medicine at Duke University Medical Center, Durham, N.C. "It can be put on a pocket card, and you really only need to have six clinical characteristics. By going through those, you put together the point total and determine the risk. It gives physicians an immediate baseline risk assessment for each individual patient."
Ischemic strokes now occur in 0.1 to 1.3 percent of heart attack patients treated with clot-busting drugs. About 25 percent of the 1.1 million Americans who each year have a heart attack are treated with these drugs.
Researchers hope that the chart will better identify the approximately 3500 heart attack survivors each year who are at risk for developing stroke after their heart attacks.
"The percent figures may seem small, but when you look at the number of heart attacks that happen each year, this becomes a very important medical issue not only in this country, but around the world," says Mahaffey. "Patients who have a nonhemorrhagic stroke after a heart attack often do so in the hospital and then you're looking at 20 percent of that group dying, and 50-60 percent of the rest having significant disability. This needs to be addressed."
To determine the risk factors that were most predictive of a stroke, the researchers studied 247 people whose heart attacks were treated by clot-busting drugs and who subsequently suffered a stroke. The heart attack patients were randomly assigned to one of four clot-busting regimens within six hours of having a heart attack.
The chart is made up of three parts. The first part assigns point totals to six risk factors - older age, fast heart rate, diabetes, high blood pressure, previous cardiovascular disease and previous chest pain. In the second part, the points are totaled and then can be referred to the third portion which is a chart equating points to increased risk.
In an example of how the nomogram works, a 71-year old nondiabetic patient with previous cardiovascular disease, a history of high blood pressure and previous chest pain who arrives at the hospital with a heart rate of 121 beats per minute would have a total score of 128, which equals a 10 percent probability of having an in-hospital nonhemorragic stroke.
Study co-authors are Christopher B. Granger, M.D.; Michael A. Sloan, M.D.; Trevor D. Thompson, B.S.; Joel M. Gore, M.D.; W. Douglas Weaver, M.D.; Harvey D. White, M.B, D.Sc; Maarten L. Simoons, M.D.; Gabriel I. Barbash, M.D., MPH; Eric J. Topol, M.D. and Robert M. Califf, M.D.
Media advisory: Dr. Mahaffey can be contacted by phone at (919) 286-8700. (Please do not publish number.)