Exercise May Fatally Rupture Artery Plaque Of Sedentary Men With Heart Disease And High Cholesterol

November 10, 1997

ORLANDO, Nov. 10 -- For people with heart disease and high blood levels of cholesterol, heavy exertion -- even mowing the lawn -- may trigger a sudden heart attack by rupturing the plaque obstructing the arteries of the heart, according to a study presented today at the American Heart Association's 70th Scientific Sessions.

For some time scientists have known that exercise can trigger a heart attack or chest pain in people with heart disease, says Renu Virmani, M.D., chairperson of the Department of Cardiovascular Pathology at the Armed Forces Institute of Pathology in Washington, D.C.

"There is a lot of evidence that people with serious heart disease who are out of shape have a higher risk of sudden coronary death if they engage in rigorous activity. What we have seen in this study is the actual mechanism behind exertion-associated deaths among men with coronary heart disease and high cholesterol," says Virmani.

"We have found physical differences in the coronary arteries of 102 sedentary men with heart disease and high cholesterol who died during normal daily activities compared to 26 who were engaged in some strenuous activity, such as moving furniture, mowing the lawn or shoveling snow. In sedentary men who exerted themselves, we found blood clots in plaque that had burst." Blood clots, created when cholesterol-filled plaque in blood vessels rupture or break open, plug the blood vessel, obstructing blood to the heart. A heart attack results.

Even among men not exerting themselves, blood clots formed on cholesterol-filled plaque, which had not ruptured.

Most of the men were in their 50s and about half were smokers.

Among those who died during exercise, 62 percent showed evidence of ruptured plaque compared to just 28 percent of men who died during normal daily activities or while resting. The men who died during exercise also had higher total cholesterol levels independent of other risk factors -- and more "vulnerable" plaque and actual plaque rupture, Virmani says.

Plaque is vulnerable to rupture when it has a thin, fibrous cap filled with macrophages, large immune system cells that surround and absorb foreign substances in the body. When a plaque ruptures, it bleeds just as an unhealed skin scab might, and its fatty core extrudes into the artery.

Sedentary men with coronary heart disease and hypercholesterolemia -- significantly elevated levels of cholesterol in the bloodstream that can lead to the build-up of plaque on artery walls -- must be especially cautious about undertaking any vigorous physical activity while levels are too high, she says.

Men with coronary heart disease and total cholesterol higher than 210 mg/dl -- especially those with higher low-density lipoprotein (LDL) levels -- should always be advised by physicians to lower their cholesterol before starting any kind of exercise program, according to Virmani.

Co-authors are by Gray T. Malcolm, M.D., of Louisiana State University in New Orleans, and Andrew Farb, M.D., and Allen P. Burke, M.D., also of the Armed Forces Institute of Pathology.

American Heart Association

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