Heart Attacks Caused by Infections?

(December 26, 1997) - The way a heart attack (myocardial infarction) comes about is clear. It involves the death of part of the heart muscle (myocardium) due to blockage of a coronary artery delivering nutrients and oxygen to the myocardium. Blockage of the coronary artery is commonly caused by a clot that forms on the inner wall of the artery at the site of damage by atherosclerosis, the accumulation of cholesterol deposits on the walls of the artery. These cholesterol deposits cause hardening and thickening of artery walls and narrowing of their interior diameter.

Some of the risk factors for atherosclerosis and heart attacks are also quite well known. They include a high blood cholesterol (especially, an elevated level of the "bad" LDL cholesterol), high blood pressure (hypertension), diabetes mellitus, cigarette smoking, and a family history of coronary artery disease. There is considerable evidence that an elevated blood level of the amino acid homocysteine may be a risk factor, too.

Not infrequently, however, advanced atherosclerosis is found in the coronary arteries of people with no known added risk factor. Given the absence of a obvious culprit, scientists are examining some new suspects. One of these is infection.

The concept is that certain chronic (long-term) infections may trigger atherosclerosis -- or they may at the least aggravate it -- and lead to heart attacks. In this regard, Drs. Sandeep Gupta and John Camm from St George's Hospital Medical School in London have weighed the available scientific data associating infections with the development of atherosclerosis and coronary heart disease. Their comprehensive review was published in the periodical Clinical Cardiology (vol. 20, pages 829-836,1997).