Infection as a risk factor for infarction and atherosclerosis.

A growing amount of clinical and experimental evidence suggests a link between infection and atherosclerotic diseases including both myocardial and cerebral infarction. A prime example is a greatly increased risk of stroke in septicaemic patients with and without endocarditis. Controlled clinical studies have recently shown, however, that certain other milder bacterial infections are also a risk factor for infarction. A preceding febrile respiratory infection was a major risk factor for stroke in young and middle aged patients. In patients with acute myocardial infarction Chlamydia pneumoniae and dental infections seem to be risk factors according to one controlled clinical study. Several possible mechanisms could explain the observed association of infection and infarction. For instance, infection causes a hypercoagulable state which increases the risk of thrombosis. In addition, infection has profound and harmful effects on prostaglandin and lipid metabolism. Infection may also have some role in the atherosclerotic process itself by inducing damage and inflammation in vascular endothelium in the presence of hypercholesterolemia. So far, however, little clinical evidence is available to suggest that by controlling infection the risk of infarction or development of atherosclerotic lesions might be reduced except in patients with endocarditis, where the risk of thromboembolic complications rapidly diminished when the infection is controlled with antimicrobial therapy.