Heart attack survivors may be at greater risk for a second coronary or other adverse cardiac problems if blood tests show evidence of infection with a form of chlamydia. They may have a more than four times greater risk for a fatal or nonfatal heart attack and unstable angina (chest pains while resting). But, taking a "short-course" of antibiotics seems to lower these risks dramatically.

The findings show that an infection can be important in heart attacks, but one has to look at these results as you would smoking and heart disease. This means not all people who have infections of this kind develop heart attacks. Heart attack is very complex and many variables play a role. But I think this is a step forward in the understanding that infections -- - this one and maybe others -- may play a role. It's no more than a factor, not the total picture.

Laboratory studies have implicated immature white blood cells called monocytes in the formation of blood clots that can ultimately block an artery already narrowed by heart disease, causing a heart attack. By taking on Chlamydia, monocytes might trigger it to produce a clot-promoting substance called tissue factor.

Circulation (1997;96:404-407)