INFECTION CONTROL: Heart Attacks, Coronary Artery Disease (CAD) and Bacteria

by R.A. Clappison, DDS, FRCD(C)

Theory has it that inflammation produced by low-grade chronic infections can play a major part in CAD (coronary artery disease). Inflammation, we know, produces a response by the immune system which in this case can be detrimental in that these mobilized cells injure the frail lining of blood vessels by secreting chemicals that stimulate the growth of arterial plaques.

A 1997 Harvard University study observed over six years that men with higher C-reactive protein (CRP) released during inflammation had three times as many heart attacks as those men with the lowest levels. Of interest also was the fact that the reduction of heart attack risk conferred by aspirin was related directly to individual CRP levels. Aspirin reduced the heart attack risk in those with the highest CRP levels. Those that take low-strength aspirin take it mostly because they feel that it inhibits blood clot formation but this study surmises that aspirin adds to this protection by the addition of its anti-inflammatory property.

Contemporary studies report that Chlamydia pneumoniae has a role in CAD. Helicobacter pylori, a bacterium associated with many gastric ulcers, is another causative organism associated with CAD. More than one half of American adults have antibodies to C Pneumoniae and H. Pylori showing a prior infection with these organisms The infectious factors associated with periodontal disease have also been implicated.- all the more reason to educate patients about the benefits of routine flossing.

Antibiotics, such as azithromycin, have been used in studies in rabbits regularly infected with C. pneumoniae where it was shown to slow the progress of atherosclerosis. This may not have the same effect in people. Antibiotics used in two small studies on people with CAD reduced the rate of a second episode and a study published last winter in the journal of the American Medical Association suggests that certain antibiotics may prevent heart attacks. This study involved 3,315 patients with first-time heart attacks and 13,139 people who had never experienced a heart attack. Those treated with antibiotics proven to be effective against C. pneumoniae had a reduction in risk and in some cases – more than 50 per cent. There are concerns about this study that it was observational and that antibodies were not measured. Concern is also expressed that the results were not entirely due to the antibiotics but to some other pharmacologic effects.

Patients and the general public should not be rushing off to the physician for antibiotic therapy for CAD since the over-utilization of antibiotics is already creating multiple problems such as untreatable infections. However these studies may be a stepping stone to great benefits.

In the meantime the proven requirements to reduce CAD should be followed such as exercise; reduced cholesterol; diabetic control; weight control; cessation of smoking and control of blood pressure. To this list perhaps we could add better control or elimination of periodontal disease in ourselves and our patients.

* The Johns Hopkins Medical Letter, September 1999