Medical Edge Newspaper Column

Preventing Endocarditis: Where Antibiotics Need Not Apply

June 17, 2007
Dear Mayo Clinic:
A few years ago, I was diagnosed with mitral valve prolapse and was told I should always take antibiotics before dental procedures to protect against bacterial endocarditis. My dentist in fact feels that antibiotics are necessary. But some doctors who do even more invasive procedures apparently feel different. During my last couple of colonoscopies my physician said I didn't need antibiotics and didn't give me any. What are the real risks for someone like me? Is it different for dental vs. other invasive procedures? — East Setauket, N.Y.

Answer:
Mitral valve prolapse (MVP) occurs when the valve between one of the heart's upper chambers (left atrium) and the adjacent lower chamber (left ventricle) doesn't close properly, often because the valve's flaps are oversized or thickened. When the ventricle contracts, the flaps prolapse , or bulge. MVP sometimes leads to mitral valve regurgitation, a condition in which blood leaks backward into the atrium.

A patient with MVP is at increased risk of endocarditis — an infection of the thin membrane, called the endocardium, that surrounds the heart's four valves and lines its four chambers. This infection typically occurs when bacteria from parts of the body, such as the mouth, spread through the bloodstream and attach themselves to an area of the heart — an abnormal mitral valve, for example — that is especially hospitable because of the turbulent blood flow produced in its vicinity. This turbulence makes blood platelets build up on the valve, creating a harbor for bacteria that in turn may grow to critical levels.

If left untreated, endocarditis would damage the valves and permanently destroy the membrane, leading to heart failure and death.

Given the seriousness of endocarditis, physicians and dentists have traditionally been conservative. When people with MVP and certain other conditions underwent procedures such as tooth extractions, surgeries, or invasive practices like colonoscopies, they were advised to take antibiotics to prevent endocarditis and its attendant woes.

But recently, the American Heart Association issued new guidelines that curtailed the practice of giving prophylactic antibiotics. As a member of the committee that formulated these guidelines, which we worked on for years, I can tell you from firsthand experience why we made them.

For one thing, there is no evidence that the prophylactic antibiotics given before dental or other procedures are actually effective. For another, we concluded that the risk of endocarditis, though not high in absolute terms, is much greater from everyday activities, such as chewing your food or brushing your teeth, than from a single visit to the dentist for a tooth extraction or cleaning.

The data that led to this conclusion are impressive. For example, over the course of a year, the total number of minutes of exposure to bacteremia (the presence of bacteria in the blood) from twice-daily tooth brushing is some 154,000 times greater than from having a tooth pulled. Given that we don't recommend antibiotics in conjunction with tooth brushing, it makes no sense to recommend them for an infrequent event. Even if prophylaxis for a dental procedure were 100 percent effective, it would only prevent an exceedingly small number of cases.

Yet another reason is that prophylaxis has its own risks. Antibiotics can cause gastrointestinal disturbances, and can sometimes provoke acute allergic reactions, even anaphylaxis and death.

We did retain the antibiotic-prophylaxis recommendation for some dental procedures, but only for certain individuals — such as patients with artificial heart valves or certain congenital heart defects (not including MVP) — who have a high risk of bad outcomes should they get endocarditis.

We also recommend common-sense practices, such as seeing your dentist on a regular basis and maintaining good daily oral hygiene. This reduces your risk of cavities and gingivitis, which lowers the risk of bacteremia from daily events such as toothbrushing and chewing, which in turn reduces the chance of getting endocarditis. Similarly, maintaining good hygiene should apply to the whole body. If, for instance, you have an infected wound, such as a cut that develops into an abscess, it's important to see your doctor.

— Walter R. Wilson, M.D., Infectious Diseases, Mayo Clinic, Rochester, Minn.