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Letter From The Editor
We don’t build each issue of HMI WORLD around a common theme, but sometimes those themes emerge on their own. The theme that jumps out in the November-December 2007 issue is outputs.
Around Harvard
This article originally appeared in the October 2007 Harvard Heart Letter and is provided courtesy of Harvard Health Publications.
Scaling back on antibiotics
Most people, even those with heart disease, don’t need to take antibiotics before a routine dental or surgical procedure.
Since the 1950s, the American Heart Association (AHA) and other medical organizations have urged a sizable group of people to take antibiotics before having dental work, a colonoscopy, or other procedures that might dump bacteria into the bloodstream. A dose of penicillin, so the thinking went, could prevent infective endocarditis, a potentially serious infection of the lining of the heart. After a hard-nosed look at the latest evidence, an expert panel assembled by the AHA puts much more emphasis on taking care of your teeth and limits preprocedure antibiotics to a smaller group.
Infection from within
Infective endocarditis occurs when bacteria or fungi invade the slippery endocardium, the innermost layer of the heart’s chambers. It isn’t common, affecting only about 15,000 Americans a year. But it is potentially deadly, and hard to get rid of. The growing mat of microorganisms can erode heart tissue, making it prone to other infections. It can damage heart valves and lead to heart failure or rhythm problems. If a piece of the growth breaks away and slips into the bloodstream, it can cause a heart attack or stroke.
The organisms that kick off endocarditis tend to come from within. They live on your skin, in your mouth, up your nose, and inside your airways or digestive system. They don’t ordinarily affect the heart because they are usually kept out of the bloodstream, and when they do enter the circulation, they find it tough to latch onto the slick endocardium.
Having a tooth extraction, gum surgery, or other dental work causes a temporary spike in the number of bacteria in the bloodstream (a condition called bacteremia). Experts long assumed that this extra load increases the odds of developing infective endocarditis.
Endocarditis close up
Infective endocarditis arises when bacteria, fungi, and other microbes from the mouth, nose, or skin begin to grow on the inner lining of the heart. Common sites for infection are the mitral valve (through which blood enters the left ventricle) and the aortic valve (through which oxygenated blood flows to the body). Infective endocarditis can erode the valves and cause them to leak, which may then lead to heart failure.
Risks and benefits
Since 1955, the AHA has recommended that people at risk for infective endocarditis take antibiotics before procedures that might release bacteria into the bloodstream. Taking antibiotics as a preventive measure made sense for five reasons:
- Infective endocarditis is dangerous.
- It is far better to prevent endocarditis than to try to treat it.
- Certain conditions seem to increase the chance of infection.
- Dental work and other procedures increase the amount of bacteria and fungi in the bloodstream.
- Antibiotics should prevent these critters from setting up housekeeping in the heart.
Number five has been called into question over the last few years. Although there’s no doubt that scraping plaque from teeth, planing gums, or pulling a tooth lets microbes from the mouth flood the bloodstream, some studies show that chewing food, brushing teeth, flossing, and even using a toothpick do the same thing. Over the course of a year, these daily activities allow far more bacteria to enter the bloodstream than does the occasional dental procedure. By one estimate, your exposure to bacteremia from brushing your teeth twice a day for a year is 154,000 times higher than it is from having a tooth pulled.
No large trials have tested whether taking antibiotics before dental work truly prevents endocarditis. If it does, the effect is so small that hundreds of people would need to take antibiotics to prevent a single case of infective endocarditis.
Why not take antibiotics “just in case”? Because there are side effects to consider. Antibiotics can cause rashes and diarrhea. They can upset the stomach. Sometimes they are deadly — for every million people who take penicillin, as many as 25 die from an allergic reaction. And a growing number of microorganisms are developing resistance to antibiotics.
Given these drawbacks, antibiotic therapy for all would cause more harm than good.
Fewer need antibiotics
In light of the evidence, the AHA recommends preemptory antibiotics only for people at greatest danger from infective endocarditis (see “Who needs antibiotics before dental work?”). They aren’t needed for all types of dentistry, and they aren’t needed for colonoscopies or other routine gastrointestinal procedures, either.
Who needs antibiotics before dental work?
The American Heart Association panel recommends taking antibiotics before dental work or a procedure on the nose, lungs, or infected skin or muscle only if you have an artificial heart valve (biological or mechanical), you’ve had infective endocarditis before, you have a congenital heart disease that has not yet been repaired, that was fixed with a device or artificial material, or that was fixed but still causes some problems, or you’ve received a heart transplant and have developed a valve problem.
Antibiotics are needed only before a procedure in which the gums or teeth are poked, prodded, or pulled, or in which the gums or skin of the mouth might be broken. This includes tooth extraction, teeth cleaning, gum planing, and similar procedures.
Antibiotics aren’t needed before dental x-rays, the placement or adjustment of braces, bridges, or dentures, or other procedures that aren’t likely to break the skin.
These changes mean that many people who, under the old guidelines, were urged to take antibiotics before dental work no longer need them. You no longer need to take pre-dentistry antibiotics if you have mitral valve prolapse or another valve disease, rheumatic heart disease, a defect in the septum (the wall separating the two sides of the heart), hypertrophic cardiomyopathy, or other forms of heart disease.
Sticking with the theme of “prevention is more important than treatment,” the AHA panel emphasized the importance of routine oral health. Brushing teeth and flossing, along with regular visits to the dentist, limit the growth of bacteria in the mouth and the inflammation that allows them to get into the bloodstream. This appears to be a better way to prevent endocarditis than taking antibiotics before a dental procedure.
