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Too much noise about this heart murmur?

A heart condition called mitral valve prolapse has often been misdiagnosed — especially in women — says Dr. Judith Reichman.

Q: My doctor heard a heart murmur and said I might have mitral valve prolapse. He told me a little about this. Could you give me a fuller explanation? Thank you.

A: First, I would like to you pay attention to the “might” in your doctor’s diagnosis. You may indeed have this condition, but until your doctor does further testing, don’t conclude that you do — it could adversely affect your health. Mitral valve prolapse, or MVP, has been greatly over-diagnosed.

Here is a quick lesson in cardiac physiology to help you understand the mitral valve:

The heart, which contracts about 100,000 times a day, has four chambers. The upper chambers, the atriums, receive and collect blood. The lower chambers, the ventricles, pump the blood throughout the body.

The mitral valve separates the left atrium (which receives oxygenated blood from the lungs) from the left ventricle (which pumps this blood out to the body).

When your heart is functioning properly, the mitral valve opens at just the right time to let the blood flow from the atrium to the ventricle.

This one-way valve contains small flaps, which are like little fingers. If these flaps flop in the wrong direction, some of the blood might not pass through smoothly, or might even regurgitate, or leak. This is called mitral valve prolapse.

Doctors used to think that up to a third of the population had mitral valve prolapse, and it was especially common in young women. When they listened with a stethoscope and heard a certain type of murmur (a “whoosh” after the first heart thump or a “click” between thumps), they diagnosed mitral valve prolapse.

Improved tests, however, have led cardiologists to the conclusion that the mitral valve has normal variations and that a “whoosh” or a “click” does not necessarily mean a heart condition.

Even if the valve doesn’t close perfectly, if there is no leak, it will not cause clinical problems. If, however, there is a leak and the blood flow is not unidirectional, it can lead to a host of problems, ranging from fainting to heart failure.

A few years ago, in an article in the New England Journal of Medicine, researchers showed that true mitral valve prolapse occurred in only 2.4 percent of the population studied, and that young women were no more likely to have it than anyone else.

To confirm the diagnosis, you must undergo a two-dimensional echocardiogram, an ultrasound of the heart, that shows there is a leak as well as significant abnormality in how the leaflets close.

If mitral valve prolapse resulting in regurgitation is confirmed, you should be followed by a cardiologist in case it worsens and requires some form of intervention.

You should also take an antibiotic, such as amoxicillin, ampicillin, penicillin or cephalosporin an hour before seeing the dentist. This is because the mouth contains more microbes than any part of the body, so teeth cleaning and other dental procedures often unleash bacteria into the bloodstream. These bacteria can cling to the flaps of the mitral valve, causing infection. This condition, called bacterial endocarditis, is rare but extremely serious. If it is not controlled with massive intravenous antibiotics, it can result in heart failure and death.

So, if you know you have mitral valve prolapse that causes a leak, which is termed “moderate MVP,” tell your dentist. The American Heart Association says that if no leak has been demonstrated, you are at no greater risk for endocarditis then the average individual and you don’t need antibiotics. A dentist or medical practitioner can prescribe the antibiotics you need before your visit. You also need prophylactic antibiotics for any other invasive surgery that can make bacteria enter the bloodstream.

Dr. Reichman’s Bottom Line: Mitral valve prolapse is not nearly as common as we once believed. A doctor can confirm the diagnosis with an echocardiogram so you know whether to take antibiotics before visiting the dentist or having surgery.

Dr. Judith Reichman, the “Today” show's medical contributor on women's health, has practiced obstetrics and gynecology for more than 20 years. You will find many answers to your questions in her latest book, "Slow Your Clock Down: The Complete Guide to a Healthy, Younger You," published by William Morrow, a division of .

PLEASE NOTE: The information in this column should not be construed as providing specific medical advice, but rather to offer readers information to better understand their lives and health. It is not intended to provide an alternative to professional treatment or to replace the services of a physician.