In as many as one in five people over age 55, when the heart contracts to send blood around the body, some degree of backward leakage occurs across the mitral valve, a condition known as mitral regurgitation (MR). When sufficiently severe, MR causes buildup of blood in the lungs, leading to difficulty in breathing (dyspnea, or "shortness of breath"), a serious condition called congestive heart failure. MR also can cause heart rhythm irregularities (arrhythmias) such as atrial fibrillation, which can lead to strokes and other problems, and ventricular tachycardia, which can cause sudden death.
A new study finds that monitoring the capacity of these patients to exercise on a treadmill—an evaluation called exercise tolerance testing (ETT)—may be useful in predicting the condition's progression and whether the patient will need surgery. Led by NewYork-Presbyterian Hospital/Weill Cornell Medical Center, the research is published in the American Journal of Cardiology.
"Mitral regurgitation can be very benign, going unnoticed for many years, or can be severe, impeding the heart's proper function and leading to complications, even death. There are few accurate ways to predict the seriousness of a single case, and these methods require fairly sophisticated and expensive imaging. Our study shows that exercise tolerance testing, a simple procedure often performed in doctors' offices, is an excellent tool for predicting if the patient is deteriorating and needs surgery," says Dr. Jeffrey S. Borer, a study co-author ; director of the Howard Gilman Institute for Valvular Heart Diseases at NewYork-Presbyterian/Weill Cornell; and the Gladys and Roland Harriman Professor of Cardiovascular Medicine and professor of cardiovascular medicine in cardiothoracic surgery at Weill Cornell Medical College.
"We found that exercise testing is a simple and relatively inexpensive way to predict outcomes. Patients with mitral regurgitation who perform well on the treadmill will likely remain healthy and not have to undergo further testing for a number of years. This gives these patients peace of mind," says principal investigator Dr. Phyllis G. Supino, associate research professor of public health in medicine and associate research professor of public health at Weill Cornell Medical College.
Developed in its most simple form in the 1920s, exercise tolerance testing (ETT) is used commonly to assess the progression of coronary artery disease and the severity of aortic stenosis.
In mitral regurgitation, the mitral valve does not close completely, as it should, when the heart contracts, allowing blood to flow backward instead of forward, limiting blood flow to the body. Symptoms include shortness of breath, fatigue, cough, heart palpitations, swollen feet or ankles, and excessive urination. A characteristic heart murmur can be heard with a stethoscope.
In the current study, researchers followed 38 patients with chronic severe nonischemic MR (that is, MR not due to a prior heart attack) for an average of seven years. All underwent ETT at study entry. Patients who could continue exercising for 15 minutes or longer (of a maximum total of 18 minutes) had a fivefold lower annual risk of developing heart failure or other evidence of severe heart dysfunction necessitating surgery, compared to patients who were unable to exercise for that length of time.
In patients with chronic severe nonischemic MR, progression to surgical indications generally is rapid. There are two surgical options for the treatment of MR: mitral valve replacement and mitral valve repair.
The study was co-led by Dr. Borer and Dr. Supino. Co-authors included Drs. Clare Hochreiter, Paul Kligfield, Edmund M. Herrold and Jacek J. Preibisz—all of Weill Cornell Medical College; Dr. Anuj Gupta, now at Columbia; and Dr. Karlheinz Schuleri, now at Johns Hopkins University.
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