Heart Valve Problem Not As Serious As Previously Thought

By Amy Norton, Medical Tribune News Service

A type of heart-valve defect that has been linked to serious complications is less common and less severe than the medical world has thought, according to two reports.

Only a small portion of the general population suffers from mitral-valve prolapse, and the condition is more benign than previous research has suggested, researchers reported in Thursday's issue of The New England Journal of Medicine.

Looking at more than 1,600 men and women involved in a government heart-health study, researchers found that just 2.4 percent had mitral-valve prolapse -- far fewer than estimates from past studies that suggested 5 percent to 35 percent of Americans have the condition. The study was led by Dr. Emelia J. Benjamin, an associate professor of medicine at Boston University School of Medicine.

In a second study, Boston researchers found that mitral-valve prolapse was no more common among 213 young stroke victims than among 263 subjects with healthy hearts -- contradicting previous studies that have linked the two conditions in patients age 45 and younger. Dr. Robert A. Levine, an associate professor of medicine at Harvard Medical School, led the study.

Mitral-valve prolapse occurs when the valve that regulates blood flow from the heart's left atrium to the left ventricle sinks from its normal position. Normally, the mitral valve shuts when the heart contracts; a prolapsed valve may fail to close properly, allowing some blood to flow back through the valve, sometimes causing a murmer. A condition called mitral regurgitation may develop, and this sometimes requires repair or replacement of the valve.

But in the Boston University study, few patients with mitral-valve prolapse experienced severe mitral regurgitation, the most common complication of prolapse. Just 7 percent of patients with ``classic'' prolapse suffered regurgitation, and none with the ``non-classic'' form did. In contrast to some past studies, the rates of heart failure and other heart disease were no higher among prolapse patients than controls.

Previous reports of a much higher prevalence of prolapse largely came from hospital-based studies -- an imperfect way to measure its frequency in the general public. In the 1970s and 1980s, Benjamin noted, mitral-valve prolapse appeared to be epidemic, often being diagnosed in otherwise healthy young people -- particularly women -- who had unexplained chest pain or heart palpitations.

But after mitral-valve prolapse was first recognized in the late 1960s, the ensuing prolapse ``fad,'' Benjamin explained, was largely due to physicians' ``enthusiasm for making the diagnosis.'' She noted that in her team's study the condition was no more common among women than men.

In the 1980s, the condition was linked to stroke in younger patients when some studies showed a high prevalence of prolapse among stroke victims 45 and younger. One study of young stroke patients revealed that 40 percent had mitral-valve prolapse.

In both current reports, however, the researchers noted that improved, two-dimensional imaging of the heart allowed them to more accurately discern mitral-valve prolapse, compared with these past studies.

Doctors have in recent years gained a better understanding of the mitral valve itself, Benjamin noted.

``We now know that the valve is saddle-shaped,'' she said, adding that this knowledge has perfected the way in which echocardiographers interpret heart images.

``The brain attached to the machine knows more,'' said Levine, who led the stroke study.

Using diagnostic criteria updated from the early studies of stroke and mitral-valve prolapse, Levine's team found ``no evidence of an association.''

In fact, prolapse was slightly more common among subjects who did not suffer a stroke -- 2.7 percent had the condition, compared with 1.9 percent among stroke patients. Instead, Levine said, most of the stroke patients had other risk factors -- such as high blood pressure, artery disease or diabetes -- that explained the early-age strokes.

``Even in patients with unexplained stroke,'' Levine added, ``prolapse wasn't more frequent [compared with controls].

'' People who have been diagnosed with mitral-valve prolapse, said Benjamin, should consider when the diagnosis was made. Those diagnosed before the late 1980s might not really have the condition, she noted.

``Complications are very real,'' Benjamin said, ``but the majority of patients don't have complications.''