Misdiagnosis of Heart Defect Reported
Millions of Americans have been mistakenly told by their physicians that they suffer from a defective heart valve condition that places them at higher risk of heart disease and stroke.
The defect, called mitral valve prolapse, actually affects only 2% to 3% of Americans, rather than 10% to 15% as had long been believed. Some estimates of its incidence had gone as high as 35%, and it was commonly believed to be the most common cardiac abnormality in industrialized countries.
Moreover, even for those few who actually have the condition, the risk of heart disease and stroke is no higher than for the population at large, according to two studies in today’s New England Journal of Medicine.
Many people who were mistakenly diagnosed with mitral valve prolapse were told they should receive antibiotics when having dental and other medical procedures, were forced to pay increased premiums for health insurance, and may have been prohibited from certain activities, such as flying.
“Anybody who was told 10 to 15 years ago that they had it should have the issue readdressed,” said Dr. Michelle Hamilton, co-director of the heart failure program at UCLA. And people who actually have it “should not in any way let this affect their lives or prevent them from leading a full, active life,” she added.
“This is definitely good news,” said Dr. David Faxon, chief of cardiology at the USC School of Medicine. “It puts into perspective for the first time the severity of the problem. And, in fact, it is not a very common problem.”
For a small number of patients with the most severe form of the disorder, surgery may still be needed to repair or replace the defective valve, Faxon cautioned. But, he added, the condition is curable and, after successful surgery, the patients have a much better prognosis than those who have blocked arteries or other heart problems.
The mitral valve, one of the four valves of the heart, lies between the left atrium, which receives oxygenated blood from the lungs, and the left ventricle, which pumps blood out to the body. It is composed of two flaps that open to let blood pass into the left ventricle and closes to prevent it from flowing back into the atrium.
In prolapse, one or both of the flaps do not close properly, allowing blood to leak back into the atrium. Patients with severe prolapse can develop endocarditis (a heart infection), and stress on the heart muscle associated with the problem can lead to heart failure or irregular heart rhythm.
The belief that mitral valve prolapse is common began in the early days of ultrasound (echocardiography) studies, when physicians weren’t sure what the precise shape of the flaps should be. Most researchers thought they were shaped like saucers, and any bulges were interpreted as a sign of prolapse.
Newer studies with more sophisticated ultrasound imaging techniques have shown that the flaps are actually saddle-shaped, like a Pringle’s potato chip, and that harmless bulges are quite common.
Earlier studies of the disorder had mostly been conducted on hospitalized patients, moreover, which led to overestimates of its incidence. The new study is the first to look at the general population, and is based on a long-term study of the residents of Framingham, a suburb of Boston.
Dr. Emilia J. Benjamin and her colleagues in the study, which is based at the Boston University School of Medicine, used sophisticated echocardiography and the most up-to-date criteria for diagnosing mitral valve prolapse to study 3,491 participants in the long-term project. They found that only 84 of the patients, a modest 2.4%, had mitral valve prolapse.
Among those 84 patients, furthermore, the incidence of stroke, atrial fibrillation (an irregularity in heartbeat) and heart failure was the same as in the entire population.
The studies also found that women and men are equally affected by the disorder, despite the widespread belief that it is much more common in women.
In a second study, Dr. Robert Levine of Massachusetts General Hospital (a co-author of the first study) and his colleagues examined the echocardiograms of 214 patients treated at the hospital for strokes over the last decade. All were under the age of 45, a group thought to be at increased risk of strokes triggered by mitral valve prolapse.
They found that mitral valve prolapse was present in 1.9% of the stroke patients, compared to 2.7% of a control group of 263 patients with no known heart disease. The difference was insignificant statistically.
