As a result of the findings, the researchers suggest that patients with severe regurgitation promptly undergo cardiac surgery. Enriquez-Sarano estimates that 900,000 to 1 million people fall into this category. Of the 232 patients who underwent surgery in the study, 209 had their mitral valves repaired using their own tissue, and 21 had their valves replaced with mechanical valves or animal tissue. Two patients with more complicated cases required coronary bypass surgery. Corrective surgery for defective valves considerably reduced the rates of death from cardiac causes and decreased risks of heart failure compared with those who did not get surgery, according to the study. Patients with severe regurgitation were most likely to undergo surgery.
A diagnosis of mitral valve regurgitation often comes as a surprise during a routine physical. That's when the physician notices a heart murmur -- an "extra sound" when listening to the patient's heart, said Farzad Najam, clinical assistant professor of surgery at George Washington University (GWU) Medical Center and visiting cardiac surgeon at GWU Hospital. A definitive diagnosis typically comes from an echocardiogram, which provides images of the heart's structure and blood flow. The images show the extent of regurgitation, helping doctors decide when surgery is needed.
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But sometimes diagnosis of severe regurgitation comes after the condition has done damage. "A lot of people go without evaluation until they become symptomatic. That's when a cardiologist evaluates them," Najam said.
A common cause of regurgitation is mitral valve prolapse, a condition in which the mitral valve billows out, preventing it from closing properly. About 15 to 20 percent of people with mitral valve prolapse develop mitral valve regurgitation, Najam said. Other causes of regurgitation include congenital defects, rheumatic heart disease, atherosclerosis (hardening and thickening of the arteries), hypertension, left ventricular enlargement, endocarditis (heart valve infection), untreated syphilis and cardiac tumors.
Risk factors for the condition include a family or individual history of certain diseases and use of the diet drugs fenfluramine and dexfenfluramine, both now withdrawn from the market.
Although most surgery patients in the Mayo Clinic study had their valves repaired rather than replaced, this proportion is not typical. Only about a third of the nearly 22,000 mitral valve procedures performed in the United States in 1999 and 2000 were repairs; the rest involved replacements using mechanical valves or animal tissue, according to findings published in the Annals of Thoracic Surgery in 2003.
Advantages of repair surgery include increased durability, lower risk of infection and less dependence on post-surgery medication. Replacement with mechanical valves require patients to take blood thinners for the rest of their lives. But repairs are more time-consuming than replacements and require a complex technique that is "difficult to learn without specialized training and difficult to incorporate into a surgical practice" if the facility doesn't do many such procedures, according the 2003 study.
Minimally invasive surgery for mitral valve repair, performed at some surgical centers, promises a shorter recovery and a smaller -- no more than two-inch -- incision. Standard repair surgery typically requires a large incision across the breastbone.
"Generally people seem to get back to work in about half the time [after minimally invasive repair surgery] -- two to three weeks as opposed to a month or a month and a half," said Gammie of the University of Maryland Medical Center, which performs about 150 mitral valve operations a year -- 85 percent of which are repairs. "And it's much better to fix the valve than to replace it."
The new study calls for a clinical trial in the future to confirm the results. Some doctors said they hope these early findings will encourage family physicians to refer patients with heart murmurs to cardiologists sooner to confirm or rule out mitral valve regurgitation.