Animal-Tissue Heart Valves Appear Safe

They equal mechanical devices in extending young patients' survival, study finds

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By Amanda Gardner
HealthDay Reporter

THURSDAY, Nov. 16, 2006 (HealthDay News) -- Young patients who receive replacement heart valves made from animal tissue live just as long as those who get mechanical valves, new research shows.

The results, being presented at the annual meeting of the American Heart Association, in Chicago, stand in contrast to the conventional wisdom but are in sync with current practice, experts say.

"The study confirms the value of putting in tissue valves, even in younger people," said Dr. Robert Bonow, chief of cardiology and professor of medicine at Northwestern University in Chicago, and past president of the AHA.

Heart-valve replacement is one of the oldest types of heart surgery, with two basic types of valves available: mechanical (from manmade materials) or biological (made from animal tissue).

Mechanical devices have long been considered a better option for younger people. The problem is that the risk of blood clots is higher, necessitating the use of anticoagulants (blood thinners) and frequent blood tests.

"There's a trade-off," Bonow explained. "If you put in a mechanical device, you need anticoagulants for the rest of your life, but tissue valves run the risk of degeneration and don't last as long."

Guidelines released in 1998 were "very black and white," Bonow said. "People under 65 were supposed to receive mechanical valves." But, he added, since that time, "the field has moved away from that."

Still, there's been little data to validate whether that move is the best option for younger patients, the team asserted.

"Our goal was to look at very long-term survival implications for patients receiving tissue and mechanical heart valves," said study author Dr. Vincent Chan, a cardiac surgery resident at the University of Ottawa Heart Institute in Canada.

His team analyzed 20-year follow-up data for more than 1,500 patients who had received a new aortic valve or a new mitral valve during the past 35 years. Almost 300 of the patients were under the age of 50 at the time of their first valve operation.

Among adults under age 50, 20- and 25-year survival rates did not differ significantly between individuals who had received tissue devices and those who had received mechanical devices, the researchers found.

The 20-year survival rate for aortic valve replacement was about 60 percent with mechanical valves and 72 percent with tissue valves. The 25-year survival was 47.2 percent with mechanical valves and 64.1 percent with tissue valves. After adjusting for other factors, the differences were not statistically significant, the authors stated.

People undergoing mitral valve replacement had worse survival outcomes than those undergoing aortic valve replacement, but the type of material used for the valve did not have a major impact.

Whether or not a person had coronary artery disease was the strongest predictor of survival, much stronger than what type of valve the individual received, the study found.

More information

For more on heart valves, visit the American Heart Association.

SOURCES: Vincent Chan, M.D., cardiac surgery resident, University of Ottawa Heart Institute, Ottawa, Canada; Robert Bonow, M.D., chief, cardiology, and professor, medicine, Northwestern University, Chicago, and past president, American Heart Association; Nov. 15, 2006, presentation, American Heart Association annual meeting, Chicago

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