Harvard Heart Letter

Ask the doctor: Valve replacement: Mechanical or tissue?

Q. I'm having valve replacement surgery. I understand there are two different types of replacement valves, mechanical or tissue. What are the pros and cons of each?

A. In general, both types of valves work comparably well. Mechanical valves are made from a special type of carbon or titanium and other sturdy materials. They last longer than tissue valves but have a major drawback: blood clots can lodge in the valve flaps or hinges. These clots can prevent the valve from working properly. Or they may break off and travel through the bloodstream, causing a stroke. To avoid this problem, nearly all people who get mechanical heart valves must take anti-clotting medication (usually warfarin) for the rest of their lives. Warfarin increases the risk of bleeding, but careful monitoring limits this danger.

Tissue valves, which are made from pig heart valves or cow heart-sac tissue, only last about 15 years, but they don't usually require the use of anti-clotting drugs. As a result, they're often used in people in their late 70s and 80s, whose age makes them more vulnerable to the effects of warfarin. These people are less likely to outlive their new valves. But for older people already taking warfarin for another reason, a mechanical valve might make sense. For those younger than 65, a mechanical valve may be the best bet, since it probably won't need to be replaced. You should discuss the choice with your cardiac surgeon, as newer options are becoming available.

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