In the years that followed, surgeons, engineers and other scientists began creating novel valves to replace diseased ones. On March 11, 1960, at the National Institutes of Health, Nina Starr Braunwald performed the first successful mitral valve replacement with an artificial one of her own design, a polyurethane valve with woven Teflon laces she had hand-sewn herself.
In 1976, Congress gave the Food and Drug Administration authority over medical devices, ensuring that they would be studied for safety and efficacy before reaching the market. “You’ve gone from fingers and sewing to all sorts of designs and materials,” says Michele Lyons, an NIH curator who recently assembled an exhibit on the history of heart surgery.
Today there are numerous heart valves from which to choose.
Generally, surgeons use one of two types, a synthetic, or mechanical, device or a biologic one made from cow or pig tissue chemically treated to prevent rejection. (There also are human-donor valves, but these are much less commonly used.)
There are pros and cons to each. Mechanical valves last longer than biologic ones — usually for a patient’s lifetime — and, for this reason, are recommended for patients younger than 50. But recipients almost always must take anticoagulant medication to prevent blood clots that can lodge in the valve flaps or hinges, causing potentially serious problems.
Biologic valves don’t last as long as mechanical ones — on average, about 15 years — and typically go to patients older than 70 to reduce the chances it will have to be replaced. Also, those with biologic valves need not take blood thinners. (Patients between 50 and 70 can choose either one.)
Transcatheter aortic valve replacement uses only biologic devices.
Someday patients also might be able to choose a “living” bioengineered heart valve replacement that closely resembles a native one. Scientists recently used computational modeling to design a tissue-engineered valve that, if testing proves successful, would be long-lasting, regenerative and — in the case of young people — able to grow with the patient.