Artificial heart valves have been in use for more than 50 years now, so manufacturers have sorted out many of the problems and improved the technology. That said, artificial valves are still a long way from matching our own healthy natural ones, and a variety of problems can still arise.
Some artificial valves have lasted as long as 25 years without problems, and these are valves designed and inserted using the medical technology of decades ago, rather than the latest knowledge and materials, so modern valves might be expected to last even longer.
It's possible your new artificial valve could last for the rest of your life but, in some cases, valves need replacing within months, usually because they're not working properly or the heart tissue around the valve stretches, causing leakage.
There are two types of artificial heart valve:
Mechanical valves
These are made of artificial materials such as metal, plastics, silicon, Teflon and polyester. One well-known design (the Starr-Edwards valve) uses a metal ball moving within a cage to form the valve, while several others have a tilting disc design.
But both these types have design flaws that can cause problems, and the most commonly used mechanical valve is now a bileaflet design (with two semicircular leaflets that pivot on hinges). More than 170,000 bileaflet valves are implanted around the world each year.
Mechanical valves are more resistant to the constant demands placed on them (the valve must work each time the heart beats, so has to open and close at least 100,000 times a day). The latest modern materials stand up well to this wear and tear, so tend to last longer.
The downside is that, despite modern technology, the flow of blood across a mechanical artificial valve is more turbulent than normal and can lead to the formation of blood clots, which can cause a stroke.
In an effort to prevent this, the person must take anticoagulant medicines (which prevent clotting) such as warfarin for the rest of their lives. Even then, there's a small increased risk of stroke.
Bioprosthetic valves
These are made from human or animal tissue, allow a more natural flow of blood through the valve (so reducing damage to blood cells) and don’t tend to have the structural problems associated with mechanical heart valves.
Human tissue bioprosthetic valves may originate from a person who has donated organs after death, or simply from elsewhere in the body of the person who needs a new valve (known as an autograft). Mostly though, the person receives a donor or animal tissue valve.
Bioprosthetic valves made from animal sources mostly come from pig or cow tissues, but valves artificially engineered from human tissues grown in laboratories are now being developed.
With bioprosthetic valves, anticoagulant therapy is rarely needed, but they don't tend to last as long as mechanical valves, becoming torn and leaky over time. They usually have to be replaced after about ten years, or more often in children.
But they may be more suitable for women who want to have children and so want to avoid the risks linked to anticoagulants, and perhaps for older people who may be at increased risk of falls, where thinning of the blood would result in a dangerous haemorrhage.
This article was last medically reviewed by Dr Trisha Macnair in April 2008
