All artificial heart valves used for replacement have disadvantages. If a tissue valve is used (usually made from cow or pig tissue) it will wear out over time. This may not be important for an older person who will die before the valve wears out, but it is a problem for a younger person because they will have to have another heart operation to replace the worn out tissue valve, usually in about ten years.
A mechanical heart valve will last indefinitely, meaning that no further surgery will be required. There are two major problems with mechanical valves.
Mechanical heart valves cause blood clots that can break off and go to the brain (causing a stroke) or to other organs or limbs. In some cases, the blood can clot on the valve itself, causing it to malfunction. Blood thinners such as warfarin must be taken to prevent the blood clots from forming. This causes quite a change in lifestyle. The patient must have blood tested regularly to make sure the blood is not too thick or too thin, and the medicine must be taken every day and in just the right dose.
People on warfarin can develop bleeding problems, and as patients get older, this becomes a significant risk, such as if they fall or have an ulcer. If some other surgery or procedure is required, the warfarin must be stopped to prevent bleeding during the operation, and this puts the patient at risk. The risk of a blood clot problem with a mechanical valve is 1-2% per year, and the risk of a bleeding problem is 1-2% per year. For a younger person who is 40 who lives to be 80, that means there is a 40-80% chance of a bleeding problem and a 40-80% chance of a blood clot problem over their lifetime. People who have physically demanding jobs with an increased risk of injury, such as construction workers, may be at increased risk for bleeding while on warfarin.
Finally, warfarin causes birth defects when it is taken during pregnancy, so this is a problem for young women who wish to have children.