Learning to live with the effects of a heart attack: long-term drug therapy: anticoagulant drugs


There are various causes of valve malfunction, such as rheumatic fever, atherosclerosis in the valves, syphilis or other viral and bacterial infections or congenital defects. The two heart valves most likely to succumb to disease are the important inlet and outlet valves on either side of the left ventricle, the mitral and aortic valves. If the damage is severe and surgery is required then there are two strategies available: repair or replacement. In practice, repair is virtually never possible for the aortic valve and so a replacement is the only choice. There are more available options in the case of the mitral valve, depending on the nature of the disease and how far it has progressed. With the improvement in the types of artificial valves available, repair procedures are becoming more and more unpopular (except in mitral stenosis without calcification).

Once it is decided that a replacement valve is needed, there are two choices: either one can opt for a mechanical valve, such as the Starr, Bjork-Shilley or Saint Jude; or one can choose to use a valve made of biological materials. Whichever type of valve is inserted, the risk of mortality is low, around three to five percent, which is about the same as that for major abdominal surgery.

Mechanical valves

Mechanical valves have several advantages. They are readily available in a variety of sizes, easily sterilized, haemodynamically adequate and durable. However, people with mechanical valves have to take anticoagulants for the rest of their lives to prevent clots forming around the artificial materials, and this means a trip to hospital every six to eight weeks - a grave problem if you live in a remote area. Another drawback is that some types of mechanical valves make a clicking noise.

Biological valves

Biological valves, which have been used widely only in the last twenty years, come from a variety of sources: the aortic valves of pigs, the pericardium of calves, and valves from human donors. Using the patient's own tissue has been abandoned because, surprisingly, there was a much higher incidence of fibrosis and calcification. The biological material is treated to make it more durable and more readily accepted by the host's immune system.

Biological valves have the advantage of being silent, and patients fitted with them do not need anticoagulants. However, they are definitely less durable than their mechanical counterparts, so are not fitted in patients under the age of 40.