Heart Valve Disease |
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Although valve defects may be acquired before birth, they may also be acquired later in life. The most common disease leading to such defects is rheumatic fever in childhood or youth. This is now relatively rare in developed countries but was common in the early decades of this century, and is still common in many other parts of the world, notably the Middle East and Asia. Rheumatic fever (an illness with a prolonged fever affecting the heart and joints, and often accompanied by a rash) lasts only weeks or months, but it can produce a legacy of damage to the heart valves which progresses slowly over the years. The valves most commonly affected are those on the left side of the heart—the aortic valve and, especially, the mitral valve. Usually the valves become narrowed and they may also leak and, as a result, the heart muscle has to work harder to pump blood through the narrowed opening, or to deal with an increased volume of blood caused by a leak. Not surprisingly, in the latter condition the heart tends to enlarge. As already mentioned, the heart has an amazingly large reserve; a normal heart, on exercise, can pump four to five times the flow of blood when a person is resting, and this allows an abnormal heart to cope with such an increased workload for many years. A variety of medicines are available to assist the heart with this extra load and to achieve Maximum efficiency, but there may come a time When such an obvious mechanical abnormality requires a mechanical solution: that is, surgery to repair or replace the valve. Much cardiac surgery has been undertaken in the last 20 years to repair or replace abnormal heart valves damaged by rheumatic. fever, and many patients for whom no other treatment has been available have been able to lead normal and much longer lives. As rheumatic fever has become less common, however, the need for surgery has beg to decline. Nevertheless there are other valve, which may require surgery. Processes which result in degeneration and coronary artery abnormalities both cause valves to leak. Therefore, although volume of valve surgery has lessened, there remains a considerable need which will remain in foreseeable future. Some narrowed valves, particularly the mitral the pulmonary valves, may be -restored to normal function by a simple operation which can performed without opening the heart. When the nature of the defect is less certain or when the valve has to be replaced, the heart must be opened to vi or to carry out replacement. Abnormal heart valves, unlike normal ones, are at risk of infection. This is true even when the vale abnormality is trivial. Infection caused by bacteria arrives at the valve through the bloodstream and may enter the bloodstream during surgery or dental treatment. Normally any such entry of bacteria into the bloodstream is rapidly dealt with by the body's natural defences, but infection once lodged on an abnormal valve may be very difficult to remove. For this reason it is most important that every pars known to have a valve abnormality receives antibiotics immediately before and for a few days after any procedure which might result in infection. In dentistry this rule applies even when the treatment is as minor as scaling and polishing, and also after valve surgery, as the valve, although perhaps functioning normally, is still 'abnormal'. This is a case where prevention is much better than cure; once the infection has begun, it can be extremely difficult to diagnose, and when the infection has been eradicated it is not unusual to find that the valve has been badly damaged. Finally, it must be remembered that, after valve surgery and in spite of normal heart and valve function, the valve still has to be regarded as 'abnormal'; it is necessary for those who have had such surgery to have regular check-ups at a cardiological clinic, although these can usually be infrequent. |
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