If the heart valve cannot be repaired, physicians will most likely recommend heart valve replacement with either a mechanical heart valve or a tissue (biological) heart valve.
When it comes to mechanical heart valves, some surgeons still use the original cage-ball valves. These valves have a good, long-term track record. Some patients have had the cage-ball valves for more than thirty years.
The newer mechanical heart valves are made from carbon. They tend to be low profile so they take up less space and have better flow characteristics. These types of valves have been put on pulse duplicators with which accelerated wear can be tested. Tests of one hundred simulated years of use show very little actual wear on the valve. These tests indicate that, in most cases, satisfactory function can be expected for many years.
The biggest disadvantage of the mechanical heart valves is that most patients need to take an anticoagulant, also referred to as a "blood thinner," to prevent blood clots from forming on the valve itself. The most common anticoagulant is coumadin, otherwise known as warfarin. Patients who take coumadin need to get their blood tested periodically. When coumadin treatment is first started, the blood is tested every day or two, but after a few weeks, it is usually tested every couple of months to make sure the level of anticoagulation is appropriate. If the anticoagulation is too great, the patient is more prone to develop bleeding problems, which can include bleeding into the stomach, intestines, brain, or kidneys. A person with bleeding ulcers would be prone to bleed more. If you were cut, you would have a problem with abnormal bleeding. The coumadin treatment can be reversed in an emergency situation if necessary.
Another problem related to mechanical heart valves is blood clots that occur even if the anticoagulation level is appropriate. These clots can form on or near the artificial valve and travel to various parts of the body, causing strokes and other problems. Fortunately, the incidence of this is small. It is somewhat more common in patients who have mechanical artificial heart valves than in those with tissue heart valves. The biggest advantage of
the mechanical valves is that the current models tend not to wear out.
Both mechanical and tissue heart valves are more prone to become infected than your own normal heart valves. Currently, the most commonly used tissue valves come from a pig. The pig valve can be used to replace any of the four human heart valves. Another type of tissue valve is made from the pericardium of a cow. The results with this valve seem comparable to those with the pig valve.
The problem with tissue valves is that they wear out, which occurs more rapidly in children and young adults. The degeneration of these tissue valves is slower in older adults, particularly those more than seventy years of age. In patients less than seventy years old, about 15 percent to 30 percent of the tissue valves wear out within ten years. The rate of valve deterioration increases greatly after the valves have been in place for ten years.
Another type of tissue valve is the aortic homograft valve, which is used to replace the aortic valve and sometimes the pulmonary valve. These valves come from a human donor and are removed right
Above: A modern, bi-leaflet, low-profile heart valve made of carbon.
Left: A tilting disc mechanical heart valve made by Medtronic.
A pig valve without a stent (inset) can be used to correct various abnormalities of the aortic valve.
after death. Like pig valves, they tend not to last as long in younger people and last longer in patients fifty years of age or older. The incidence of blood clot problems with these tissue valves is generally quite low. Most patients with tissue valves do not need to be anticoagulated.
Some patients who undergo aortic valve replacement have a procedure called the Ross Procedure. During this operation, patients have their own pulmonary
valve removed and used to replace the aortic valve. The pulmonary valve is then replaced with a human pulmonary or aortic valve homograft. This seems to be a particularly good operation for children, in whom the valve may grow with the child. Some groups have reported excellent results with this procedure, whereas others are less enthusiastic about it. Centers that have considerable experience with the Ross Procedure tend to have the best results.
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