The first mechanical valve (in 1961) was the “ball in cage” design and is still in use today. A number of other designs have been tried as well, primarily those with a single or two tilting disks. The mechanical valve is a sturdy device that can be manufactured to meet demand. Implantation of the mechanical valve is straightforward and relatively simple.
The Achilles Heel of the mechanical valve is the problem of clot formation and the side effects of clot preventing blood thinners. Clots on valves rarely cause the valve to “stick” open or partially closed; more commonly, little bits of clot form and flick off the valve to travel down the bloodstream to remote locations. This can cause blockage of arterial branches anywhere in the body, such as in the eyes, fingers, kidneys, intestine, spleen, legs, or the brain where it can cause a stroke.
Warfarin (Coumadin) is administered to prevent clots from forming on the mechanical valves. Coumadin is the primary medication used to slow down the body’s clotting system. However, too much of this medicine can lead to serious bleeding complications from ulcers, injuries, or even spontaneous bleeding in the brain, kidneys or other internal structures.
Patients taking Coumadin must be monitored periodically with blood tests to assure the dosage is right. Contact sports or activities, such as skiing, that risk blunt trauma can be dangerous. Bleeding can complicate surgical procedures for other conditions, or the temporary interruption of the blood thinner can lead to clot formation. Some foods (notably broccoli) and many medicines (especially aspirin and antibiotics) change the effect of Coumadin. These drug and food interactions must be avoided or monitored closely.
Further, the rigid nature of the mechanical valve makes it slightly more difficult to implant in a calcified or rigidly scarred orifice. Regurgitation flowing between the valve housing and the native wall between stitches (paravalvular leaks) are more common than with the more flexible tissue valves. This ongoing trauma to the blood cells may produce hemolysis (breakage of the red blood cells) leading to anemia.
A minor problem, but occasionally annoying, is the fact that many patients can hear the valve clicking with each heartbeat. This is not insurmountable, but it makes playing cards a bit dicey at times!
All this notwithstanding, a mechanical valve may still be the best choice for some patients and has served many very well for a long time. One must recognize the need for vigilance in monitoring the INR and taking Coumadin faithfully as well as understanding the limitations on lifestyle that may be required.