Surgical Treatment for Mitral Regurgitation
The only proven treatment for mitral regurgitation is surgery, although medication may temporarily decrease symptoms. There are two symptoms that predicate mitral valve surgery: falling ejection fraction and dilation (increased diameter) of the left ventricle.
In patients without symptoms, whose condition has been discovered incidentally, the decision to proceed with valve surgery is based on findings that suggest that the left ventricle is beginning to decompensate under the strain imposed on it by the mitral regurgitation. These findings are typically revealed during an echocardiogram or cardiac catheterization. The two main signs of decompensation are the left ventricle no longer pumps as vigorously as it should and the left ventricle has begun to dilate.
Normally, the left ventricle ejects approximately 60 percent of the blood contained within the left ventricle with each "beat" (contraction). This percentage of blood that is ejected out of the left ventricle into the aorta with each beat is called the ejection fraction. As the heart loses the ability to contract vigorously, the ejection fraction falls. Any degree of fall below normal values is considered evidence for valve surgery. Dilation of the left ventricle beyond a certain limit also indicates the need for valve surgery.
Mitral Valve Surgery
Mitral valve surgery involves an open-heart operation. The sternum (breast bone) is split down the middle, allowing access to the heart. The heart is actually stopped during the critical parts of the operation, and a special machine is used to pump oxygenated blood throughout the body during the operation. A small part of the heart is then opened to expose the mitral valve. In some cases, surgeons replace the leaky mitral valve with an artificial valve. The most commonly used artificial valve, the St. Jude's Valve (Figure 3), is a mechanical valve made of metal and other synthetic materials. The St. Jude's valve consists of two semicircular discs that open and close with each contraction of the left ventricle. Metal valves such as these are durable, often lasting more than 20 years. The one disadvantage of mechanical valves is that there is a small potential for a blood clot to form on the valve. This blood clot can break off and travel to the brain, causing a stroke. To prevent this complication, patients who receive mechanical heart valves are treated with the blood anticoagulant warfarin (Coumadin, Jantoven, generics) to thin the blood and decrease the chance of blood clot formation.
In some cases of mitral regurgitation, the surgeon repairs the dysfunctional mitral valve instead of replacing it. It takes great skill and experience to properly repair a mitral valve, and not every dysfunctional mitral valve can be repaired. When the repair is successful, patients often do very well and do not require chronic treatment with blood thinners.
There have been significant advances in the way mitral valve surgery is performed, and in most patients, the risks for major complications are acceptably low, on the order of 3 to 5 percent in otherwise relatively healthy patients. Major complications include bleeding, infection, kidney failure, stroke, heart attack, and death.
After the surgery, the tubes that have been placed in the body to help one breathe, to monitor pressures in the heart and arteries, and to prevent blood from accumulating in the lungs are removed during the first day or two. Most patients remain in the hospital about a week after surgery and take three to four weeks to recover completely. Most patients are able to resume most leisure activities, and many return to work.
Long-Term Management After Mitral Valve Surgery
Patients who receive a mechanical heart valve must continue to take the blood thinner warfarin to decrease the chance of blood clot formation on the valve. Since a mechanical heart valve can become infected if bacteria get into the bloodstream during certain dental and medical procedures, patients who have received mechanical heart valves must be treated with endocarditis prophylaxis at the time of such procedures to decrease the chances of developing a valve infection.