Description of Clinical Program
MITRAL VALVE REPLACEMENT
Mitral valve repair is an open heart procedure performed by cardiothoracic surgeons to treat stenosis (narrowing) or regurgitation (leakage) of the mitral valve. The mitral valve is the "inflow valve" for the left side of the heart. Blood flows from the lungs, where it picks up oxygen, and into the heart through the mitral valve. When it opens, the mitral valve allows blood to flow into the heart's main pumping chamber called the left ventricle. It then closes to keep blood from leaking back into the lungs when the ventricle contracts (squeezes) to push blood out to the body. It has two flaps, or leaflets.
The mitral valve is highlighted on this illustration of a heart. The mitral valve is the "inflow valve" for the left side of the heart. Blood flows from the lungs, where it picks up oxygen, and into the heart through the mitral valve.
Surgery may be necessary when the valve opens or closes incompletely. A stenotic (narrow) valve does not let the blood easily into the heart causing blood to "back up" and pressure to build up in the lungs. This makes it difficult for the heart to increase the amount of blood that it pumps with exercise, and may produce symptoms of shortness of breath - especially with activity. If the leaflets do not meet correctly for any reason (and many things may cause this), blood may leak backward into the lungs each time the heart pumps. Since some of the blood leaks backwards, the heart has to pump more blood with each contraction in order to push the same amount of blood forward. This is called volume overload. The heart can compensate for this overload for many months or years, provided that the leakage came on slowly and progressively. Eventually, the heart begins to fail and patients show symptoms of shortness of breath or fatigue (tiredness).
When it opens (left), the mitral valve allows blood to flow into the heart's main pumping chamber called the left ventricle. It then closes (right) to keep blood from leaking back into the lungs when the ventricle contracts (squeezes) to push blood out to the body. It has two flaps, or leaflets.
WHAT CAUSES MITRAL VALVE PROBLEMS?
Mitral valve problems are rarely caused by a birth defect, otherwise known as a congenital condition. More often, simple "wear and tear" may cause part of the valve mechanism to fail. This is called "degenerative disease". This may be related to advancing age, although many young people will have this condition as well. Rheumatic fever may damage the mitral valve causing stenosis or regurgitation. Occasionally the mitral valve is damaged by infection or bacterial endocarditis. Ischemic heart disease (coronary artery disease) can also cause the mitral valve to leak.
WHAT ARE THE SURGICAL OPTIONS?
Many mitral valves can be repaired, especially if they leak due to degenerative disease. A separate discussion of mitral valve repair will be available through this site. In many cases, however, the valve is too damaged to permit repair and the valve must be replaced with a prosthetic (artificial) valve. Valves damaged by rheumatic disease often must be replaced.
In general terms, there are two types of artificial valves available - mechanical valves made entirely from metal and pyrolytic carbon - or biological valves - made from animal tissues. Each has advantages and disadvantages with respect to durability (how long they will last) and risk of blood clots forming on the valve. The choice of which type to use should be made by you and your doctors taking the following into consideration:
- Your age
- Other medical conditions
- Your preferences with regard to medications and the risk of reoperation
- Your lifestyle.
Examples of the valves that your cardiothoracic surgeon might use are pictured below.
A Mechanical Valve (left) and a Biological Valve (right)
There are a number of excellent mechanical prostheses available today. All perform equally well. The principle advantage of mechanical valves is their excellent durability. The valves available today simply do not wear out! Their main disadvantage is that blood has a tendency to clot on all mechanical valves. If this happens the valve will not function normally. Therefore, patients with these valves must take anticoagulants (blood thinners) for life. There is also a small but definite risk of blood clots causing stroke, even when taking anticoagulants.
There are a variety of biological alternatives for mitral valve replacement. Most are made from pig aortic valves. Their key advantage is that they have a reduced risk of blood clots forming on the valve itself causing valve dysfunction or stroke. The key disadvantage of biological or tissue valves is that they have more limited durability as compared with mechanical valves. They will wear out given enough time. The rate at which they wear out, however, depends on the patient's age. A young boy might wear out such a valve in only a few years, while the same valve might last 10 years in a middle aged person, and even longer in a patient over the age of 70. Of course, as we grow older we expect that we will not need the valve for as many years as our life expectancy is less. The general consensus is that a tissue valve will not need to be replaced if used in a patient over the age of 70 years.
WHAT ARE THE RISKS OF SURGERY?
Your cardiologist and cardiothoracic surgeon can best determine your individual risk of surgery. It will depend on your age, general condition, specific medical conditions, and your heart function.
WHAT WILL MY CONDITION BE LIKE AFTER MITRAL VALVE REPLACEMENT?
After successful mitral valve replacement you can expect to return to your preoperative condition or better, although this may take time. Anticoagulation (blood thinners) with Coumadin is often prescribed for 6 weeks to 3 months postoperatively for those with biological valves, and for life for those with mechanical valves. Once your wounds have healed there should be few, if any, restrictions on your activity. (For more information about your recovery, refer to What to Expect After Your Heart Surgery.)
You will require prophylactic antibiotics as a preventive measure against infection whenever you have dental work done. Always tell your doctor or dentist that you have had valve surgery before any surgical procedure.