Introduction to Mitral Valve Surgery

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. (Click on the illustration to enlarge it.)

Occasionally, the mitral valve is abnormal from birth (congenital). More often the mitral valve becomes abnormal with age (degenerative) or as a result of rheumatic fever. In rare instances the mitral valve can be destroyed by infection or a bacterial endocarditis. Mitral regurgitation may also occur as a result of ischemic heart disease (coronary artery disease).

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. (Click on the illustration to enlarge it.)

Often the mitral valve is so damaged that it must be replaced (refer to Mitral Valve Replacement). Occasionally, however, the valve can be repaired rather than replaced. One type of repair is a procedure called mitral commisurotomy. Mitral commisurotomy can be performed for some valves that are narrow or "stenotic" either from birth or from damage by rheumatic fever. Most often today, rheumatic mitral stenosis is treated by balloon valvuloplasty, a procedure performed in the cardiac catheterization laboratory by interventional cardiologists. Using a catheter with a balloon on the end, the balloon is expanded inside the valve "stretching" it open.

More often mitral valve repair is performed to correct a leaking or regurgitant valve. Congenital mitral regurgitation may be due to a cleft mitral valve (a valve with a separation or cleft down the middle) associated with an atrial septal defect, a type of hole in the heart between the low pressure chambers or atria. Such valves can sometimes be repaired simply by closing the cleft with sutures. Valves regurgitant due to bacterial endocarditis can occasionally be repaired; however the majority of mitral valve repairs are performed for degenerative disease. Degenerative mitral valve disease may be due to an elongation or rupture of the chordal apparatus, the "heart-strings" that support the valve normally, or due to a more generalized weakness of the valve itself such as the "floppy valve" syndrome in which all of the components of the valve are enlarged and elongated.

Not all mitral valves can be repaired. A preoperative echocardiogram may help your surgeon predict the likelihood of repair, but cannot guarantee it. Mitral valves that are regurgitant due to rheumatic fever are often both stenotic and regurgitant, and are often beyond repair.

Why Is Surgery Necessary?

The mitral valve is the inflow valve into the left side of the heart. It closes during systole (when the ventricle contracts or squeezes blood out into the aorta and the rest of the body). When the mitral valve leaks, blood flows backwards into the lungs. The ventricle must therefore pump more blood with each contraction to produce the same forward output of blood throughout the body. This resulting condition is called a volume overload. The heart can compensate for this volume overload for many months or years (provided the leakage came on slowly and progressively), but it eventually begins to fail producing symptoms of shortness of breath or fatigue.

When Is Surgery Necessary?

The indications for mitral valve repair are undergoing constant re-evaluation. Recent evidence suggests that earlier surgical intervention, particularly if repair is possible, may prevent irreversible damage to the heart. The decision regarding when to proceed with surgery should be made with your doctor. This decision will require judgment regarding the risk of surgery and the benefits available from surgery. In some cases blood pressure medications, such as ACE-inhibitors can significantly relieve symptoms.

Severe mitral regurgitation in the presence of symptoms of congestive heart failure is usually an indication for surgery. Severe regurgitation diagnosed by echocardiography, even without symptoms, may be sufficient to warrant repair. Enlargement of the left atrium, particularly in the setting of the recent onset of an irregular heartbeat (atrial fibrillation, premature atrial contractions, paroxysmal atrial tachycardia, etc.) is considered by many doctors also to be an indication for surgery.

What are the Results of Mitral Valve Repair?

The first thing to remember is that a surgeon can predict the likelihood of repair before surgery, but cannot guarantee it. If repair is possible, the likelihood of long-term success is good, particularly for degenerative valve disease. Depending upon the underlying abnormality there may be an 85 to 95% chance of needing nothing further done to the valve over the next 10 years. If a more complex repair was required for degenerative disease, the chances of long-term freedom from reintervention (further surgery) may be less. If a valve was damaged by rheumatic fever, the disease may progress even after the repair, making the chances of the repair holding up in the long run less. Some surgeons are, therefore, reluctant to repair rheumatic valves. The results of repair of mitral regurgitation associated with coronary artery disease are the most difficult of all to predict.
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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. Anticoagulation (blood thinners) with Coumadin is often prescribed for 6 weeks to 3 months postoperatively. Generally this prescription is not required in the long term unless other indications for anticoagulation such as atrial fibrillation are present. Once wounds have healed there should be few if any restrictions on a patient's activity.

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. (Source: Society of Thoracic Surgery.