MITRAL VALVE REPAIR

Mitral valve repair
Definition : Mitral valve repair is a surgical procedure used to improve the function of a stenotic (narrowed), prolapsed, or insufficient mitral valve of the heart.

Purpose
The mitral valve can become diseased, preventing it from adequately controlling the direction of the blood flow between the left atrium and left ventricle. It also can become insufficient (regurgitant), letting blood flow backwards into the left atrium (upper chamber) from the left ventricle (lower chamber) during ventricular contraction (systole). The mitral valve also can become stenotic (narrowed), preventing the flow of blood from the left atrium into the left ventricle during ventricular filling (diastole). In mitral valve prolapse, one or more of the mitral valve’s cusps protrude back into the left atrium during ventricular contraction. Mitral valve repair is performed to improve the function of the diseased valve so that it correctly controls the direction of blood flow.

Demographics
Approximately 65,000 valve repairs and replacements are performed in the United States annually. Twice as many women as men are affected by mitral valve stenosis. About 60% of patients with mitral valve stenosis have had rheumatic fever. After rheumatic fever there is usually a latency period of 10–20 years before symptoms of mitral valve stenosis appear. The prevalence of mitral valve stenosis has declined in the United States because there has been a decline in the number of cases of rheumatic fever. Mitral valve stenosis may be present at birth (congenital); however, it rarely occurs alone but rather in conjunction with other heart defects.

Mitral valve prolapse is the most common condition of the heart valves, and is present in about 2% of the general population. Recent studies indicate that similar numbers of men and women have mitral valve prolapse. Having this condition does not guarantee that mitral insufficiency will develop. Patients with a history of rheumatic fever, coronary artery disease, infective endocarditis, or collagen vascular disease also may develop mitral insufficiency.

Description
Cardiac monitoring is instituted and general anesthesia is provided. The surgeon uses a sternotomy to access the heart and great blood vessels. Anticoagulation is given as cannulae are inserted into the great vessels, femoral vessels, or a combination. Cardiopulmonary bypass is instituted. The heart is arrested as the cross clamp is applied to the ascending aorta to stop blood flow through the organ. The surgeon opens the heart to visualize the mitral valve. He/she may expose the mitral valve by opening the right atrium and then opening the atrial septum. Another approach requires a large left atrium that can be opened directly, making the mitral valve visible.

Mitral commissurotomy
Mitral commissurotomy is used to repair mitral stenosis associated with rheumatic disease. The commissures - openings between the valve leaflets - are manually separated by the surgeon. Fused chordae tendineae (cords of connective tissue that connect the mitral valve to the papillary muscle of the heart’s left ventricle) are separated, along with papillary muscles. Calcium deposits may be removed from the valve leaflets. The left atrial appendage is removed to reduce the risk of future thromboemboli (blood clot) generation.

Chordae tendineae repair
The chordae tendineae can become lengthened or rupture, resulting in mitral valve prolapse. A skilled surgeon repairs the mitral valve structure by placing sutures in the valve leaflets to stabilize the valve structure. Typically the posterior leaflet requires this type of repair.

Annuloplasty
A flexible fabric ring is sutured to the valve annulus to provide support and reconstruction for the patient’s valve annulus. The size of the ring is selected to match the patient’s own valve size. This repair allows the valve to function normally.

The heart is closed with sutures. Deairing of the heart is performed prior to removal of the cross clamp. When the cross clamp is removed, deairing continues to ensure that no air is delivered to the systemic circulation. At this time a transesophageal echocardiogram (TEE) may be used to test that the valve is functioning correctly and that the heart is free of air. If the surgeon is not satisfied with the repair, mitral valve replacement is performed. Once the surgeon is satisfied that the valve is working correctly, cardiopulmonary bypass is terminated, anticoagulation is reversed, and the cannulae are removed from the vessels. The sternotomy is closed. Permanent stainless steel wires are used to hold the sternum bone together. The skin incision is closed with sutures, and sterile bandages are applied to the wound.