Mitral Valve Repair
Mitral Valve Repair
Mitral valve repair is a surgical procedure used to improve the function of a stenotic (narrowed), prolapsed (slipped from its normal position), or insufficient (weakened) mitral valve of the heart.
The mitral valve controls the blood flow between the left atrium (upper chamber) and left ventricle (lower chamber) of the heart. When the mitral valve functions correctly, blood flows in one direction only— from the atrium to the ventricle. Then the valve becomes diseased or weakened, blood can backflow from the ventricle to the atrium when the ventricle contracts (systole). The mitral valve also can become 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 amount and direction of blood flow.
Mitral valve prolapse is the most common heart valve defect. In the United States it is present in about 2–6% of the population. The defect is believed to have an inherited component and is seen twice as often in women as in men. Having this condition does not automatically mean 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.
Mitral valve stenosis almost always is the result of having rheumatic fever in childhood. Rheumatic fever occurs in some people after a group A streptococcal throat infection (commonly called strep throat). Genetics appears to play a role in determining who develops rheumatic fever after a strep infection, with women more likely than men to progress to the disease. After rheumatic fever subsides, 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. In the United States in 2005, about one case of rheumatic fever occurred for every 100,000 people. Rheumatic fever is much more common in developing countries (100-150 cases per 100,000 in India, for example), and thus the rate of mitral valve stenosis is also higher. Mitral valve stenosis may be present at birth (congenital); however, it rarely occurs alone but rather in conjunction with other heart defects.
Mitral valve repair is done under general anesthesia with continuous cardiac monitoring. Uncomplicated mitral valve surgery normally takes 2–3 hours. In traditional mitral repair, the surgeon uses a sternotomy to access the heart and large blood vessels. Anticoagulation drugs are given as cannulae are inserted into the large veins. Cardiopulmonary bypass (use of a heart-lung machine) is instituted. The heartbeat is stopped as blood vessels are clamped to prevent blood flow through the heart. The surgeon opens the heart to see the mitral valve. He/she may expose the mitral valve by opening the right atrium and then opening the atrial septum (tissue dividing the atria). Another approach requires a large left atrium that can be opened directly, making the mitral valve visible.
Mitral commissurotomy is used to repair mitral stenosis associated with rheumatic fever. 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 (the valve slipping out of place). 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.
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. De-airing of the heart is performed before removal of the clamps. When the clamps are removed, de-airing continues to
Acute— Rapid onset.
Annulus— A ring-shaped structure.
Anticoagulants— Drugs that are given to slow blood clot formation.
Atrium (plural Atria)— The right or left upper chamber of the heart.
Cannula (plural cannulae)— A small, flexible tube.
Cardiac catheterization— A diagnostic procedure (using a catheter inserted through a vein and threaded through the circulatory system to the heart) which does a comprehensive examination of how the heart and its blood vessels function.
Chordae tendineae— The strands of connective tissue that connect the mitral valve to the papillary muscle of the heart’s left ventricle.
Commissures— The normal separations between the valve leaflets.
Doppler echocardiography— A testing technique that uses Doppler ultrasound technology to evaluate the pattern and direction of blood flow in the heart.
Endocarditis— Infection of the heart endocardium tissue, the inner most tissue and structures of the heart.
NYHA heart failure classification— A classification system for heart failure developed by the New York Heart Association. It includes the following four categories: I, symptoms with more than ordinary activity; II, symptoms with ordinary activity; III, symptoms with minimal activity; IV, symptoms at rest.
Rheumatic carditis— Inflammation of the heart muscle associated with acute rheumatic fever.
Rheumatic fever— An inflammatory disease that arises as a complication of untreated or inadequately treated strep throat infection. Rheumatic fever can seriously damage the heart valves.
Sternotomy— A surgical opening into the thoracic cavity through the sternum (breastbone).
Systemic circulation— Circulation supplied by the aorta including all tissue and organ beds, except the alveolar sacs of the lungs used for gas exchange and respiration.
Thromboemboli— Blood clots that develop in the circulation and lodge in capillary beds of tissues and organs.
Transesophageal echocardiography— A diagnostic test using an ultrasound device that is passed into the esophagus of the patient to create a clear image of the heart muscle and other parts of the heart.
ensure that no air enters 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 blood 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.
Minimally invasive mitral valve repair
In the mid-2000s, some cardiac surgery centers began performing robot-assisted minimally invasive mitral valve repair. In minimally invasive repair, a 2–3 inch (5–8 cm) opening is made in the side of the chest instead of reaching the heart by breaking the sternum. Then, with the assistance of a robotic arm, the valve is repaired. Minimally invasive mitral valve repair may not be appropriate for all patients, but when it is, it offers the advantages of less chance of infection and blood loss, a shorter hospital stay, and a faster, less painful recovery.
Mitral valve stenosis is diagnosed by history, physical examination, listening to the sounds of the heart (cardiac auscultation), chest x ray, and ECG. Patients may have no symptoms of a valve disorder or may have shortness of breath (dyspnea), fatigue, or pulmonary edema (fluid in the lungs). Other patients present with atrial fibrillation (a cardiac arrhythmia) or an embolic event (result of a blood clot, i.e., heart attack or stroke). Doppler echocardiography is the preferred diagnostic tool for evaluation of mitral valve stenosis, and can be performed in conjunction with non-invasive exercise testing by treadmill or bicycle. Cardiac catheterization is reserved for patients who demonstrate discrepancies in Doppler testing. Both left- and right-heart catheterization should be performed in the presence of elevated pulmonary artery pressures.
A diagnosis of mitral insufficiency requires a detailed patient history. Listening to the heart (auscultation) reveals the presence of a third heart sound. Chest x ray and ECG provide additional information. Again, Doppler echocardiography provides valuable information. Exercise testing with Doppler echocardiography can show the true severity of the disease.
After initial findings, patients may be followed with repeat visits and testing to monitor disease progress. If the patient has reached NYHA Class III or IV, replacement is considered. Severe pulmonary hypertension with pulmonary artery systolic pressures greater than 60 mm Hg is considered an indication for surgery. Left ventricular ejection fraction less than 60% also is an indication for surgery.
The patient receives continued cardiac monitoring in the intensive care unit and usually remains in intensive care for 24-48 hours after surgery. Ventilation support is discontinued when the patient is able to breathe on his/her own. If mechanical circulatory support and inotropic drugs (substances that stimulate heart muscle contractions, e.g. digitalis) were needed during the surgical procedure, they are discontinued as cardiac function recovers. Tubes draining blood from the chest cavity are removed as bleeding from the surgical procedure decreases. Prophylactic antibiotics are given to prevent infective endocarditis and prevent the recurrence of rheumatic carditis.
If the patient recovers normally, discharge from the hospital occurs within a week of surgery. At discharge, the patient is given specific instructions about wound care and infection recognition, as well as contact information for the physician and guidelines about when a visit to the emergency room is indicated. Within three to four weeks after discharge, the patient is seen for a follow-up office visit with the physician, at which time physical status will have improved for evaluation. Thereafter, asymptomatic, uncomplicated patients are seen at yearly intervals. Few limitations are placed on patient activity once recovery is complete.
There are always risks associated with general anesthesia and cardiopulmonary bypass. Risks specifically associated with mitral valve repair include embolism, bleeding, or operative valvular endocarditis. When valve repair does not produce adequate results, then increased operative time is required to replace the mitral valve. If the patient’s mitral valve is replaced with a mechanical valve, the patient must take an anticoagulation drug, such as Coumadin, for the rest of his/her life. An inadequately repaired valve, if left untreated, results in continued myocardial dysfunction resulting in pulmonary edema, congestive heart failure, and systemic thromboemboli generation.
WHO PERFORMS THE PROCEDURE AND WHERE IS IT PERFORMED?
Cardiothoracic and cardiovascular surgeons perform mitral valve repair. Surgeons are trained during their residency to perform these procedures, although a certain level of skill is required for perfection of the technique. Medical centers that perform cardiac surgery are able to provide mitral valve repair.
Patients treated by mitral valve repair for mitral insufficiency can expect improved myocardial function and relief of symptoms. Oxygen consumption by skeletal muscle continues to improve. Cardiac output improves and pulmonary hypertension resolves over several months after the initial decrease in left atrial pressure, pulmonary artery pressure, and pulmonary arteriolar resistance.
Excellent results in terms of improved cardiac function and symptom relief also are expected for patients that undergo mitral valve repair for mitral stenosis.
Operative mortality associated with mitral valve repair for stenosis is 1-3%. The prognosis for restenosis (re-narrowing) is 30% at five years and 60% at nine years; additional surgery is required in 4-7% of patients at five years. Eighty to 90% of patients whose mitral valve stenosis was repaired by commissurotomy are complication free at five years after surgery.
Mitral valve repair for mitral insufficiency is the preferred approach because it preserves the valvular apparatus and left ventricular function. It also eliminates the risk of mechanical valve failure and the need for lifelong anticoagulation.
QUESTIONS TO ASK THE DOCTOR
- Is mitral valve repair the best treatment choice for my condition?
- Am I a candidate for minimally invasive mitral valve repair?
- How many of these procedures has the surgeon performed in the last year? in the last five years?
- What is the surgeon’s morbidity and mortality rate with mitral valve repair?
- What will happen if the repair fails?
- What type of follow-up care is required during the first year after surgery and throughout the rest of my life?
- What type of complications can be encountered both acute and chronic?
The asymptomatic patient with a history of rheumatic fever can be treated with prophylactic antibiotics and followed until symptoms are appear. If atrial fibrillation develops antiarrhythmic medications can be used for treatment. Atrial defibrillation may relieve atrial fibrillation. Anticoagulants may be prescribed to prevent the occurrence of systemic embolization.
Mitral valve repair for mitral regurgitation is not as successful if the anterior leaflet is involved. Rheumatic, ischemic, or calcific diseases decrease the likelihood of repair in even the most skilled hands. In the absence of mitral valve replacement, mitral valve repair is indicated.
ICON Health Publications. The Official Patient’s Sourcebook on Mitral-Valve Prolapse. San Diego, CA: ICON Health Publications, 2006.
Bonow, R., et al. “ACC/AHA 2006 Guidelines for the Management of Patients with Valvular Heart Disease.” Circulation. 114 (2006) e84-e231. http://circ.ahajournals.org/cgi/reprint/114/5/e84.
American Heart Association. 7272 Greenville Avenue, Dallas, TX 75231. (800) 242-8721. http://www.americanheart.org.
Gillinov, A, Marc. “Mitral Valve Repair.” Cleveland Clinic Heart and Vascular Institute.http://www.clevelandclinic.org/heartcenter/ [accessed May 16, 2008].
“Mitral Valve Repair Using Robotic Surgery.” St. Joseph’ Hospital (Atlanta) Center for Robotic Surgery. [cited February 5, 2008]. http://www.stjosephsatlanta.org/center-for-robotic-surgery/heart/mitral-valve-repair-robotic-surgery.html.
Allison Joan Spiwak, MSBME
Tish Davidson, A. M.