The mitral valve allows blood to flow from the left atrium down into the left ventricle, and it is a part of the high pressure environment of the left side of the heart. Mitral valve stenosis (or mitral valve obstruction) is a narrowing or blockage of the mitral valve. The narrowing occurs when the leaflets change shape or fuse together from an infection (rheumatic fever), a congenital heart defect, calcium deposits, or scar tissue. The narrowing decreases blood flow through the valve, allowing blood to backup in the left atrium and, eventually, the lungs. Severe mitral valve obstruction may lead to the development of pulmonary edema, pulmonary hypertension, heart failure, stroke, arrhythmias, or blood clots.
What Causes Mitral Valve Stenosis?
Mitral valve stenosis is caused by congenital defects, infection, calcium deposits, some types of medications, radiation treatment, and scar tissue formation. Before the widespread use of antibiotics to treat strep throat, rheumatic fever was the most common cause of mitral stenosis, and it still is in undeveloped countries. This infection and other infections scar the valve leaflets. The aging process can cause calcium deposits or fibrous tissue growth on the leaflets, which distorts them or causes them to fuse together. Mitral valve stenosis can accompany other congenital heart deformities in children who are born with them. No matter the cause, the stenosis process makes the leaflets appear as one single, fused leaflet.
Mitral valve stenosis usually produces no symptoms. However, atrial fibrillation, pregnancy, respiratory infections, endocarditis, and other heart conditions can trigger the development of symptoms. Symptoms can develop quickly and include:
• Shortness of breath or difficulty breathing at night
• Coughing or coughing up red-tinged sputum
• Frequent respiratory infections (e.g., bronchitis) or lung congestion
• Swelling in the feet and ankles
• A hoarse or husky-sounding voice
• Chest pain or heart palpitations
These symptoms are more likely to occur or worsen during exercise or physical exertion.
Heart valve disease is diagnosed by listening to the heart with a stethoscope; diseased heart valves make distinct clicking sounds or murmurs, and mitral valve stenosis may produce a rumbling sound that intensifies prior to contraction. Other diagnostic tests that are used to determine the underlying cause, complexity, and severity of heart valve disease include a chest x-ray, blood tests, an echocardiogram (transthoracic or transesophageal), electrocardiography (ECG) or Holter monitoring, exercise stress testing, electrophysiology (EP) studies, cardiac catheterization, and diagnostic imaging scans, such as computed tomography (CT), magnetic resonance imaging (MRI), or positron emission tomography (PET). A careful and complete diagnostic workup will help determine the timing and composition of the treatment plan.
Mitral valve stenosis can worsen with age, so patients need routine follow-up. Medications may be used to treat the symptoms, but they cannot cure the disease. Severe mitral stenosis is life-threatening, and when this occurs, the valve must be opened. This procedure, called a valvotomy, does not repair the valve; it only relieves the stenosis. It can be performed in either the cardiac catheterization laboratory or in the operating room. Mitral valve leakage is likely to develop after a valvotomy procedure, and if it does, the valve will eventually need to be replaced.
Most cardiovascular surgeons agree that mitral valve repair is the preferred method of treatment for mitral stenosis. Surgically separating or shaving back valve leaflets (a commissurotomy) can eliminate mitral stenosis and improve blood flow. If the lesion is too severe to be repaired, the mitral valve must be replaced. Replacement involves removing the defective valve and replacing it with a prosthetic valve. Prosthetic valves can be biological (made from human or animal tissue) or mechanical (made from materials such as plastic, carbon, or metal). Mechanical valves carry the risk of forming a blood clot on the new valve, so patients with mechanical heart valves must take blood-thinning medicine for the rest of their lives to prevent this complication.
Preventative Antibiotics and Heart Valve Disease
Patients with heart valve disease who have an abnormal heart or who've had heart surgery risk developing endocarditis. The American Heart Association no longer recommends taking routine antibiotics before certain dental or surgical procedures except for people at the highest risk for bad outcomes if they do develop endocarditis.
Texas Heart Institute www.texasheartinstitute.com/HIC/Topics/Cond/vmitral.cfm
Mayo Clinic www.mayoclinic.com/mitral-valve-stenosis/DS00420/DSECTION=all&METHOD=print
Medline Plus www.nlm.nih.gov/medlineplus/ency/article/00175.htm
American Heart Association www.americanheart.org/presenter.jhtml?identifier=3057276
Updated December 2009