Text A. Mitral Valve Regurgitation

 

Mitral valve regurgitation (mitral incompetence, mitral insufficiency) is leakage back through the mitral valve each time the left ventricle contracts.

As the left ventricle pumps blood out of the heart and into the aorta, some blood leaks back into the left atrium, increasing the volume and pressure there. This, in turn, increases blood pressure in the vessels leading from the lungs to the heart, resulting in fluid buildup (congestion) in the lungs.

Rheumatic fever used to be the most common cause of mitral valve regurgitation. But today, rheumatic fever is rare in countries that have good preventive medicine. In North America and Western Europe, for instance, the use of antibi­otics for strep throat (streptococcal infection of the throat) now largely prevents rheumatic fever. In these regions, rheumatic fever is a common cause of mitral valve regurgitation only among elderly people who didn't have the benefit of an­tibiotics in their youth. In countries that have poor preventive medicine, however, rheumatic fever is still common, and it's a common cause of mitral valve regurgitation.

A more common cause of mitral valve regurgitation is a heart attack, which can damage the supporting structures of the mitral valve. Another common cause is myxomatous degeneration, a condition in which the valve gradually becomes floppy.

Symptoms

Mild mitral valve regurgitation may not pro­duce any symptoms. The problem may be recog­nized only if a doctor, listening through a stetho­scope, hears a distinctive heart murmur caused by blood leaking back into the left atrium when the left ventricle contracts.

Because the left ventricle has to pump more blood to make up for the blood leaking back to the left atrium, it gradually enlarges to increase the force of each heartbeat. The enlarged ventri­cle may cause palpitations (an awareness of forceful heartbeats), particularly when a person lies on the left side.

The left atrium also tends to enlarge to accom­modate the extra blood leaking back from the ven­tricle. A very enlarged atrium often beats rapidly in an irregular disorganized pattern (atrial fibrillation), which reduces the heart's pumping efficiency. A fibrillating atrium is really just quiv­ering, not pumping, and the lack of proper blood flow through it allows blood clots to form. If a clot becomes detached, it's pumped out of the heart and may block a smaller artery, possibly causing a stroke or other damage.

Severe regurgitation reduces the forward flow of blood enough to cause heart failure, which may produce coughing, shortness of breath on exer­tion, and swollen legs.

Diagnosis

Doctors can usually recognize mitral valve regurgitation by its characteristic murmur—a sound heard through a stethoscope when the left ventricle contracts. An electrocardiogram (ECG) and chest x-rays indicate that the left ventricle is enlarged. The most informative test is echocardiography, an imaging technique that uses ultra­sound waves. This test can produce an image of the faulty valve and indicate the severity of the problem.

Treatment

If regurgitation is severe, the valve needs to be repaired or replaced before the left ventricle be­comes so abnormal that the problem can't be cor­rected. Surgery may be performed to repair the valve (valvuloplasty) or to replace it with a me­chanical one or one made partly from a pig's valve. Repairing the valve eliminates the regurgi­tation or reduces it enough to make the symp­toms tolerable and prevent damage to the heart. Each type of replacement valve has advantages and disadvantages. Although mechanical valves are usually effective, they increase the risk of blood clots, so anticoagulants usually are taken indefinitely to reduce this risk. Pig valves work well and don't pose a risk of blood clots, but they don't last as long as mechanical valves. If a re­placement valve fails, it must be replaced imme­diately.

Atrial fibrillation also may require treatment. Drugs such as beta-blockers, digoxin, and verapamil can slow the heart rate and help control the fibrillation.

The surfaces of damaged heart valves are sus­ceptible to serious infection (infective endocar­ditis). Anyone with a damaged or artificial valve should take antibiotics before a dental or surgical procedure to prevent infection.

Notes:

interfere вмешиваться, мешать

distinctive отличительный, характерный, особенный

accommodate вмещать, аккомодировать

detached отделившийся

swollen вздутый, отёкший

faulty неисправный

susceptible восприимчивый