Mitral valve regurgitation (MR) is a condition in which the mitral valve, which sits between the left atrium and the left ventricle, fails to close completely when the ventricle contracts. Blood leaks backwards (regurgitates) into the left atrium instead of being pumped forward into the aorta. This reduces the effective forward output of the heart and causes the left chambers to gradually enlarge and strain.
MR can be primary (caused by disease of the valve itself) or secondary (caused by a heart condition that distorts the geometry of the left ventricle, pulling the valve leaflets apart even though the valve structure is normal). Primary causes include myxomatous degeneration (the most common cause in developed countries, causing mitral valve prolapse), infective endocarditis, and rheumatic heart disease. Secondary MR commonly occurs after a heart attack that damages the wall of the left ventricle or the papillary muscles that anchor the valve, and can also develop in dilated cardiomyopathy.
Symptoms of significant MR include breathlessness (especially on exertion), fatigue, and palpitations. Severe MR puts a volume load on the left ventricle over time, which can lead to left ventricular dilatation, reduced ejection fraction, heart failure, and atrial fibrillation.
Management depends on severity and symptoms. Mild to moderate MR with preserved left ventricular function is monitored with regular echocardiography. Severe MR causing symptoms or left ventricular impairment warrants surgical or transcatheter intervention. Mitral valve repair is preferred over replacement where anatomically feasible, as it preserves native valve function and avoids the need for long-term anticoagulation.
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