Mitral regurgitation involves blood flowing back from the left ventricle into the left atrium during systole. Often, the margins of the mitral valve cannot close during systole.
Mitral regurgitation may be caused by problems with one or more of the leaflets, the chordae tendineae, the annulus, or the papillary muscles. A mitral valve leaflet may shorten or tear. The chordae tendineae may elongate, shorten, or tear. The annulus may be stretched by heart enlargement or deformed by calcifica-tion. The papillary muscle may rupture, stretch, or be pulled out of position by changes in the ventricular wall (eg, scar from a myocardial infarction or ventricular dilation). The papillary mus-cle may be unable to contract because of ischemia. Regardless of the cause, blood regurgitates back into the atrium during systole.
With each beat of the left ventricle, some of the blood is forced back into the left atrium. Because this blood is added to the blood that is beginning to flow in from the lungs, the left atrium must stretch. It eventually hypertrophies and dilates. The backward flow of blood from the ventricle diminishes the volume of blood flowing into the atrium from the lungs. As a result, the lungs be-come congested, eventually adding extra strain on the right ven-tricle. Mitral regurgitation ultimately involves the lungs and the right ventricle.
Chronic mitral regurgitation is often asymptomatic, but acute mitral regurgitation (eg, that resulting from a myocardial infarc-tion) usually manifests as severe congestive heart failure. Dyspnea, fatigue, and weakness are the most common symptoms. Palpita-tions, shortness of breath on exertion, and cough from pulmonary congestion also occur.
A systolic murmur is heard as a high-pitched, blowing sound at the apex. The pulse may be regular and of good volume, or it may be irregular as a result of extrasystolic beats or atrial fibrillation.
Echocardiography is used to diagnose and monitor the progres-sion of mitral regurgitation.
Management of mitral regurgitation is the same as that for con-gestive heart failure. Surgical intervention consists of mitral valve replacement or valvuloplasty (ie, surgical repair of the heart valve).