Causes
Mitral regurgitation results from any process that disrupts the valve leaflets, chordae, papillary muscles, or annulus. Common chronic causes include mitral valve prolapse (myxomatous degeneration), rheumatic heart disease, and functional MR from left ventricular dilation. Acute mitral regurgitation is often caused by papillary muscle rupture after myocardial infarction or by infective endocarditis damaging the valve.
The Murmur and Presentation
The classic finding is a holosystolic (pansystolic) murmur heard best at the cardiac apex and radiating to the left axilla, often with a soft S1. Chronic MR develops gradually as the left atrium and ventricle enlarge to accommodate the regurgitant volume, and patients may be asymptomatic for years before developing dyspnea, fatigue, and atrial fibrillation. Acute MR, by contrast, presents dramatically with sudden severe pulmonary edema and hemodynamic instability.
Diagnosis
Echocardiography is the key test, confirming regurgitation, identifying the mechanism, quantifying severity, and assessing left atrial and ventricular size and function. The ECG and chest radiograph may show chamber enlargement. Because chronic MR can silently damage the ventricle before symptoms appear, serial echocardiography is used to monitor and time intervention.
Treatment
Acute severe mitral regurgitation is an emergency requiring stabilization (afterload reduction, sometimes an intra-aortic balloon pump) and urgent surgery. Chronic severe MR is treated with mitral valve repair (preferred when feasible) or replacement, timed to symptoms or evidence of ventricular dysfunction or enlargement. Guideline heart-failure therapy is used for functional MR, and transcatheter repair is an option for selected high-risk patients.