Acute Mitral Regurgitation :  This may be caused by chordal rupture, infective endocarditis or acute myocardial infarction. In acute myocardial infarction, one of the papillary muscles may rupture leading to acute severe mitral regurgitation. Infarction involving the base of the papillary muscle along with contiguous myocardium may lead to papillary muscle dysfunction resulting in mitral regurgitation.

There is usually sudden and severe onset of pulmonary venous hypertension and pulmonary oedema. There is no significant enlargement of left atrium and left ventricle. The murmur is not pan systolic and may have a crescendo-decrescendo character ending well before S2. X-ray will show a pattern of pulmonary oedema and ECG is diagnostic of infarction. Echocardiogram is diagnostic.