Echocardiography (severity, mechanism, EF, LA size).
First-line Treatment
Surgical or transcatheter repair/replacement for severe/symptomatic disease. Acute severe = surgical emergency; afterload reduction (nitroprusside) as a bridge.
High-Yield Pearl
Acute MR from post-MI papillary muscle rupture is a can't-miss cause of a new murmur + cardiogenic shock.