Early systolic murmurs begin with S1 and extend for a variable period of time, ending well before S2. Their causes are relatively few in number. Acute severe MR into a normal-sized, relatively noncompliant left atrium results in an early, decrescendo systolic murmur best heard at or just medial to the apical impulse. These characteristics reflect the progressive attenuation of the pressure gradient between the left ventricle and the left atrium during systole due to the rapid rise in left atrial pressure caused by the sudden volume load into an unprepared chamber, and contrast sharply with the auscultatory features of chronic MR. Clinical settings in which acute, severe MR occur include: (1) papillary muscle rupture complicating acute myocardial infarction (MI) (Chap. 239), (2) rupture of chordae tendineae in the setting of myxomatous mitral valve disease (MVP, Chap. 230), (3) infective endocarditis (Chap. 118), and (4) blunt chest wall trauma.