S4 and acute left sided valvular regurgitations

S4 and acute left sided valvular regurgitations

S4 is never heard in acute aortic regurgitation while it is heard in acute mitral regurgitation. Mitral valve pre-closure occurs in acute aortic regurgitation. Hence S4 does not occur in acute aortic regurgitation. Mitral valve pre-closure in acute aortic regurgitation is due to the high left ventricular end diastolic pressure.