Phonocardiogram of aortic regurgitation as heard at the apex

Carotid artery pulse tracing and phonocardiogram of aortic regurgitation as heard at the apex. There is a fourth heart sound (S4) heard prior to S1 (mitral and tricuspid valve closure) and the upstroke of the carotid arterial pulses. This is the result of atrial contraction into the "stiffened" left ventricle. Following S1 is a short systolic ejection murmur that results from the large stroke volume seen in aortic regurgitation.