Audibility of the Fourth Heart Sound

To determine the meaning of an audible fourth heart sound (S4), 51 subjects (21 normal and 30 abnormal persons), aged between 38 and 74 years (mean, 55.4 years), were examined by nine "blinded" physicians (four cardiologists, five house staff officers). Audibility scores were compared with phonocardiographic, echocardiographic, and hemodynamic measurements. An S4 was recorded graphically in 35 (68.6%) of all 51 subjects and splitting of the first sound (S1), in 37 subjects (72.5%). The abnormal group did not differ significantly from the normal subjects in incidence of recordable S4 or splitting of S1. Audibility of S4, however, correlated with its recorded amplitude, size, and palpability of the presystolic apical impulse, left ventricular systolic and diastolic diameters, and history of myocardial infarction. Despite variation among examiners, house staff officers were likelier than cardiologists to believe an S4 present even in cases lacking a recordable S4 and in normal subjects and were more apt to believe an S4 present when splitting of S1 was identified graphically. We conclude that an audible S4 continues to provide evidence for cardiac disease, and that increasing examiner experience renders this finding fairly specific. Less experienced examiners are likelier to confuse splitting of S1 with the S4, suggesting that training should be focused on means to improve this differentiation.