Audibility of the Fourth Heart Sound

Abstract

An auscultatory search for a fourth heart sound (S₄) was performed by two independent "blind" auscultators who did not know the medical status of 196 consecutively examined subjects, ages 50 to 80 years. Phonocardiograms (PCGs) and other tracings taken after recording the results were measured by a third observer who was also "blind." Results of this investigation indicate that any tendency for rapid completion of atrial excitation and early onset of S₄appears to determine the auscultatory audibility of the fourth heart sound. Conversely, a tendency to later completion of atrial excitation and a later onset of S₄will make it auscultatorily inaudible, although recordable even at considerable amplitude by PCG. The relative amplitude and frequency of S₄were not significantly related to its audibility. The presence or absence of disease was not significantly related to the presence or absence of S₄by PCG or to its audibility when present.