Determinants of Atrial (S4) and Ventricular (S3) Gallop Sounds in Primary Myocardial Disease

Clinical, hemodynamic and angiographic correlates in 23 patients with primary myocardial disease and either atrial (S4) or ventricular (S3) gallop sounds differentiated the two groups. Those with S4 gallop had normal mean left atrial pressures, low amplitude "v" waves, small drop from "v" to "y", usually reduced v/y slope, prominent "a" kick, abnormal echocardiogram of mitral valve, nearly normal cardiac output and marked left ventricular hypertrophy. In contrast the S3 group had elevated mean left atrial pressures, tall "v" waves and large drop from "v" to "y", with increased v/y slope, no prominent "a" kick, rapid filling on the echocardiogram, reduced cardiac output and left ventricular cavitary dilatation. Atrial gallop sound can thus be explained by ventricular hypertrophy, causing reduced compliance and increased resistance to filling, with augmented atrial boost and gallop, whereas considerable ventricular dilatation, with reduced cardiac output, elevated filling pressure and augmented early filling may produce ventricular gallop.