The Significance of Changes in Amplitude of the First Heart Sound in Children with A-V Block

Abstract

Curves which relate the peak intensity of the first heart sound to the P-R interval have been obtained from seven children with complete A-V block. The first sound is accentuated with short P-R intervals, becomes faint when the P-R interval is in the neighborhood of 0.20 to 0.30 second, and becomes loud again with relatively long P-R intervals. Repeated observations over a number of years demonstrated the effects of growth and aging on these phenomena. The data appear to indicate that the variable intensity of the first sound in complete A-V block is related to the position of the mitral valve at the time of ventricular systole.