Double Atrial Sounds and Peripheral Atrial Impulses in a Patient with Complete Heart Block

Abstract

Distinct double atrial sounds and atrial impulses transmitted to peripheral arteries were recorded in a 65-year-old man with heart block. The 1st atrial sound occurred 0.10 seconds after onset of atrial depolarization and the 2nd after 0.24 seconds. Atrial sounds were not recorded during ventricular systole but when atrial systole occurred immediately prior to ventricular depolarization the atrial sound fused with the 1st heart sound so that the resultant sound was intensified. Transmitted atrial impulses which were recorded over peripheral arteries appeared approximately 0.16 second after the onset of atrial depolarization. Since the atrial impulses were abolished by a pressure of 100 mm Hg, it is suggested that they were transmitted mechanically and were not of a neuromuscular origin.