Manner of Stimulus Conduction in Atria

Abstract

The manner of the stimulus conduction was investigated for both left and right atria of the canine heart through analysis of the configuration of unipolar ecg and the arrival times of the activation wave. Langendorff''s method of irrigating the heart was used. In the right atrium, the stimulus spread from the S-A [sino-auricular] node to the orifice of the I.V.C [inferior vena cava] with higher conduction velocity along the sulcus terminalis. The stimulus coming along the sulcus terminalis spread over the atrium through the muscle bundles which branched from the sulcus terminalis. The apex of the atrial appendage was the last portion to become activated. In the left atrium, the stimulus originating in the S-A node, spread through Bachmann''s bundle, 1st. The stimulus coming along Bachmann''s bundle spread over the atrium through the muscle bundles which branched from Bachmann''s bundle. The region between the left lower pulmonary vein and the A-V [atrio-ventricular] ring was activated last in both left and right atrium. In some cases, there was an area in which the stimulus originating in the S-A node might reach directly from the right atrium without passing through Bachmann''s bundle. This area was located in a small region of the postero-inferior portion of the left atrium near the I.V.C.