Propagation of impulses through the atrioventricular node

Abstract

Records taken from the bundle of His and A-V node region of isolated and perfused dogs' hearts showed an action potential (N potential), which appeared after the auricular response and preceding the electrogram of the bundle of His (H potential). The H potential may disappear without affecting the N potential and the latter may be abolished while the auricular electrogram is still present. These observations permit the interpretation that the N potential is generated independently. The temporal course and the time of occurrence of the N potential, indicate that it represents the activity of the A-V node. The N potential divides the A-H interval into A-N and N-H latencies. Progressively increasing frequencies of activation of the auricle lengthened first the N-H latency until the H potential disappeared. Higher frequencies lengthened the A-N latency until the N potential also disappeared. In order to explain the experimental findings, it is suggested that there are two functional discontinuities, one located between the A-V node and the bundle of His, and the other between the atrium and the A-V node; the first is the most vulnerable for propagation.