Electrophysiological Evidence of the Initiation of Arrhythmia by Beta-Adrenergic Blocking Agents

Abstract

In 1967 the author (1) mentioned the alternate occurrence of the action potential of the spike type and the one of the spike-and-dome type from the canine Purkinje fibers exposed to a high concentration of magnesium ions. Concurrently Matsuda et al. (2) observed that procaine and low external sodium concentration produced the alternation of the spike type action potentials and the spike-and-dome type from the terminal Purkinje fibers of the dog, which resulted in the partial or complete block of the Purkinje fiber-ventricular muscle conduction. The Purkinje-ventricular delay time is reported also to be increased by hypothermia (2) or low external calcium (3). Sasyniuk and Mendez (4) made it clear that at the Purkinje-muscle junctions the re-entrant beat may emerge as an extra-systole and this event may be facilitated by the electrotonic shortening of action potentials of Purkinje fibers at relatively long distances from the site of conduction block.