STUDIES ON THE APPEARANCE AND TERMINATION OF ACONITINE-INDUCED ATRIAL FIBRILLATION WITH MICROELECTRODES

Abstract

Aconitine-induced fibrillation was studied on the right atrium isolated from a young rabbit, and the electrical activity from 2 fibers was traced simultaneously in order to clarify the mechanism of the appearance and termination of the fibrillation. The administration of aconitine (0.8[long dash]1.5x10-6) was followed first by an acceleration and fluttering of the atrial activity, and next by the formation of local blocks and disturbance of the spread of sinus rhythm. An irregular fluctuation and increased dispersion in size of the resting potential were produced resulting in nonsynchronized local or abortive activities of the cells and a temporal fibrillation which finally ceased. Reintroduction of the normal solution induced the formation of 1 or more ectopic pace-makers. The activity was intermittent at first, waxing and waning, and occurred one after another or one with another. These states gradually developed into a typical fibrillation which continued a few hours. During the fibrillation, no definite circus movement was observable mainly due to the uninterrupted variation in activity of each fiber and the frequent occurrence of pace-maker shift. In the course of recovery from the fibrillation, synchronism in activity of each fiber, full magnitude of the action potentials, and their uniformity in shape and rhythm were gradually restored with disappearance of local blocks. It was estimated that the formation of local blocks and ectopic pace-makers might be principal factors in the development of atrial fibrillation.