[Disorders in automatism and atrioventricular conduction during Luciani periods]

In isolated perfused hearts of rabbits and in spontaneously active preparations of the Purkinje fibers, conditions for occurrence of Luciani's periods were studied. Hypoxia, inhibitors of energy metabolism, inhibitor of the membrane Na+, K+ - ATPase ouabain, and acetylcholin were shown to induce primarily disturbances of the intracardiac conduction up to complete atrioventricular blockade in isolated hearts, periodic asystolia of ventricles occurring under these conditions only. With the aid of microelectrode recording of transmembrane potentials, Luciani's periods were found to be a periodic suppression of the Purkinje fibers' automatism. As distinct from the ventricles, no Luciani's periods occur in atria which indicates functional stability of the nomotopic pace-maker of the heart: the sino-atrial node.