DIRECTIONAL DIFFERENCES IN THE CONDUCTION OF THE IMPULSE THROUGH HEART MUSCLE AND THEIR POSSIBLE RELATION TO EXTRASYSTOLIC AND FIBRILLARY CONTRACTIONS

Abstract

It was demonstrated that under certain conditions turtle ventricular strips conduct better in one direction than in the other; under severe conditions unidirectional block may occur. Such blocks have been produced following compression, passage of strong polarizing currents and by variation of the ionic balance of the Ringer solution locally applied. The Engelmann correlation between speed of conduction and relative irritability could not be confirmed. It is suggested that the Mines theory of A-V monodromia attributing the condition to an asymmetric decremental conduction in a depressed region be modified to include as additional variables strength of impulse and irritability of the responding side. Under certain conditions phenomena of re-entry were observed. An explanation of the phenomena based upon conduction data is offered which attributes the re-entry to the establishment of a mono-dromic condition in certain of the fiber paths. Also based upon such a local monodromia in an ultimate twig of the conduction system, an explanation is offered of the mechanism of the coupled type of ventricular response. Finally it is shown how a slight modification of the conditions that produce re-entry would lead to the establishment of local circus contractions, and the relation of circus contractions so produced to tachycardia, flutter, and fibrillation is discussed.