Effect of Artificially Controlled Heart Rate on the Incidence of Ventricular Fibrillation in Hypothermia

¹ From the Department of Physiology, Boston University School of Medicine, Boston, Massachusetts

Five dogs were subjected to auricular and five to ventricular driving throughout the period of cooling. All animals in both groups succumbed to ventricular fibrillation at mean temperatures of 21.3°C and 20.3°C, respectively. These temperatures do not differ significantly from those for dogs with spontaneous heart action. Thus, abnormalities in S-A nodal rhythm or A-V conduction appear not to be contributory to fibrillation, since the one is eliminated by auricular driving and the other by ventricular driving. Intraventricular conduction times were assumed equal to the QRS duration. In both groups the conduction time increased linearly over the temperature range studied, and the slopes were parallel, suggesting that the limiting, temperature-sensitive process in conduction is the same for Purkinje system and myocardium.