THE ELECTROCARDIOGRAM OF NON-ANESTHETIZED DOGS AS MODIFIED BY THE INTRAVENOUS INJECTION OF PITRESSIN, ATROPINE SULPHATE AND VAGUS SECTION

¹ From the Departments of Pharmacology and Internal Medicine, Washington University, School of Medicine, Saint Louis, Missouri

1. In non-anesthetized dogs, pitressin injected intravenously causes very definite cardiac changes: (a) A brief period of slowing; (b) a brief period of acceleration; (c) a prolonged period of profound slowing. During this phase, electro-cardiographic curves show shifting pacemaker, prolongation of the auriculoventricular conduction time, sino-auricular block, partial auriculoventricular block, extra systoles, high T-waves, high branching T-waves and bigeminal pulse.

2. After atropine or after vagus section, pitressin produces the same cardiac changes except that the decrease in heart rate is not as great nor is the acceleration as pronounced.