Transient Ventricular Conduction Disturbances Produced by Intra-atrial Injection of Single Doses of KCI

In dogs under pentobarbital anesthesia, the administration of KCl in single intra-atrial doses of 1 mg/kg produced varying effects on intraventricular conduction depending upon the initial potassium concentration of systemic blood. At normal and moderately increased systemic K concentrations, single injections of KCl improved intraventricular conduction, but at higher systemic K concentrations a negative dromotropic effect appeared. Following injection into the right atrium, the effect appeared immediately in the right ventricle, followed after some delay by an appreciably lesser effect in the left ventricle. Injection of potassium into the left atrium altered conduction in the left ventricle without affecting the right ventricle. The results indicate that transient alterations of K in the blood of the ventricular cavity can act directly on the specialized conduction network to alter the rate of intraventricular conduction.