Effects of antikaliuretic agents on cardiac electrophysiology--measurements in papillary heart muscle and in purkinje fibers.

Electrophysiological parameters of myocardial excitability of heart muscle in vitro were studied under the influence of antikaliuretic diuretics. Potassium canrenoate, amiloride and triamterene were added in final concentrations of 5-440 mug/ml incubation medium. Resting and action potentials as well as refractory periods of single muscle cells and Purkinje fibers were measured by the microelectrode technique.--The antikaliuretic substances potassium canrenoate, amiloride and triamterene led to a significant concentration-dependent prolongation of action potential duration and, correspondingly, to a lengthening of the refractory period. Glycoside-induced shortening of the refractory period could be demonstrated to be antagonized by triamterene.--Results suggest that aldosterone antagonists, amiloride and triamterene may exhibit antiarrhythmic properties in the ventricular myocardium as well as in the conducting tissue. Drugs are equally effective when compared in molar concentrations. The application of antikaliuretic diuretics seems to be useful in the therapy of congestive heart failure with respect to their extrarenal cardiac effects, too.