Effects of encainide on myocardial contractility of cat papillary muscle.

The action of a new effective antiarrhythmic agent, encainide, was studied with respect to the mechanical performance of isolated cat papillary muscle. Encainide (0.1-10 micrograms/ml) did not alter the performance of cardiac muscle during either the contraction or relaxation phase. By contrast, lidocaine (1-5 micrograms/ml) caused a slight but statistically significant depression of myocardial contractility in terms of the force-velocity-length analysis, while it did not affect load clamp analysis, zero load clamp analysis and load dependence of relaxation.