Effects of aprindine on monophasic action potentials

Using a catheter electrode developed by the authors for recording monophasic action potentials (MAPs), the atrial and ventricular MAPs of seven mongrel dogs were simultaneously recorded. The results were used to evaluate the effect of the new antiarrhythmic drug aprindine on MAPs. An electrophysiologic study was also carried out to evaluate the effect of aprindine on the conduction system. Aprindine caused a significant increase in both the AH interval (at a basic cycle length of 400 ms) and the HV interval (at basic cycle lengths of 400 and 500 ms). The effective refractory period increased in both the right atrium and the right ventricle. Although an increase in MAP duration at repolarizations to 90% MAP (MAPD90) was not observed in the right atrium, a significant increase was noted in MAPD90 in the right ventricle. There were no significant changes in the ratio between the effective refractory period and MAPD90 of the right ventricle before and after administration of aprindine. This result suggests that increases in MAPD90 contribute to an increase in the effective refractory period of the right ventricle.