Effects of disopyramide on repolarisation and intraventricular conduction in man

Right ventricular repolarisation and refractoriness after therapeutic doses of disopyramide have been studied in 10 patients with coronary artery disease by recording monophasic action potentials (MAP) during programmed stimulation. Using 2 catheters, with the tip of one in the apex and the other in the outflow tract of right ventricle, conduction intervals for propagation of stimuli in the ventricle were also measured. Disopyramide increased the duration of MAP signals at 90% repolarisation (MAP90), the QT-interval and the right ventricular effective refractory period (V-ERP). The ratio refractoriness/action potential duration was slightly increased. Early premature action potentials were more markedly prolonged in relation to steady-state action potentials. The differences between the shortest and longest premature action potentials, however, were not changed significantly. The conduction intervals of the normal and premature paced beats were significantly prolonged. The observed effects of disopyramide on conduction and action potential duration may be of major importance for its effect on termination and slowing ventricular tachycardias. Its influence on the duration of premature action potentials in man is consistent with the results of in vitro studies.