Prolongation of ventricular action potential due to sympathetic stimulation

The changes of monophasic action potential durations due to stellate stimulation for the period of 3 sec were studied in dogs with suction electrodes from the anterior surface of the right ventricle and the posterior surface of the left ventricle. Prolongation of monophasic action potential duration was observed from the period of 2 to 3 sec during stimulation to that of 10 to 20 sec after the termination of stimulation. Prolongation of monophasic action potential duration due to right stellate stimulation was predominant in the right ventricle and that due to left stellate stimulation was predominant in the left ventricle. The transient T wave change in the surface electrocardiogram occurring immediately after the beginning of stellate stimulation could be explained by this local difference in prolongation of ventricle repolarization. Since the onset of prolongation of monophasic action potential duration preceded increase in blood pressure following stellate stimulation, this prolongation of monophasic action potential duration did not result from the hemodynamic changes and could be a primary effect of the sympathetic nerve stimulation.