 These electrophysiological changes decrease the sensitiveness of cells to electrical stimuli, which leads to an increase in action potential duration and an increase in the effective refractory period.By increasing the effective refractory period NAPA is very useful in suppressing tachyarrhythmias caused by re-entry ventricular arrhythmia.In this way NAPA can increase the Q - T interval of the PQRST heart rhythm.