Effect of procainamide and lidocaine on total electrical systole of ventricular premature depolarizations.

The effect of lidocaine and procainamide on the electrocardiogram of a patient with coupled ventricular premature depolarizations was observed after continuous electrocardiographic monitoring during a control period and drug therapy. First lidocaine, 100 mug/kg/min, and 3 1/2 hours later procainamide, 200 mug/kg/min, were infused until the arrhythmia was completely suppressed. In each drug study, blood samples were taken every 5 minutes for determining plasma drug concentration. In addition to important differences between the two drugs on the standard electrocardiographic intervals, a new electrocardiographic phenomenon was recognized: a change in the total electrical systole of the ventricular premature depolarization (ventricular premature depolarization-Q-T interval). These observations are discussed and related to the electrophysiologic properties reported for each of these agents.