The effect of procainamide on delayed activation potentials in a patient with ventricular tachycardia

In a patient with ventricular tachycardia and previous myocardial infarction, delayed activation potentials were recorded from a region of the posterolateral wall of the left ventricle at electrophysiological study. Procainamide, administered intravenously, initially caused increased delay and later, in higher dosage, second-degree block of the delayed potentials.