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 electrophysio-logical study. Procainamide, administered intravenously, initially caused increased delay and later, in higher dosage, second-degree block of the delayed potentials.