AbstractFourteen patients with paroxysmal supraventricular tachycardia (PSVT) underwent serial electrophysiologic studies using transesophageal atrial pacing (EPS‐EP), to determine the predictive value of this method in the selection of antiarrhythmic therapy and to study the mechanism of the tachycardia.In each patient, PSVT could be reproducibly initiated by burst and/or programmed stimuli. After control EPS‐EP, the effects of several drugs (diltiazem, disopyramide, propranolol, digoxin, procainamide and verapamil) on the ability to initiate PSVT or to bring about “tachycardia zone” were examined. The mechanisms of PSVT were also investigated using an esophageal electrode, EPS‐EP, and Ca++‐antagonists.Drug responses were variable but in most cases tachycardia could not be initiated after drug administration. Four types of supraventricular tachycardia are described. In eight out of nine patients, good therapeutic control was obtained. This study shows that serial EPS‐EP can provide rapid identification of appropriate antiarrhythmic therapy, and is useful in studying the mech