Cardiac tachyarrhythmias that are refractory to either conventional or experimental antiarrhythmic therapy, antitachycardia pacemakers, or both, may result in serious symptoms or death. Catheter ablation has been developed as a nonpharmacologic, closed-chest alternative for the management of these patients. The technique was first applied to man in 1981 and reported by both Scheinman et al and Gallagher et al in 1982. Hartzler reported the first catheter ablation procedure for the treatment of ventricular tachycardia in 1983. In that same year, Weber reported the first use of catheter ablation of an accessory atrioventricular pathway. The standard method of energy delivery for closed-chest catheter ablation attempts involved direct current delivered using a defibrillator, but beginning in 1985, radiofrequency energy was employed in man. This promised to revolutionize the field of catheter ablation, because it offered the hope of more precise destruction of tissue, avoided the need for general anesthesia and significantly lowered complication rates, since it did not involve the levels of energy used in direct current attempts.