Evolving modes of energy delivery for catheter ablation of accessory pathways.

R ecognition of the possibility of ablating cardiac tissue by means of commonly used electrophysiological catheters has led to the development of the fulguration techniques. Unipolar DC (direct current) shocks delivered at the tip of a catheter by means of an ordinary defibrillator were applied to the atrioventricular node-His bundle area for control of refractory supraventricular tachycardias. This technique was then rapidly extended to other cardiac areas, among which is that of the accessory pathway. Because of its easy access and because of the excellent initial results, high-energy DC shocks initially appeared more suitable for all types of ablation than did radiofrequency alternating current.1-3 However, morbidity and probably long-term mortality of DC shocks were significant, and this was probably due to arcing and barotrauma at the site of energy delivery.4-6 This has stimulated research for a new energy source that could yield the same good results as that of high-energy fulguration yet remaining as safe as radiofrequency current. Based on the concept that voltage and current density rather than barotrauma were responsible for tissue ablation, British workers designed a new ablation system that uses a low-energy power supply connected to a special contoured electrode.7 In vitro and in vivo testing confirmed both effectiveness and lack of deleterious effects of low-energy DC shocks. This has also been shown to have no deleterious effects on dangerous locations such as the coronary sinus.8