Radiofrequency ablation of a slow pathway in AV-nodal tachycardia.

A 35-year-old woman with frequent attacks of paroxysmal supraventricular tachycardia and psychiatric background was submitted to ablation of AV-nodal tachycardia. Before ablation, tachycardia with a cycle length of 455 ms was easily induced with regular atrial stimulation or with one extrastimulus. Radiofrequency current (35 Watts) was applied on a site, localized between the His bundle and the ostium of the coronary sinus. The local electrogram showed an atrial activation 20 ms before the atrial activation at the His bundle site during tachycardia. Application terminated AV-nodal tachycardia within 2.5 seconds. Two back-up applications were given during sinus rhythm. At the control study, conduction over the slow pathway was abolished, and the fast conduction remained intact with a Wenckebach 2:1 block point at 180 beats/min. She remained free of recurrences with a follow-up of more than 3 months. The possibility of selective ablation of the slow pathway in AV-nodal tachycardia is discussed.