Catheter ablation for septal accessory pathways is occasionally associated with complications, such as atrioventricular block, since the septal region is a complex anatomical structure containing the atrioventricular conduction system. Therefore, we designed a signal separator composed of an inductancecapacitance network with which the local electrogram at the ablation site could be continuously monitored during the delivery of radiofrequency (RF) energy. We tested the safety and efficacy of RF catheter ablation using a signal separator in 17 patients with septal accessory pathways (10 anteroseptal and 7 midseptal cases). RF energy (520KHz) was applied at an output of 20-40W for 30-120sec. to the atrioventricular annulus where the shortest atrioventricular interval or accessory pathway potential was recorded on the electrogram using a large tip ablation electrode. In ablation for the anteroseptal or midseptal accessory pathways, the atrial to ventricular amplitude ratio on the local electrogram was maintained at 1 or less during the delivery of RF energy. In all 17 cases, the interruption of accessory pathways was successful without atrioventricular block. In one patient, accessory pathway conduction recurred which could be treated by the second session. There were no late complications during the 4 to 46 month follow-up period.
In conclusion, RF catheter ablation using a signal separator is a safe and reliable method for treating patients with septal accessory pathways.