ELECTROCARDIOGRAPHIC AND ELECTROPHYSIOLOGIC CHARACTERISTICS OF ANTEROSEPTAL, MIDSEPTAL, AND PARA-HISIAN ACCESSORY PATHWAYS - IMPLICATION FOR RADIOFREQUENCY CATHETER ABLATION

Study objective: To investigate the ECG characteristics, the electroph ysiologic properties, and an effective radiofrequency catheter ablatio n technique in patients with septal accessory pathways. Patients: Fort y-six consecutive subjects with septal accessory pathways located in t he anteroseptal, midseptal, and para-Hisian areas. Design and interven tions: ECGs obtained during sinus rhythm and orthodromic tachycardia, conduction properties obtained from electrophysiologic study, and resu lts of two different ablation techniques were analyzed. Measurements a nd results: (1) Twenty-four (52.2%) had manifest preexcitation and 15 (32.6%) had multiple accessory pathways; (2) midseptal pathways could be differentiated from anteroseptal and para-Hisian pathways by a nega tive delta wave in lead III and a biphasic delta wave in lead aVF duri ng sinus rhythm, and a negative retrograde P wave in two inferior lead s during orthodromic tachycardia; (3) midseptal pathways had better an tegrade conduction properties and a significantly higher incidence (61 .5%) of inducible atrial fibrillation; (4) radiofrequency catheter abl ation using lower energy (20+/-6 W) had a comparable effect to ablatio n using higher energy (36+/-5W), but without impairment of atrioventri cular (AV) node conduction or development of AV block; and (5) during the follow-up period of 26+/-14 months (range, 5 to 54 months), three (6.5%) patients had recurrence. Conclusions: Midseptal accessory pathw ays had ECG and electrophysiologic characteristics that were distincti ve from those of anteroseptal and para-Hisian pathways. Catheter ablat ion of these septal pathways using low radiofrequency energy was safe and effective.