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 electrophysiologic properties, and an effective radiofrequency catheter ablation technique in patients with septal accessory pathways.

PATIENTS

Forty-six consecutive subjects with septal accessory pathways located in the anteroseptal, midseptal, and para-Hisian areas.

DESIGN AND INTERVENTIONS

ECGs obtained during sinus rhythm and orthodromic tachycardia, conduction properties obtained from electrophysiologic study, and results of two different ablation techniques were analyzed.

MEASUREMENTS AND 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 negative delta wave in lead III and a biphasic delta wave in lead aVF during sinus rhythm, and a negative retrograde P wave in two inferior leads during orthodromic tachycardia; (2) midseptal pathways had better antegrade conduction properties and a significantly higher incidence (61.5%) of inducible atrial fibrillation; (4) radiofrequency catheter ablation using lower energy (20+/-6 W) had a comparable effect to ablation using higher energy (36+/-5 W), but without impairment of atrioventricular (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 pathways had ECG and electrophysiologic characteristics that were distinctive from those of anteroseptal and para-Hisian pathways. Catheter ablation of these septal pathways using low radiofrequency energy was safe and effective.