Localization of the initial fibrillatory cycle in patients with paroxysmalatrial fibrillation

Background - Recent reports suggest the presence of conduction delay in the posterior septal region during sinus rhythm in patients with lone paroxysm al atlial fibrillation (AF). Objective - To explore the location of intra-atrial conduction delay associ ated with initiation of AF. Design - In 8 lone AF patients (51 +/- 10 years), 20 AF paroxysms were indu ced during electrophysiological examination. Bipolar electrograms were acqu ired from a 10-polar catheter in the coronary sinus (CS), a 4-polar His bun dle catheter, and a 20-polar Halo catheter in the right atrium. Results - Induced AF paroxysms showed earliest registered atrial activity i n interatrial septum (IAS) or proximal CS in 17 cases (85%). Conduction del ay at the posterior IAS or proximal CS accompanied induction of 18 AF parox ysms (6 patients). Atrial activation sequence at the beginning of the AF pa roxysms was stable and reproducible in six repeatedly induced AF episodes ( 3 patients). Conclusion - In lone AF patients, induction of AF is associated with conduc tion disturbances in the IAS and proximal CS regions.