Intra-atrial conduction delay and fragmented atrial activity in patients with paroxysmal atrial fibrillation.

To examine the electrophysiologic characteristics of paroxysmal atrial fibrillation (PAF), we studied intra-atrial conduction delay and fragmented atrial activity during premature stimulation of high right atrium in the following four groups: Group I (n = 25), patients without PAF and without sick sinus syndrome (SSS); Group II (n = 22), patients with PAF but without SSS; Group III (n = 10), patients without PAF and with SSS; Group IV (n = 6), patients with PAF and SSS. Intra-atrial conduction delay was the increase in the interval (from the stimuli to the coronary sinus electrogram) observed with early premature beats greater than or equal to 20 ms compared with that of basic rhythm. Fragmented atrial activity was defined as disorganized atrial activity greater than or equal to 150% of the duration of high atrial activity of basic beats recorded. The conduction delay zone (CDZ) and fragmented atrial activity zone (FAZ) were significantly wider in Groups II, III and IV than in Group I. There were no significant differences in either CDZs or FAZs among Groups II, III and IV. Thus, the widening of CDZs and/or FAZs are characteristic of PAF and SSS. CDZ and FAZ may be good indices of development of PAF in patients without SSS.