Occurrence of atrial fibrillation after flutter ablation: the significance of intra-atrial conduction and atrial vulnerability.

Atrial vulnerability and intra-atrial conduction delay are important substrates for paroxysmal atrial fibrillation (AFib); however, their significance is unknown in patients undergoing atrial flutter ablation. Antegrade (high right atrium to coronary sinus: HRA-CS) and retrograde (CS-HRA) intra-atrial conduction times and AFib inducibility were assessed in 61 patients undergoing ablation for type I atrial flutter. Twenty-three patients had structural heart disease and 18 AFib before the procedure. After 16 +/- 12 months of follow-up 17 patients experienced AFib, 5 of which progressed into chronic AFib. During the study, AFib was easily inducible in 14 patients, 7 of which developed AFib (P =.03). Patients with post- ablation AFib were older (59 +/- 11 vs. 44 +/- 15 years, P =.001), had longer intra-atrial conduction times before (98 +/- 17 ms vs. 68 +/- 20 ms, P <.001) and after ablation (91 +/- 19 ms vs. 73 +/- 21 ms, P =.01) than those without AFib. Discriminant analysis revealed that only age, previous AFib and inta-atrial conduction delay (>90 ms) were independent predictors of postablation AFib. Patients without a history of AFib and with normal intra-atrial conduction had a 3% risk of AFib, while patients with both factors had a 90% risk of AFib after ablation. Intra-atrial conduction delay is an important electrophysiological factor predicting atrial fibrillation after successful flutter ablation.