Analysis of Heart Rate Variability before and after Catheter Ablation for Atrial Flutter with Complicating Atrial Fibrillation

Efficacy of radiofrequency (RF) catheter ablation in suppressing atrial fibrillation (AF) was studied by analysis of heart rate variability (HRV) in 13 patients with atrial flutter complicated with AF. We treated these patients by RF ablation of the isthmus between the tricuspid valve annulus and the inferior vena cava to create a bidirectional conduction block. To analyze the HRV, 24-h ambulatory electrocardiographic monitoring was performed 1 day before, 1 day after and 1 month after the ablation. After the RF ablation of the isthmus, 7 patients continued to experience AF attacks, while the remaining 6 patients did not. We divided them into 2 groups, attacked by AF (AF group) and not attacked by AF (non-AF group), and analyzed HRV parameters. The results obtained were compared between the groups. One month after the ablation, the non-AF group showed a significantly higher average heart rate than the AF group. The HRV parameters indicating cardiac vagal nervous activities, such as the root-mean-square of differences, percentage of adjacent normal RR intervals and high frequency power, were significantly lower in the non-AF group 1 month after. Furthermore, the ratio of low frequency power to high frequency power, which is a measure for cardiac sympathetic nervous activity, was significantly higher in the non-AF group 1 month after. From these results, we postulate that the suppression of postoperative AF may involve vagal nerve suppression and sympathetic nerve activation.