Sympathetic Responses Induced by Radiofrequency Catheter Ablation of Atrial Fibrillation.

Radiofrequency catheter ablation (RFCA) is a frequently performed procedure in patients with atrial fibrillation. Prior studies have shown that the RFCA may directly stimulate vagal afferents during the procedure, while the vagal tone assessed by heart rate variability (HRV) is lowered weeks post the RFCA procedure. The effects of RFCA performed in the left atrium on sympathetic nerve activity has not been assessed. In this study, we hypothesized that RFCA would lower muscle sympathetic nerve activity (MSNA) during ablation and would raise MSNA one day post-ablation. A total of 18 patients were studied. In Protocol 1 (n = 10), the ECG, blood pressure and MSNA in the peroneal nerve were recorded through the RFCA procedure performed in the electrophysiology laboratory. In Protocol 2, eight patients were studied before the procedure and one day post-ablation. RFCA led to a decrease in MSNA immediately post the procedure (25.4 ± 3.2 to 17.2 ± 3.8 bursts/min, P < 0.05). Cardiac parasympathetic activity determined using indices of HRV increased during the procedure. One day post-ablation, MSNA was above the baseline values (21.3 ± 3.7 to 35.7 ± 2.6 bursts/min, P < 0.05). HRV indices of cardiac parasympathetic activity fell, and the HRV index of sympathovagal balance was not significantly altered. The results show that RFCA raised cardiac parasympathetic activity and decreased MSNA during the procedure. One day post-ablation, MSNA rose, cardiac parasympathetic activity fell. In addition, RFCA evokes differentiated sympathetic responses directed to the heart and to skeletal muscles.