Importance of vagal tone before atrial fibrillation onset

Neuromodulation is increasingly attempted during ablation procedures for atrial fibrillation (AF). The role of the cardiac autonomic nervous system (CANS) in triggering paroxysmal AF episodes is well-established. Heart rate variability (HRV) provides information on the final output of the influence of the CANS. The high frequency component (HF: 0.15–0.40 Hz) reflects vagal activity, and the low frequency component (LF: 0.04–0.15 Hz) reflects a complex mix of parasympathetic, sympathetic, and other unidentified non-linear factors. Therefore, clinically, the analysis of the temporality of these parameters could be useful for the selection of additional therapy during AF ablation procedures. Study the significance of CANS variations prior to AF onset by tracking the evolution of frequential parameters of HRV and premature atrial contractions (PACs). We screened our ECG Holter monitoring database of more than 20,000 patients to find those with paroxysmal AF episodes recorded. Three hundred analyzable AF onsets from 210 paroxysmal AF patients were labelled. We analyzed HRV frequential parameters by segments every 300 RR intervals, progressing beat by beat to allow the evolution of the spectral parameters of the HRV and count of PACs to be closely monitored. We focused on the evolution of low (LF) and high frequencies (HF), as well as the LF/HF ratio and the number of PACs. We observed several cyclical variations of increasing amplitude in CANS followed by a final significant upward shift in HF and LF preceding the onset of AF. The number of PACs shows a progressive increase in parallel to autonomic changes (see Fig. 1 ). These data suggest that vagal influence is preponderant in the AF onset for most of the patients. This is in favor of a thoracoscopic approach to neuromodulation procedures, as ganglionic plexi contain mainly parasympathetic neurons and are located in epicardial fat pads.