Purpose: This study aims to evaluate a method to detect heart rate variability (HRV) changes using short ECG segments during ablation for arrhythmias.
Methods: HRV was averaged from sequentially shorter time windows from 5-min ECG recordings in 15 healthy volunteers. The 40-s window was identified as the shortest duration that yielded reproducible values in high frequency (HF) and low frequency (LF) HRV. This method was validated in patients undergoing tilt table testing to see if the expected modulation in HRV that occurs prior to syncope could be detected from multiple 40-s recordings. Lastly, this method was used to assess HRV changes in 75 patients undergoing ablation for atrial fibrillation (AF) and other arrhythmias, to see if autonomic modulation as a result of ablation could be detected. A further 14 patients had stepwise HRV measurements at different stages of the AF ablation procedure to determine whether intra-procedural HRV changes could be detected.
Results: HRV, averaged from multiple 40-s recordings, demonstrated the expected increase immediately preceding syncope compared with baseline (LF: 341 ± 311-1,536 ± 1,368 ms(2), p< 0.05; HF: 342 ± 339-1,628 ± 1,755 ms(2), p < 0.05). AF ablation, particularly following right pulmonary vein circumferential ablation, produced immediately detectable reductions in LF (153 ± 251-50 + 116 ms(2), p < 0.001) and HF (86 ± 195-33 ± 83 ms(2), p < 0.001) without any change in RR interval (877 ± 191-843 ± 220 ms, p = 0.261). Ablation for atrial flutter did not change the mean RR interval, LF or HF HRV.
Conclusion: Averaging multiple 40-s windows give valid HF and LF HRV measurements that enable detection of intra-procedural changes. Left atrial ablation around the right-sided pulmonary veins is unique in producing reductions in HRV. This method has the potential for use as an endpoint marker for adjunctive autonomic ablation procedures.