Dynamic change, not tonic activation, of the heart rate variability predicts onset of postoperative atrial fibrillation

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Abstract Background and Aims Post-operative autonomic disturbances contribute to susceptibility to post-operative atrial fibrillation (POAF) but the nature of the autonomic disturbances and whether they precede POAF and can signal POAF onset is unclear. Methods In this prospective observational study, patients undergoing cardiac surgery were consecutively enrolled. Holter monitoring was undertaken 7 days before and after surgery with continuous heart rate variability (HRV) measurement. Cox regression was used to evaluate autonomic changes, and analyzed by restricted cubic spline (RCS) to explore individual risk levels. For the first episode of POAF, HRV indexes captured an hour before the onset of POAF were divided into six 10-minute epochs and analyzed by Friedman's Two-Way Analysis of Variance by Ranks. Results A total of 2306 patients known to have been without prior AF were enrolled and completed the study; POAF occurred in 718 (31.14%) patients. Based on univariate and multivariate analysis preoperative, tonic activation and perioperative HRV change were not significantly related to new POAF. However, in the postoperative phase, a marked increase or decrease of Δ Lg (LF/HF), Δ Lg (HF) and Δ Lg (LF) were associated with increased POAF risk. Further, examination of 10-minute epochs in the 30 minutes before the onset of POAF, revealed that progressive increase of HRV indexes. Conclusions POAF susceptibility is associated with postoperative dynamic HRV changes but not tonic autonomic state. Potentially the observation that POAF was preceded by progressive rise of HRV indexes may offer a promising signal for early warning of POAF, and permit preventive intervention.