| Abstract: |
Background: Postoperative atrial fibrillation/flutter (AF) is associated with significant morbidity but its mechanisms are poorly understood. Methods: During a 6 yr study of post-thoracotomy patients with Holter recordings, 48 patients (M/F 32/16) aged 70+-8 yr after lobectomy (n=37) or pneumonectomy (n=11) who developed sustained AF within 96 h after surgery, had HRV analysis performed in the 2 h preceding the onset of AF. HRV (5 min) indices were mean RR (ms); standard deviation of RRs (SD, ms), root-mean square of difference of successive RRs (rMSSD, ms), proportion of adjacent RRs > 50 ms different (pNN50, %), low frequency (LF; 0.04 - 0.15 Hz); high frequency (HF; 0.15 - 0.4 Hz) power and LF/LF+HF (%, sympathetic index). Data (mean +- SD) were analyzed with ANOVA. Results: RR decreased modestly prior to AF onset (P=0.02) and %LF index did not change. All other parameters of HRV increased significantly over the 2 h before AF (Table). Conclusions: Prior to AF onset there was a significant increase in time and frequency domain parameters of HRV during a period of relative tachycardia. To the best of our knowledge, these findings are novel and consistent with parasympathetic resurgence as the triggering mechanism for postoperative AF in patients presumed to have adrenergic hyperactivity. |
