Objective To analyse heart rate variability in patients with atrial fibrillation after the Maze procedure, to investigate whether the procedure damages the cardiac autonomic fibres supplying the sinus node.

Design and patients Time and frequency domain analyses of RR variability were performed using 24 hour Holter monitoring one month after surgery in 12 patients with atrial fibrillation who underwent the Maze procedure (Maze group) and in seven patients who underwent cardiac surgery without the Maze procedure (control group). Mean RR intervals (mRR) and the standard deviation of successive RR intervals (SDRR) were determined by time domain analysis, and high frequency (HF), low frequency (LF), and total power (TP) spectral components of RR variability were calculated by frequency domain analysis. Holter monitoring was also performed at six and 12 months after cardiac surgery in the Maze group.

Results Circadian variation (mean (SD)) in mRR (daytime to night time difference: 119 (60) v302 (143) ms), SDRR (daytime: 8.4 (3.3) v37.0 (12.0) ms), TP (daytime: 46.7 (16.0) v171.8 (30.4) ms), HF (daytime: 19.6 (9.9) v36.7 (7.1) ms²), and LF/HF (daytime: 0.31 (0.07)v 1.18 (0.46)) was decreased in the Maze group at one month compared with the control group (p < 0.01), but showed improvement at six and 12 months (p < 0.05).

Conclusions Surgery combined with the Maze procedure markedly suppressed the circadian variation of heart rate over a 24 hour period within one month after surgery, mainly because of damage to the innervation of the sinus node. However, at six and 12 months there was restoration of circadian variation, probably as the result of reinnervation of the sinus node.