DELAYED IMPROVEMENT OF AUTONOMIC NERVOUS ABNORMALITY AFTER THE MAZE PROCEDURE - TIME AND FREQUENCY-DOMAIN ANALYSIS OF HEART-RATE-VARIABILITY USING 24-HOUR HOLTER MONITORING

Objective-To analyse heart rate variability in patients with atrial fi brillation after the Maze procedure, to investigate whether the proced ure damages the cardiac autonomic fibres supplying the sinus node. Des ign 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 proced ure (Maze group) and in seven patients who underwent cardiac surgery w ithout the Maze procedure (control group). Mean RR intervals (mRR) and the standard deviation of successive RR intervals (SDRR) were determi ned by time domain analysis, and high frequency (HF), low frequency (L F), and total power (TP) spectral components of RR variability were ca lculated by frequency domain analysis. Holter monitoring was also perf ormed at six and 12 months after cardiac surgery in the Maze group. Re sults-Circadian variation (mean (SD)) in mRR (daytime to night time di fference: 119 (60) v 302 (143) ms), SDRR (daytime: 8.4(3.3) v 37.0 (12 .0) ms), TP (daytime: 46.7(16.0) v 171.8(30.4)ms), HF (daytime: 19.6(9 .9) v 36.7(7.1)ms(2)), and LF/HF (daytime: 0.31(0.07) v 1.18 (0.46)) w as 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 < 0.0 5). Conclusions-Surgery combined with the Maze procedure markedly supp ressed the circadian variation of heart rate over a 24 hour period wit hin one month after surgery, mainly because of damage to the innervati on of the sinus node. However, at six and 12 months there was restorat ion of circadian variation, probably as the result of reinnervation of the sinus node.