Effect of diurnal variability of heart rate on development of arrhythmia in patients with chronic obstructive pulmonary disease.

We examined the possible effect of diurnal variability of heart rate on the development of arrhythmias in patients with chronic obstructive pulmonary disease (COPD). Forty-one COPD patients (M/F: 39/2, mean age: 59+/-8.5 years) and 32 (M/F: 27/5, mean age: 57+/-11 years) healthy controls were included. Twenty-four hour ECG recordings were analyzed for atrial fibrillation (AF) or ventricular premature beats (VPB), and circadian changes in heart rate variability (HRV) were assessed by dividing the 24-h period into day-time (08:00-24:00 h) and night-time (24:00-08:00 h) periods. Night-time total (TP), low frequency (LF) and high frequency (HF) powers were similarly lower from day-time parameters in AF(-) COPD patients (HF 3.91+/-1 vs. 4.43+/-1.04 ms(2), P=0.001) and controls (HF 3.95+/-0.72 vs. 4.82+/-0.66 ms(2), P<0.001). The LF/HF ratios were also significantly reduced in the same patient groups (AF(-) COPD 1.35+/-0.21 vs. 1.27+/-0.19, P=0.04, controls 1.43+/-0.14 vs. 1.24+/-0.09, P<0.001). Night-time TP and LF were increased, HF unchanged and LF/HF significantly increased (1.11+/-0.25 vs. 1.19+/-0.27, P<0.05) in AF(+) COPD patients. Frequency of VPB was correlated with corrected QT dispersion (QTc(d)) (r=0.52, P=0.001) and the day-time/night-time HF ratio (r=0.43, P=0.02). Patients with QTc(d)>or=60 ms did not have the expected increase in night-time HF and had a statistically insignificant increase in LF/HF ratio. In COPD patients with QTc(d)<60 ms, circadian changes in HRV parameters were parallel with the controls. We concluded that COPD patients with arrhythmia had circadian HRV disturbances such as unchanged night-time parasympathetic tone and disturbed sympatho-vagal balance in favor of the sympathetic system all day long, which may explain the increased frequency of arrhythmia.