Comparison of heart rate variability in patients with chronic fatigue syndrome and controls.

Recent studies have reported a close association between chronic fatigue syndrome and neurally mediated hypotension. We hypothesized that this association may result from an abnormality in autonomic function among patients with chronic fatigue syndrome, which may be detectable using an analysis of heart rate variability. We prospectively studied 19 patients who fulfilled the Centers for Disease Control criteria for chronic fatigue syndrome and 11 controls. Each subject underwent a two-stage tilt-table test while wearing a Holter monitor. Heart rate variability was assessed in the supine baseline position and during upright tilt using frequency domain parameters. In the baseline supine position, high frequency (HF) power, low frequency (LF) power, and the ratio of low frequency power to high frequency power (LF/HF ratio) were similar. In both patient groups, upright tilt resulted in a similar decrease in HF power, increase in LF power, and increase in the LH/HF ratio. In conclusion, autonomic function, as assessed using an analysis of heart rate variability, does not differ in the baseline supine state, nor in response to upright tilt among patients with chronic fatigue syndrome and healthy controls.