Heart Rate Variability in Congenital Central Hypoventilation Syndrome
ABSTRACT: Heart rate variability was assessed in 12 patients with congenital central hypoventilation syndrome (CCHS) and in age- and sex-matched controls using SD of time intervals between R waves (R-R intervals), R-R interval histograms, spectral analysis, and Poincaré plots of sequential R-R intervals over a 24-h period using ambulatory monitoring. Mean heart rates in patients with CCHS were 103.3 ± 17.7 SD and in controls were 98.8 ± 21.6 SD (p > 0.5, NS). SD analysis of R-R intervals showed similar results in both groups (CCHS 102.2 ± 36.0 ms versus controls 126.1 ± 43.3 ms; p > 0.1, NS). Spectral analysis revealed that, for similar epochs sampled during quiet sleep and wakefulness, the ratios of low-frequency band to high-frequency band spectral power were increased for 11 of 12 patients with CCHS during sleep, whereas a decrease in these ratios was consistently observed in all controls during comparable sleep states (χ2 = 20.31; p < 0.000007). During wakefulness, the ratios of low-frequency band to high-frequency band spectral power were similar in both patients with CCHS and controls. Poincaré plots displayed significantly reduced beat-to-beat changes at slower heart rates in the CCHS patients (χ2 = 24.0; p < 0.000001). The scatter of points in CCHS Poincare plots was easily distinguished from controls. AH CCHS patients showed disturbed variability with one or more measures. The changes in moment-to-moment heart rate variability suggest that, in addition to a loss of ventilatory control, CCHS patients exhibit a dysfunction in autonomic nervous system control of the heart.