Autonomic nervous system function in severe breath-holding spells.

This study attempted to determine noninvasively whether a dysregulation of autonomic nervous system reflexes exists in children with severe cyanotic breath-holding spells (BHS). This was a cross-sectional study performed in the neurophysiology laboratory at a tertiary care hospital. Patients, 18 months of age and older taken from a referral population of children with severe cyanotic BHS and normal controls, were studied. Fourteen children with cyanotic BHS and 12 controls were evaluated. Several noninvasive measures of parasympathetic and sympathetic reflex functions were assessed and statistically analyzed using analysis of variance and covariance, and Fisher's exact tests. The cyanotic BHS group had a significantly greater increase in pulse rate at 15 s of standing after rising from the supine position (P < .06), with a trend toward a concomitant higher mean arterial pressure (P < .09). After adjusting for age, sex, and mean supine systolic and diastolic blood pressures, breath-holders had a greater decrease in diastolic blood pressure (P < .02) without an increase in systolic blood pressure after standing from the supine position. Breath-holders also had significantly abnormal 30:15 R-R interval ratios compared with controls (P < .002). These results support the hypothesis that children with cyanotic BHS have underlying autonomic nervous system dysregulation. This dysregulation may contribute to the pathophysiology of severe BHS in these children.