A PRELIMINARY STUDY ON THE SYMPATHOVAGAL BALANCE OF PEDIATRIC PATIENTS WITH CYCLIC VOMITING SYNDROME

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Background: Cyclic Vomiting Syndrome (CVS) is characterized by “fits of vomiting [active state], which recur after intervals of uncertain length” (Forbes, 1995). No signs of disease occur between these episodes, labelled the “passive state” in this study. Treatment of CVS is variably successful as most CVS children are refractory to antiemetics. The development of effective treatment is hampered by poor understanding of the cause(s) of CVS. Other disorders produce a pattern of cyclic vomiting which makes the diagnosis of CVS difficult.

Purpose: To determine whether there is a difference in sympathovagal balance when comparing the active state to the passive state in children with CVS.

Methods: The heart rate variability of 24 hr ECG recordings were analyzed by power spectral analysis to determine sympathovagal balance for both active and passive state in each patient.

Results: Three of five patients studied demonstrated a significant increase in sympathetic activity (p<0.05) during the active recording period. All three of these patients also exhibited excess vomiting (>20) during the 24 hours analyzed. The remaining two patients who vomited less than 10 times per day did not show a significant difference between active and passive recordings.

Conclusion: The preliminary study suggested that a difference in sympathovagal balance between the active state and passive state. Further study needs to be done to determine if the difference in sympathovagal balance is due to increased sympathetic outflow or insufficient modulation by the parasympathetic nervous system. Qualitative measurement of sympathovagal balance may provide a new diagnostic tool or provide insight into the etiology of the disorder.