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The Turkish Journal of Pediatrics 2010; 52: 173-178 Original Heart rate variability in children with congenital sensorineural deafness Tayfun Uçar1, Ercan Tutar1, Mustafa Tekin2, Semra Atalay1 Divisions of 1Pediatric Cardiology, and 2Genetics, Ankara University Faculty of Medicine, Ankara, Turkey SUMMARY: Uçar T, Tutar E, Tekin M, Atalay S. Heart rate variability in children with congenital sensorineural deafness. Turk J Pediatr 2010; 52: 173-178. We hypothesized that decreased sympathetic/parasympathetic balance as a result of the absence of auditory stimuli on the autonomic nervous system might be an explanation for our previous finding of lower mean heart rate in congenitally deaf children. To test our hypothesis, we obtained heart rate variability (HRV) data of 23 children with congenital sensorineural deafness from 24-hour Holter ECG recordings and compared them to data of 18 healthy children. HRV was measured by calculating time-domain and frequency-domain indexes from 24-hour recordings and from 6 hours of recordings obtained while subjects were sleeping. We additionally compared the HRV values obtained from children with and without GJB2 gene mutations. We did not find any significant difference in HRV parameters between deaf children and healthy children. There were also no significant differences in HRV parameters between deaf children with and without GJB2 mutations. We conclude that cardiac autonomic dysfunction does not seem to be present in patients with congenital sensorineural deafness. Key words: sensorineural deafness, heart rate variability, autonomic nervous system. Heart rate variability (HRV) represents a types of gap junction genes, GJB2 and GJB3 noninvasive parameter for studying cardiac genes, encoding connexin 26 and connexin 31 autonomic control1,2. Decreased HRV is a sign proteins, respectively, are commonly detected of autonomic imbalance and is an independent in different populations17. predictor of increased morbidity and mortality In our previous study, which was conducted in with various forms of heart disease and sudden order to investigate repolarization abnormalities, death. Decreased variability was found in adult consisting of approximately 800 children, patients with myocardial infarction3,4, chronic we surprisingly found that congenitally deaf heart failure5,6, left ventricular dysfunction5, children had lower mean heart rate than their low cardiac output7, and diabetic neuropathy8. healthy counterparts 18 . We proposed that In the pediatric age group, HRV has been decreased sympathetic tone as a result of the investigated in diabetes mellitus9, respiratory absence of auditory stimuli on the autonomic distress syndrome of the newborn10,11, sudden nervous system in deaf children might be infant death syndrome 12, congenital heart an explanation. To test that hypothesis, we disease both before and after operation 13, obtained HRV data from 24-hour Holter critically ill children following cardiac surgery14, ECG recordings in a group of children with and normal infants and children 2,15,16, but congenital sensorineural deafness and compared has not yet been extensively investigated data to those of healthy school children. To in children with congenital sensorineural exclude the effect of acoustic stimuli on the deafness. The most common cause of congenital autonomic nervous system, we also compared hearing impairment has been shown to be the HRV data obtained during the daytime with impairment of the function of different gap that during sleep. In order to evaluate the effect junction proteins 17. Mutations in the beta of mutations in the GJB2 and GJB3 genes, we 174 Uçar T, et al
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