Cardiology in the Young (2011), 21, 130–135 doi:10.1017/S1047951110001514 r Cambridge University Press, 2010 Original Article QT dispersion in childhood obstructive sleep apnoea syndrome Anant Khositseth, Palinee Nantarakchaikul, Teeradej Kuptanon, Aroonwan Preutthipan Faculty of Medicine, Department of Pediatrics, Ramathibodi Hospital, Mahidol University, Bangkok, Thailand Abstract The difference between maximal and minimal QT interval and corrected QT interval defined as QT dispersion and corrected QT dispersion may represent arrhythmogenic risks. This study sought to evaluate QT dispersion and corrected QT dispersion in childhood obstructive sleep apnoea syndrome. Forty-four children (34 male) with obstructive sleep apnoea syndrome, aged 6.2 plus or minus 3.5 years along with 38 healthy children (25 male), 6.6 plus or minus 2.1 years underwent electrocardiography to measure QT and RR intervals. Means QT dispersion and corrected QT dispersion were significantly higher in obstructive sleep apnoea syndrome than controls, 52 plus or minus 27 compared to 40 plus or minus 14 milliseconds (p equal to 0.014), and 71 plus or minus 29 compared to 57 plus or minus 19 milliseconds (p equal to 0.010), respectively. Interestingly, QT dispersion and corrected QT dispersion in obstructive sleep apnoea syndrome with obesity, 57 plus or minus 30 and 73 plus or minus 31 milliseconds, were significantly higher than in control, 40 plus or minus 14 and 57 plus or minus 19 milliseconds (p equal to 0.009 and 0.043, respectively). However, QT dispersion and corrected QT dispersion in obstructive sleep apnoea syndrome without obesity, 43 plus or minus 20 and 68 plus or minus 26 milliseconds, were not significantly different. In conclusion, QT dispersion and corrected QT dispersion were significantly increased only in childhood obstructive sleep apnoea syndrome with obesity. Obesity may be the factor affecting the increased QT dispersion and corrected QT dispersion. Keywords: Electrocardiography; children; arrhythmia Received: 15 February 2010; Accepted: 20 September 2010; First published online: 12 November 2010 O BSTRUCTIVE SLEEP APNOEA SYNDROME IS DEFINED as a disorder of breathing during sleep characterised by repeated episodes of inter- mittent partial or complete upper airway obstruc- tion during sleep that results in disruption of normal ventilation and sleep patterns. 1 Obstructive sleep apnoea syndrome in the paediatric population is now increasing with an increase in obstructive sleep apnoea syndrome from 0.1% to 13%, but mostly between 1% and 4%. 2,3 Accumulating data suggested that obstructive sleep apnoea syndrome is more common among overweight or obese boys with peak ages between 2 and 8 years. 2 Childhood obstructive sleep apnoea syndrome is associated with multi-organ morbidities, including cardio- vascular complications, poor growth, and neuro- behavioral problem. Cardiovascular complications may develop in children with obstructive sleep apnoea syndrome and have an immediate significant impact on cardiovascular health during childhood. Moreover, some of the effects on the cardiovascular system may also affect cardiovascular outcomes later during adulthood. The cardiopulmonary complica- tions including cardiac failure, arrhythmia, sys- temic, and pulmonary hypertension are the most serious complications. 4 The QT interval in different leads can vary and the difference between the maximal and minimal QT intervals defined as QT dispersion may reflect inhomogeneity of repolarisation and myocardial electrical instability. 5 Due to the effect of heart rate on ventricular recovery time, the difference between the maximal and minimal corrected QT intervals Correspondence to: Dr A. Khositseth, Faculty of Medicine, Department of Pediatrics, Ramathibodi Hospital, 270 Rama VI, Ratchathevee, Bangkok 10400, Thailand. Tel: 662 201 1685; Fax: 662 201 1850; E-mail: alaks@diamond.mahidol.ac.th