title: Effect of CPAP on QT interval dispersion in obstructive sleep apnea patients without hypertension.
abstract: OBJECTIVE
  Delayed cardiac repolarization leading to prolongation of the QT interval is a well-characterised precursor of arrhythmias. Obstructive sleep apnea (OSA) might cause arrhythmias, since QT corrected interval dispersion (QTcd) is increased in these patients. We aimed to determine the effect of nasal continuous positive airway pressure (CPAP) therapy on QTcd in OSA patients without hypertension.
  
  
  METHODS
  An overnight polysomnography (PSG) and a standard 12-lead electrocardiogram (ECG) were performed on 49 subjects without hypertension, diabetes mellitus, cardiac or pulmonary disease or any hormonal, hepatic, renal or electrolyte disorders. In 29 moderate-severe OSA (apnea-hypopnea index: AHI15) patients, QTd (defined as the difference between the maximum and minimum QT interval) and QTcd were calculated using the Bazzet formula at baseline and after six months of CPAP therapy.
  
  
  RESULTS
  Eighteen patients were compliant with nasal CPAP, and mean age was 46.5+/-4.9 years. Patients had high body mass index (BMI: 30.6+/-4.0 kg/m(2)), but there was no change in either BMI or blood pressure after six months. A strong positive correlation was shown between QTcd and AHI (p<0.001, r=0.913). The QTcd at baseline (54.5+/-8.7 ms) significantly decreased after CPAP therapy (35.5+/-4.2 ms, p<0.001), although it did not significantly change in 11 non-compliant patients.
  
  
  CONCLUSIONS
  In OSA patients without hypertension, CPAP therapy improves the inhomogeneity of repolarization via a significant decrease in QTcd.
authors.affiliation: Pamukkale University Medical Faculty, Department of Cardiology, 20200 Kinikli, Denizli, Turkey. dursundursunoglu@yahoo.com
authors.forename: Dursun
authors.initials: D
authors.lastname: Dursunoglu
authors.forename: Nese
authors.initials: N
authors.lastname: Dursunoglu
mesh_terms: D000328:Adult; D015992:Body Mass Index; D045422:Continuous Positive Airway Pressure / Q000379:methods*; D005260:Female; D006801:Humans; D006973:Hypertension / Q000150:complications / Q000175:diagnosis; D008133:Long QT Syndrome / Q000209:etiology / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D017286:Polysomnography / Q000379:methods*; D012720:Severity of Illness Index; D020181:Sleep Apnea, Obstructive / Q000150:complications / Q000628:therapy*; D016896:Treatment Outcome