The Effects of Obstructive Sleep Apnea on Cardiac Arrhythmia Risk

Background: Over 20 million people in the United States suffer from Obstructive Sleep Apnea (OSA). Compared to the general population, OSA patients are 2.6 times more likely to experience sudden cardiac death (SCD), and it is suspected that this is due in part to QT prolongation leading to fatal dysrhythmias. We examined the factors that affect QT interval during periods of sleep apnea including OSA severity, time of night, and quantity of obstructive apneic events during sleep. Methods: We determined QTc intervals from the electrocardiograms of 41 patients undergoing polysomnography for diagnosis of OSA. Patients that were selected had an apnea hypopnea index >20/Hr and had no prior heart disease. Each patient's ECG during their sleep study was analyzed to assess QT interval throughout the night. Results: Early analyses of data showed that QTc intervals in early and late apneas were significantly prolonged compared to baseline. Patients with longer apneas tended to have greater increases in QTc. Furthermore, there were no significant differences in the prolongation of QTc between males and females. Conclusions: Sleep apneic events are associated with periods of mild QTc prolongation despite some cardiac cycle shortening. The prolongation tends to become enhanced later in the night, implying that there is a cumulative effect of numerous prior apneas. Future studies will focus on QTc changes in OSA patients with prior heart disease, as these are the patients at greatest risk for serious arrhythmias during the night.