Abstract P391: The Effects of Obstructive Sleep Apnea on Cardiac Arrhythmia Risk

Abstract

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. OSA events have previously been shown to cause prolonged QT intervals compared to the post-apnea hyperventilation period, and studies have also observed increased QT dispersion in patients without cardiac disease. However, those with cardiac disease may be at the greatest risk for SCD, and it is not known what role QT prolongation plays and what factors influence these responses. Thus, the purpose of this study is to evaluate 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 36 patients undergoing polysomnography for diagnosis of OSA. Patients that were selected had an apnea hypopnea index >20/Hr and had no prior myocardial infarction or heart failure. Each patient’s ECG during their sleep study was analyzed to assess QT interval throughout the night. Baseline QT intervals were compared to QT intervals during obstructive apneas during the first 2 hours of sleep (Early) and last 2 hours of sleep (Late). In addition, apneas >40 seconds were analyzed in 11 patients for changes in QTc as the apnea progressed. Statistical comparisons were made with paired t tests and a one-way ANOVA analysis with repeated measures. Results: Early analyses of data showed QTc intervals in Early and Late apneas were significantly prolonged compared to awake baseline (p=0.04 and p=0.006 respectively). For patients with apneas >40 seconds, significant differences in QTc interval were observed at increasing time points during the apnea compared to the QTc immediately preceding the apnea (p<0.001). Furthermore, patients with longer apneas tend to have longer baseline QTc (p=0.07). 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. Furthermore, prolongation tends to increase as the apnea duration progresses. Early data analyses also suggest that baseline QTc tends to be longer in patients who have more severe/longer apneic events throughout the night. 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.