Daytime cardiac repolarization in patients with obstructive sleep apnea

Purpose: Obstructive sleep apnea (OSA) has been implicated in complications of cardiovascular disease, including arrhythmias and sudden cardiac death (SCD). Prolonged QT interval is associated with arrhythmias and SCD in patients with cardiovascular disease and apparently healthy humans. Apneic episodes during sleep in OSA patients are associated with QT prolongation due to increased vagal activity, but it is not understood whether chronic QT prolongation persists during normoxic daytime wakefulness. Methods: To determine whether daytime QT intervals in OSA patients are prolonged compared to control subjects, we recruited 97 (76 male, 21 female) newly diagnosed patients with OSA [apnea-hypopnea index (AHI) ≥5 events/h] and 168 (100 male, 68 female) healthy volunteers (AHI <5 events/h) and measured daytime resting QT and RR intervals from the electrocardiograms to determine QT prolongation corrected for heart rate (QTc). Results: All subjects with OSA were older and heavier, with increased heart rate, significantly increased AHI and arousal index, and reduced oxygen saturation (SpO₂) during sleep, and spent less time in sleep with >90 % SpO₂ compared to respective controls. QTc in patients with OSA (410 ± 3.3 for male and 433 ± 5.6 for female) was significantly increased compared to respective control groups (399 ± 2.9 for male and 417 ± 2.9 for female), after adjustment for age and body mass index. Conclusions: Our data show that OSA in either men or women is associated with a significant increase in resting daytime QTc. The propensity for ventricular arrhythmias in patients with OSA may be a result of abnormalities in resting cardiac repolarization.