CHANGES IN THE QT INTERVAL DURING OBSTRUCTIVE SLEEP-APNEA

Abnormalities of ventricular repolarization are associated with life-threatening ventricular arrhythmias. The effects of obstructive sleep apnea on the QT interval were evaluated in 12 male patients with obstructive sleep apnea syndrome (OSAS) who had no evidence of underlying cardiac, pulmonary or central nervous system disease. Seventy episodes of OSAS during nonrapid eye movement (NREM) sleep were randomly selected for analysis of RR and QT intervals. Differences in the QT interval, corrected QT interval (QTc) and RR interval just before the onset of apnea, at the end of apnea and during the postapnea hyperventilation period were compared. As expected, the RR interval prolonged considerably during OSAS (1,499 +/- 128 msec) compared to quiet sleep (1,019 +/- 131 msec, p < 0.002) and decreased during the postapnea hyperventilation period (969 +/- 152 msec, p < 0.002). The QT interval was prolonged at the onset of apnea (482 +/- 34 msec) compared to the active awake state (421 +/- 10 msec, p < 0.01). Further prolongation of the QT interval was observed during OSAS (528 +/- 64 msec, p < 0.002). The QT interval shortened abruptly during the postapnea hyperventilation period (435 +/- 34 msec, p < 0.002). The QTc was also prolonged during the onset of apnea (482 +/- 34 msec) and shortened significantly during apnea (435 +/- 34 msec, p < 0.002) and during the postapnea hyperventilation period (423 +/- 39 msec). Significant variations of the RR interval, QT and QTc intervals were not observed during episodes of NREM sleep after initiation of effective therapy in six patients. Thus, significant prolongation of the QT interval is observed during severe OSAS and abrupt shortening of the QT interval occurs during the postapnea hyperventilation period. Whether these abnormalities of ventricular repolarization are associated with the development of ventricular arrhythmias in this patient population remains unknown.