Sleep Arousal and Sudden Changes in Cardiac QT Interval

Sleep arousal is generally defined as an abrupt shift in EEG frequency with a duration of 3-16 seconds. Arousal from sleep expected to cause sudden changes in the cardiovascular system that can manifest as cardiac responses. In this paper, our objective was to investigate how cardiac characteristics change due to arousal. We focused on the QT interval fluctuations in ECG during the occurrence of arousals. We analysed 7373 sleep arousals collected from 50 males that were older than 65 years. We analysed the ECG signal 5 seconds prior to and 10 seconds after each arousal onset (Pre and Post-Onset). Q and T waves were detected for all Pre and Post-Onset windows to estimate their time intervals. To find out whether the QT interval, a marker of ventricular activation, is modulated by arousal onset, we have applied graphical and statistical analysis. Our observations indicate that in 47 out of 50 subjects (94%), the average QT interval of all arousal significantly shortened at arousal onset. We observed similar outcomes for different types of arousals, indicating that the shortening in average QT interval is independent of the type of arousal. We also studied the relative QT interval change during arousal. The distribution of relative QT interval changes demonstrates that around 60% of arousals increase or decrease QT interval by a maximum of 20%. The probability of QT time interval shortening was twice that of QT interval lengthening.