Noxious Arousal Induces T Wave Abnormalities in Healthy Subjects

Abstract

Background Sudden arousal has been associated with sudden cardiac death in individuals with ischaemic heart disease, cardiac arrhythmias and the congenital long QT syndrome. This study aimed to determine the effects of arousal on ventricular repolarisation in normal individuals by examining the dynamic QT-interval-heart rate relationship and T-wave morphology changes under various ‘arousal’ scenarios. Methods 18 healthy subjects (6 female, 12 male, median age 22) underwent four separate 24-hour ECG recordings using 2-channel Holter recorders. The protocol contained five different arousal events: Natural Waking (woke naturally, then stood up); Morning Alarm (woken by alarm in the morning, then stood up); Night Alarm (woken by alarm during the night, then stood up); Morning Alarm-Remain Lying (woken by alarm in the morning but remained supine) and Lying to Standing (stood up from a supine position during the day). Holter recordings were analysed using a commercial package for dynamic assessment of the QT-RR relationship. Results In the twenty minutes after arousal no changes were seen in overall QT-RR relationship in any of the groups. However, marked T-wave morphology changes, including T wave inversion, were observed in all the arousal events. Postural changes only accounted for a small proportion of change in T wave morphology. Conclusions In healthy subjects noxious arousal causes marked changes in the morphology of the T wave. This may reflect abnormal adaptation of repolarisation to sudden changes in heart rate and autonomic tone.