The impact of posture on the cardiac depolarization and repolarization phases of the QT interval in healthy subjects

Abstract

BackgroundPostural changes affect both heart rate and the QT interval. ObjectiveTo investigate the effects of postural changes on the depolarization and repolarization phases of the QT interval. MethodsA three lead ECG from 12 healthy young volunteers was recorded in the standing, sitting and in the supine positions. For the purpose of this study, we defined the depolarization phase as the QRS complex plus the ST segment and the repolarization phase as the duration of the T wave. ResultsQTc did not change with changes in position. The ratio of the duration of the depolarization phase to the repolarization phase was higher in the supine position (0.98±0.13) compared to the standing position (0.83±0.17). ConclusionsThe origin of the T wave moves closer to the QRS complex during standing compared to the supine position. The observed changes are mainly due to shortening of the ST segment during standing compared to supine position.