Yurie Obata1, Pavel Ruzankin2, Qi Jia Ong3, Dan E Berkowitz1, Ronald D Berger4, Jochen Steppan1, Viachaslau Barodka5. 1. Division of Cardiac Anesthesia, Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD, USA. 2. Sobolev Institute of Mathematics, Novosibirsk, Russia; Novosibirsk State University, Novosibirsk, Russia. 3. Newcastle University School of Medicine, Newcastle, UK. 4. Departments of Medicine and Biomedical Engineering, Johns Hopkins University, Baltimore, MD, USA. 5. Division of Cardiac Anesthesia, Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD, USA. Electronic address: vbarodk1@jhmi.edu.
Abstract
BACKGROUND: Postural changes affect both heart rate and the QT interval. OBJECTIVE: To investigate the effects of postural changes on the depolarization and repolarization phases of the QT interval. METHODS: A 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. RESULTS: QTc 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). CONCLUSIONS: The 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.
BACKGROUND: Postural changes affect both heart rate and the QT interval. OBJECTIVE: To investigate the effects of postural changes on the depolarization and repolarization phases of the QT interval. METHODS: A 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. RESULTS:QTc 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). CONCLUSIONS: The 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.