The impact of posture on the cardiac depolarization and repolarization phases of the QT interval in healthy subjects.
Postural changes affect both heart rate and the QT interval.



To investigate the effects of postural changes on the depolarization and repolarization phases of the QT interval.



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.



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).



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.
Division of Cardiac Anesthesia, Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Yurie
Y
Obata
Sobolev Institute of Mathematics, Novosibirsk, Russia; Novosibirsk State University, Novosibirsk, Russia.
Pavel
P
Ruzankin
Newcastle University School of Medicine, Newcastle, UK.
Qi Jia
QJ
Ong
Division of Cardiac Anesthesia, Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Dan E
DE
Berkowitz
Departments of Medicine and Biomedical Engineering, Johns Hopkins University, Baltimore, MD, USA.
Ronald D
RD
Berger
Division of Cardiac Anesthesia, Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Jochen
J
Steppan
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.
Viachaslau
V
Barodka
D000328:Adult; D004562:Electrocardiography; D005260:Female; D064368:Healthy Volunteers; D006329:Heart Conduction System / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011187:Posture / Q000502:physiology*
Depolarization; Electrocardiogram; QT interval; Repolarization; T wave