title: Body position effects on the ECG: implication for ischemia monitoring.
abstract: Rotation of the heart in relation to surface electrocardiographic (ECG) electrodes when a patient turns to one side has been reported to cause ST-segment shifts, triggering false alarms with continuous ST-segment monitoring. We prospectively analyzed ST-segment and QRS complex changes in both standard and derived ECGs in 40 subjects (18 with heart disease and 22 healthy) in supine, right- and left-lying positions. Of the 40 subjects, 6 (4 cardiac, 2 healthy) developed positional ST deviations of 1 mm or more on the standard ECG. In the derived method, five of the same six subjects showed ST-segment deviation of which most occurred in the left-lying position. Positional ST changes were most frequent for males and for cardiac patients (33%). Changes in QRS complex morphology were common on the standard (28 of 40, 70%) and less frequent on the derived ECGs (17 of 40, 43%), occurring in both healthy and cardiac subjects. QRS axis changes occurred only on the standard ECG. It was concluded that (1) right and left side-lying positions frequently induce clinically significant ECG changes; (2) positional ST-segment deviation is less frequent than previously reported and is most likely to occur in males with cardiac disease; and (3) the derived method is less prone to positional QRS changes than the standard ECG.
authors.affiliation: Department of Physiological Nursing, University of California, San Francisco, 94143, USA.
authors.forename: M G
authors.initials: MG
authors.lastname: Adams
authors.forename: B J
authors.initials: BJ
authors.lastname: Drew
mesh_terms: D000328:Adult; D000368:Aged; D006332:Cardiomegaly / Q000175:diagnosis; D004562:Electrocardiography; D005260:Female; D006801:Humans; D008297:Male; D017202:Myocardial Ischemia / Q000175:diagnosis; D011187:Posture / Q000502:physiology*