Increased ventricular repolarization inhomogeneity during postural changes in patients with syndrome X
Journal
American Journal of Cardiology
Journal Volume
82
Journal Issue
5
Pages
615-620
Date Issued
1998
Author(s)
Abstract
The interlead variation in QT interval (QT dispersion) can be used to assess regional inhomogeneity of ventricular repolarization under a variety of conditions, including stress. Patients with syndrome X may have increased sympathetic activity that could change QT interval regionally and give rise to an increase in QT dispersion under exercise testing. To test the hypothesis, 26 consecutive patients with syndrome X (group 1) were studied. Two additional groups matched in terms of age, sex, and left ventricular mass index consisting of 26 nonconsecutive patients with coronary artery disease (group 2) and 20 normal subjects (group 3) were studied for comparison. Standing induced a significantly higher increase of heart rate in group 1 than in groups 2 and 3 (7.5 ± 6.0 vs 4.0 ± 6.3 and 1.1 ± 3.6 beats/min; p = 0.05 and 0.003, respectively). There were significant differences in QT dispersion between groups 1 and 2 on upright standing (48 ± 12 vs 34 ± 14 ms, p = 0.0003), but not at baseline (33 ± 14 vs 38 ± 11 ms, p = NS) or at peak exercise (38 ± 9 vs 38 ± 9 ms, p = NS). Results did not change when QT(c) dispersion was substituted for QT dispersion. From a conditional multivariate logistic regression analysis, the only independent predictor of occurrence of syndrome X on upright standing was QT(c) dispersion (odds ratio = 1.255, p = 0.01). Electrocardiographic QT(c) dispersion provides important clinical information. Patients with syndrome X had a higher increase of heart rate and QT(c) dispersion in response to standing from the supine position compared with patients with coronary artery disease and normal subjects.
SDGs
Other Subjects
adult; aged; article; body posture; clinical article; controlled study; coronary artery disease; female; heart left ventricle mass; heart repolarization; human; male; priority journal; qt interval; sympathetic tone; syndrome X; tachycardia; Adult; Aged; Cardiac Volume; Coronary Arteriosclerosis; Electrocardiography; Exercise Test; Female; Heart Rate; Heart Ventricles; Humans; Long QT Syndrome; Male; Microvascular Angina; Middle Aged; Posture; Sensitivity and Specificity; Sympathetic Nervous System
Type
journal article