Exercise-induced ischemia in patients with ischemic heart disease significantly increased the percentage change in QT dispersion compared to controls (52% vs 28%, p<0.002).
Observational (n=45)
Does exercise-induced ischemia increase QT interval dispersion in patients with ischemic heart disease, and do beta-blockers blunt this effect?
Exercise-induced ischemia significantly increases QT dispersion in patients with ischemic heart disease, an arrhythmogenic effect that appears to be blunted by beta-blocker therapy.
Absolute Event Rate: 52% vs 28%
p-value: p=<0.002
An increased spatial dispersion of ventricular repolarization duration (QT dispersion) is associated with an increased vulnerability to arrhythmias. This study was designed to examine the effect of exercise on QT dispersion in ischemic heart disease (IHD). QT dispersion, corrected QT dispersion, and percentage change in uncorrected and corrected QT dispersion between rest and peak exercise were examined in 14 members of a control group, 17 patients with IHD, and 14 patients with IHD who were receiving beta-blockers (IHD-B). All subjects had undergone a standard Bruce protocol exercise test, and QT intervals were measured at rest and peak exercise with a digitizing tablet interfaced to a personal computer. QT dispersion at rest was markedly increased in the IHD group compared with that in the control and IHD-B groups, respectively (corrected QT dispersion in milliseconds), 74 +/- 7, 40 +/- 4, 49 +/- 5, p < 0.03). The corrected QT dispersion at peak exercise was greater in the IHD group compared with that in the control group (57 +/- 5 vs 26 +/- 3 msec, p < 0.03). The percentage change in QT dispersion with exercise was significantly higher in the IHD group (52% +/- 5%) compared with that in both the control group (28% +/- 4%, p < 0.002) and the IHD-B group (30% +/- 3%, p < 0.01). A larger mean QT dispersion at peak exercise and an increased percentage change in QT dispersion with exercise may help explain the increased susceptibility of the IHD group for arrhythmias. The cardioprotective action of beta-blockers may be explained by their blunting effect on exercise-related changes in QT dispersion.
Roukema et al. (Thu,) conducted a observational in Ischemic heart disease (n=45). Exercise-induced ischemia vs. Control group was evaluated on Percentage change in QT dispersion with exercise (p=<0.002). Exercise-induced ischemia in patients with ischemic heart disease significantly increased the percentage change in QT dispersion compared to controls (52% vs 28%, p<0.002).