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Changes of QT dispersion in patients with coronary artery disease dependent on different methods of stress induction
B Hailer1, P Van Leeuwen, D Sallner
1Department of Medicine, Philippusstift, Essen, Germany.
Insights
Stress-induced increases in QT dispersion (QTd) can identify coronary artery disease (CAD). Pharmacologic stress, particularly with arbutamine, showed greater differences in QTd compared to exercise, suggesting a lower ischemic threshold.
Area of Science:
- Cardiology
- Electrophysiology
- Diagnostic Imaging
Background:
- Stress-induced myocardial ischemia in coronary artery disease (CAD) patients can elevate QT dispersion (QTd).
- QTd is a measure of repolarization variability on an electrocardiogram (ECG).
Purpose of the Study:
- To investigate the impact of increasing heart rates on QTd.
- To compare different stress induction methods for estimating QTd in CAD patients with varying disease severity.
Main Methods:
- 58 patients underwent ECGs at rest, during dynamic exercise, and pharmacologic stress (arbutamine).
- QTd was calculated by subtracting the minimal from the maximal QT interval duration at each stress level.
- Echocardiography was used simultaneously with stress testing.
Main Results:
- QTd was significantly higher in CAD patients at maximal heart rate, with pharmacologic stress yielding better group discrimination (p < 0.0001 for arbutamine).
- Patients with prior myocardial infarction (MI) exhibited higher QTd values under all conditions.
- Pharmacologic stress induced more radical QTd changes in CAD patients compared to dynamic exercise.
Conclusions:
- QTd under stress effectively identifies patients with CAD.
- Pharmacologic stress, especially with arbutamine, is more sensitive than dynamic exercise in revealing QTd abnormalities.
- Elevated resting QTd in post-MI patients may mask stress-induced changes, indicating a potentially lower ischemic threshold.
Background:
Episodes of stress-induced myocardial ischemia in patients with coronary artery disease (CAD) may cause increases of QT dispersion (QTd).
Hypothesis:
Aim of this study was to analyze the effect of increasing heart rates on QTd and to compare the effect of different methods of stress induction in patients with varying degrees of CAD when estimating QTd.
Methods:
We studied 58 patients, 22 with prior myocardial infarction (MI), 25 without MI or wall motion disturbances at rest, and 11 patients without evidence of CAD. Prior to coronary angiography, standard 12-lead ECGs were obtained at rest as well as during dynamic exercise and pharmacologic stress using arbutamine simultaneously with echocardiography. QTd was determined at each stress level by subtracting minimal from maximal QT interval duration.
Results:
QTd values at rest were not consistently higher in the patients with CAD. At maximal heart rate, QTd was statistically significantly higher in patients with CAD with a better discrimination between groups for pharmacologic stress (p < 0.005 for exercise, p < 0.0001 for arbutamine). Patients after MI had higher QTd values under all conditions than did the groups without MI. As in patients with CAD, the values of this group changed more radically as a result of pharmacologic stress.
Conclusion:
Patients with CAD can be identified on the basis of QTd under stress. These changes were not as marked in patients with MI as their rest values were already increased. Overall, drug-induced stress produced greater differences than dynamic exercise, suggesting that the ischemic threshold might be lower in the former.