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Acute ischaemia: a dynamic influence on QT dispersion
S C Sporton1, P Taggart, P M Sutton
1Department of Academic, University College London Medical School, UK.
Insights
Acute myocardial ischemia significantly increases QT dispersion in patients with coronary artery disease. This inducible QT dispersion may help assess arrhythmia risk better than resting measurements.
Area of Science:
- Cardiology
- Electrophysiology
Background:
- QT dispersion (QTd) is a measure of repolarization variability.
- Assessing myocardial ischemia's impact on QTd is crucial for understanding arrhythmia risk.
Purpose of the Study:
- To test if acute myocardial ischemia increases QT dispersion.
- To evaluate the utility of inducible QT dispersion in coronary artery disease (CAD).
Main Methods:
- 18 patients with CAD underwent incremental atrial pacing to induce ischemia.
- QT dispersion was measured using a 12-lead electrocardiogram.
- 6 patients with normal coronary arteries served as controls.
Main Results:
- Patients with CAD showed significant increases in QT dispersion (mean 38 ms) during ischemia.
- Control patients without ischemia had no significant change in QT dispersion.
- Baseline QT dispersion did not differentiate between CAD patients and controls.
Conclusions:
- Myocardial ischemia acutely increases QT dispersion in CAD patients.
- Inducible QT dispersion may be a superior predictor of arrhythmic events compared to resting QT dispersion.
Background:
The aim of this study was to test the hypothesis that acute myocardial ischaemia increases QT dispersion measured from the 12-lead electrocardiogram.
Methods:
Incremental atrial pacing was used to induce myocardial ischaemia in 18 patients with coronary artery disease and QT dispersion was measured. Six patients with normal coronary arteries served as the control group.
Findings:
All the patients with coronary artery disease developed angina and/or ST depression accompanied by marked increases in QT dispersion (mean increase 38 ms, 95% CI 30 to 45 ms, p < 0.001). In contrast, in the six patients with normal coronary arteries who remained without symptoms and without ST changes, there was no significant change in QT dispersion in response to pacing. Baseline QT dispersion did not distinguish those patients with coronary artery disease from those with normal coronary arteries (44 ms [95% Cl 39-49 ms] vs 40 ms [25-55 ms]), respectively.
Interpretation:
These results demonstrate that myocardial ischaemia induced by incremental atrial pacing in patients with coronary artery disease causes an acute increase in QT dispersion. Such "inducible" QT dispersion may prove more useful than resting QT dispersion in assessing the individual risk of arrhythmic events in patients with coronary artery disease.