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Influence of coronary artery bypass grafting on QT dispersion
Iwona Woźniak-Skowerska1, Maria Trusz-Gluza, Mariusz Skowerski
11st Department of Cardiology, Silesian Medical University, Katowice, Poland.
Insights
Coronary artery bypass grafting (CABG) significantly reduces QT dispersion (QTd) both at rest and during exercise in patients with coronary heart disease. QT dispersion during exercise may help identify recurrent ischemia post-CABG.
Area of Science:
- Cardiology
- Electrophysiology
- Cardiac Surgery
Background:
- Abnormal QT dispersion (QTd) indicates ventricular action potential inhomogeneity.
- Coronary artery disease (CAD) affects ventricular electrophysiology.
Purpose of the Study:
- To evaluate the short- and long-term effects of coronary artery bypass grafting (CABG) on QT dispersion (QTd).
- To assess QTd at rest and during exercise before and after CABG.
Main Methods:
- QTd measured as max-min QT interval from 12-lead ECG.
- Measurements taken at rest and peak exercise (ET) before, 6 months, and 2 years post-CABG.
- 64 male patients with CAD (mean age 54±10 years) included.
Main Results:
- Significant reduction in rest QTd post-CABG (60±20 ms to 43±14 ms at 6 months, 45±13 ms at 2 years; p<0.001).
- Significant reduction in peak exercise QTd post-CABG (66±22 ms to 38±11 ms at 6 months, 36±11 ms at 2 years; p<0.001).
- Exercise-provoked increase in corrected QT dispersion (QTdc) observed in patients with recurrent ischemia (angina, ST depression) 2 years post-CABG.
Conclusions:
- CABG leads to significant reductions in both rest and exercise QTd.
- QT dispersion measurement during exercise stress testing may aid in identifying post-CABG patients with recurrent ischemia.
Background:
Abnormal dispersion of the QT interval (QTd), measured as the interlead variability of QT, reflects an inhomogeneity of ventricular action potentials. In this study we observed both short- and long-term influences of coronary artery bypass grafting (CABG) on rest and exercise QTd in 64 male patients, having a mean age of 54+/-10 years, with coronary heart disease.
Material/Methods:
QTd was measured as the difference between QT maximum and minimum from 12 leads on an averaged ECG (25 mm/s). QTd and QTdc were measured at rest and at peak exercise during symptom-limited treadmill exercise (ET), which was performed before, 6 months after, and 2 years after CABG.
Results:
There was a significant reduction in rest QTd from before CABG to 6 months and 2 years after (60+/-20 ms vs. 43+/-14 ms and 45+/-13 ms, respectively; p<0.001). Similarly, there was a significant reduction in peak QTd from before CABG to 6 months and 2 years after (66+/-22 ms vs. 38+/-11 ms and 36+/-11 ms, respectively; p<0.001). Two years after CABG, 17 patients had a recurrence of angina and ET provoked chest pain and/or >2 mm ST depression. The resting values did not distinguish patients with ischemia from nonischemic ones. In patients with ischemia, ET provoked an increase in QTdc.
Conclusions:
Rest and exercise QTd is significantly reduced after CABG. It seems that the measurement of QT dispersion during ET can be helpful in distinguishing patients with a recurrence of ischemia.
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