Influence of coronary artery bypass grafting on QT dispersion.

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.