[QT dispersion in surface ECG and QT dynamics in long-term ECG in patients with coronary heart disease in the chronic post-infarct stage with and without ventricular tachyarrhythmias--correlation with other risk parameters]

Abstract

QT-dispersion (QTD) in 12-lead surface-ECG and QT-dynamics in Holter-ECG, defined as the time-course of the frequency corrected QT-interval (mQTc), were determined in 42 patients with coronary artery disease in chronic postinfarction stadium without ventricular tachyarrhythmias (CAD/VTA-) and in 24 CAD patients with ventricular tachyarrhythmias (CAD/VTA+). 14 healthy volunteers served as control group (CG). Correlations with hemodynamic data (LVEF, severity of CAD) and with other risk-parameters (ventricular late potentials, short-time heart rate variability) were calculated. QTD in CAD/VTA-was significantly higher compared to CG (48.4 ms+/- 19.6 vs 31.4 ms +/- 9.8, p < 0.05). There were no intergroup differences in QT-dynamics. CAD/VTA+ patients showed the highest QTD-values (59.5 ms +/- 31.1, p < 0.05 compared to CG/CAD/VTA0) and a significantly altered QT-dynamics compared to CG/CAD/VTA- (mQTc: 431.3 ms +/- 38.8 vs 400.8 ms +/- 25.5 vs 406.3 ms +/- l0.6, p < 0.05). Only parameters of QTD were significantly correlated to severity of CAD (r = +0.41, p < 0.01) and to LVEF (r = 0.43, p < 0.01). We did not find significant correlations between the parameters of QT-dispersion/QT-dynamics among one another and to the risk-parameters. These results indicate that the QT-dispersion in CAD-patients also in chronic post-infarction stadium is elevated and that CAD-patients with VTA are characterized by an altered QT-dynamics. Parameters of both methods are independent of other validated risk-parameters. So the measurement of QT-dispersion and QT-dynamics as markers of inhomogenous repolarization could contribute to an improvement of risk-stratification of CAD-patients.