QT dispersion in comparison to Tl-201-SPECT for detection of myocardial ischaemia

Objective There is controversy whether the measurement of QT dispersion might provide information about the presence and extent of ischaemic myocardium. It was the aim to analyse the diagnostic value of QT dispersion for the detection of myocardial ischaemia in comparison to Tl-201-SPECT. Patients and methods 100 patients were randomly selected from patients referred for Tl-201-SPECT. QT duration was measured in all 12 leads in the resting ECG and in the ECG either at maximal bicycle exercise or during peak dipyridamole stress. QT dispersion was calculated and correlated with parameters of ischaemia for all patients and for the bicycle exercise and the dipyridamole group separately. Results 25 patients had to be excluded from the analysis because QT dispersion could not be measured. Regression analysis did not show significant correlation neither for all 75 patients nor for the bicycle exercise nor for the dipyridamole group correlating grade of myocardial ischaemia, number of ischaemic segments and summed ischaemic stress score with QT dispersion in the resting or the stress ECG and QTd and there was no significant difference between groups. Conclusion QT dispersion could not be measured in 25/100 patients (25%). In the remaining patients QT dispersion did not correlate with the extent or grade of myocardial ischaemia.