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QT dispersion in comparison to Tl-201-SPECT for detection of myocardial ischaemia
Matthias Schmidt1, Christian Schneider, Peter Theissen
1Department of Nuclear Medicine, University of Cologne, Germany. Matthias.Schmidt@uni-koeln.de
Insights
QT dispersion measurement was unreliable in 25% of patients. In the remaining individuals, QT dispersion did not correlate with myocardial ischaemia, limiting its diagnostic value for detecting ischaemic heart disease.
Area of Science:
- Cardiology
- Diagnostic Imaging
- Electrophysiology
Background:
- The diagnostic utility of QT dispersion for assessing myocardial ischaemia remains controversial.
- QT dispersion is a measure of repolarization heterogeneity on the electrocardiogram (ECG).
- Thallium-201 single-photon emission computed tomography (Tl-201 SPECT) is a standard for evaluating myocardial ischaemia.
Purpose of the Study:
- To evaluate the diagnostic value of QT dispersion in detecting myocardial ischaemia.
- To compare the effectiveness of QT dispersion with Tl-201 SPECT.
Main Methods:
- 100 patients referred for Tl-201 SPECT were randomly selected.
- QT duration was measured from 12-lead ECGs at rest and during stress (bicycle exercise or dipyridamole).
- QT dispersion was calculated and correlated with ischaemia parameters.
Main Results:
- QT dispersion could not be reliably measured in 25% of patients.
- No significant correlation was found between QT dispersion and the grade or extent of myocardial ischaemia in the remaining 75 patients.
- No significant differences in QT dispersion were observed between exercise and dipyridamole stress groups.
Conclusions:
- QT dispersion measurement is not consistently feasible.
- QT dispersion does not correlate with myocardial ischaemia extent or grade.
- QT dispersion is not a reliable non-invasive marker for detecting myocardial ischaemia in this patient cohort.
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.
