Abstract
BackgroundQT dispersion (QTd) is related to regional variations in myocardial repolarization. Our study aims to assess the value of QTd in prediction of myocardial ischemia and its severity during stress imaging.We enrolled one hundred patients having stable coronary artery disease (CAD) and fulfilling the “Appropriateness criteria for cardiac radionuclide imaging” (MPI). They were divided into group I including patients with MPI-detected ischemia (50 patients) and group II including patients with normal perfusion scan (50 patients). We excluded unstable CAD and all other causes affecting QTd. During isotope scan, ECGs were taken and QTd was calculated at rest and at maximum heart rate.ResultsQTd was significantly higher in the ischemic group both at rest and exercise (P = 0.000). QTd difference, the difference between QTd at rest and stress, was calculated. QTd difference was significantly lower in normal than in ischemic group (P = 0.003). There was a significant positive correlation between QTd difference and defect size (P = 0.04).ConclusionQTd increases in ischemia and the QTd difference (between rest and stress) correlates positively with severity of ischemia.QTd and QTd difference could be used to improve the accuracy of stress imaging test.
Highlights
QT dispersion (QTd) is related to regional variations in myocardial repolarization
We aim to investigate the correlation between QTd, during rest and maximum exercise ECG, and the severity and extent of myocardial ischemia detected by myocardial perfusion imaging technique
The mean (± SD) QTds at rest for patients with normal myocardium and those with myocardial ischemia detected by Myocardial perfusion imaging (MPI) were 15.7 (± 5.2) ms and 34.24 (± 13.91) ms [P = 0.0000] indicating high significant value
Summary
QT dispersion (QTd) is related to regional variations in myocardial repolarization. We enrolled one hundred patients having stable coronary artery disease (CAD) and fulfilling the “Appropriateness criteria for cardiac radionuclide imaging” (MPI). They were divided into group I including patients with MPI-detected ischemia (50 patients) and group II including patients with normal perfusion scan (50 patients). In 1990, Day CP et al [2] coined the term QT dispersion and concluded that it was related to regional variations in myocardial repolarization in ECG. Clinical and experimental data have shown that QT interval prolongation measured from the standard 12lead ECG is a risk factor for ventricular arrhythmia and sudden death in patients with and those without previous acute myocardial infarction (AMI). There is further strong support for the hypothesis that interlead variations in QT interval reflect regional variations in ventricular repolarization, and increased dispersion of ventricular (2021) 73:5 recovery time is believed to provide a substrate that supports serious ventricular arrhythmias [4]
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