Can QT dispersion improve the accuracy of stress ECG TMT in detecting myocardial ischemia in chronic stable CAD patients? A stress myocardial perfusion imaging study

Abstract

Background QT 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. Results QTd 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). Conclusion QTd 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.

Correlation between QT Interval Prolongation or Dispersion in Positive Exercise ECG Patients and severity of coronary artery disease

“…In the current work, correlation analysis reported positive correlation between Gensini score (degree of coronary obstruction) and QT interval (at beginning, at peak & at recovery), corrected QT, QT dispersion at peak. This is in agreement with the result found by (11) who found a positive association between QT dispersion difference and cardiac defect size, also another study (21) that also showed that a strongly positive association exists between QTc dispersion and SYNTAX score (degree of coronary occlusion). Also, various studies reported the association between QTc dispersion and CAD severity (22, 23 & 24) Nevertheless, these investigations assessed the severity of CAD utilizing distinct grading methods, including vessel score, Friesinger score, and Leaman score, but the study (25) assessed extent and severity of ischemia by diffuse score and Gensini score.…”

“…Also, another study (9) reported significantly higher QTc among obstructive CAD patients than non-obstructive CAD This work revealed that QT dispersion at rest had significantly lower value in normal group than both non obstructive and obstructive CAD groups and also a significantly lower QT dispersion was present in non-obstructive than obstructive CAD groups. Coincident results presented in study (11) that revealed that QT dispersion at rest and at peak of stress ECG were considerably higher in ischemic cases than normal perfusion group.…”

“…If the end of the T-wave is not visible, such as when it is fused with the U-wave or P-wave as in the case of rapid heart rate, a straight line is drawn tangential to the downstroke of the T-wave until it meets the base line (identified from the level of the PR segment) and this is considered the end of the T-wave. Difference between the highest and the lowest QT is QTd (11) .…”

Mitral valve prolapse—arrhythmic faces of the valve disease

“…This large difference between the maximum and minimum QT corrected (QTc) for heart rate reflects both the reduction and increase of repolarization intervals. It could be explained by increased wall stress or regional ischemia [32]. Other ECG changes were observed in Rs or rS waves, visible in inferior or in I and aVL leads, however, they require further research [28].…”