title: QT hysteresis index improves the power of treadmill exercise test in the screening of coronary artery disease.
abstract: BACKGROUND
  QT hysteresis phenomenon exists in healthy subjects, and is more exaggerated in patients with coronary artery disease (CAD) and long QT syndrome. The purpose of this study was to establish an appropriate method to evaluate the magnitude of QT hysteresis, and assess the value of QT hysteresis index in the treadmill exercise test (TET) in predicting CAD. METHODS AND RESULTS: A total of 138 subjects with suspected CAD and referred for TET and selective coronary angiography (SCA) were divided into positive (n=77) and negative (n=61) SCA groups. Dynamic ECG were recorded during TET. QT/RR curves were constructed and QTp (Q-Tpeak) and QTe (Q-Tend) hysteresis indices were calculated for each subject. SYNTAX score in the positive SCA group was determined. The QTp and QTe hysteresis indices in the positive SCA group were significantly higher than in the negative SCA group. The combination of QTe hysteresis index and conventional TET criteria had the highest sensitivity and negative predictive value according to receiver operating characteristic curve, and was an independent predictor on multivariate logistic regression. QT hysteresis indices significantly correlated with SYNTAX score in the positive SCA group.
  
  
  CONCLUSIONS
  QTe hysteresis index enhances the specificity of predicting CAD in TET. It improves the diagnostic value of TET for CAD significantly when combined with conventional criteria and is associated with the severity of CAD.
authors.affiliation: Department of Cardiology, Wuhan University, Renmin Hospital.
authors.forename: Yijie
authors.initials: Y
authors.lastname: Zhang
authors.forename: Mingwei
authors.initials: M
authors.lastname: Bao
authors.forename: Mingyan
authors.initials: M
authors.lastname: Dai
authors.forename: Hui
authors.initials: H
authors.lastname: Zhong
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.forename: Tuantuan
authors.initials: T
authors.lastname: Tan
mesh_terms: D000328:Adult; D017023:Coronary Angiography; D003324:Coronary Artery Disease / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000503:physiopathology; D004562:Electrocardiography / Q000379:methods*; D005080:Exercise Test / Q000379:methods*; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012372:ROC Curve; D012307:Risk Factors