title: [Value of QT hysteresis during treadmill exercise test for diagnosing coronary heart disease].
abstract: OBJECTIVE
  To investigate the value of QT hysteresis index during treadmill exercise test (TET) in diagnosing coronary heart disease (CHD).
  
  
  METHODS
  One hundred consecutive patients suspected for CHD were referred for TET and selective coronary angiography (CAG). Patients were divided into positive [n = 55, age (56.0 ± 7.9) years] and negative [n = 45, age (53.2 ± 6.7) years] group based on their CAG results. For each TET recording, 50 points were selected for the RR, QTp, and QTe interval measurements. QTp and QTe interval was plotted against corresponding RR interval. QT/RR curve was constructed by connect all point, QT hysteresis index was calculated for each patient.
  
  
  RESULTS
  The QTp [(22.4 ± 10.3) ms vs. (6.7 ± 4.6) ms, P < 0.001] and QTe [(27.1 ± 11.1) ms vs. (7.6 ± 4.6) ms, P < 0.001] hysteresis index of patients in positive group were significantly higher than those in negative group. The sensitivity of QTp and QTe hysteresis index for diagnosing CHD was 89.1% (49/55) and 94.5% (52/55), respectively, and the specificity was 82.2% (37/45) and 80.0% (36/45), respectively. If the patient fulfilled both the classical TET and QT hysteresis criteria, the sensitivity for diagnosing CHD increased to 94.3% (33/35, QTp) and 94.6% (35/37, QTe), and the specificity were both 100% (26/26, 26/26). Moreover, QTp (r = -0.399, P < 0.001) and QTe (r = -0.547, P < 0.001) hysteresis index highly correlated to Duke treadmill score.
  
  
  CONCLUSIONS
  QT hysteresis index is useful parameter for CHD diagnosis and which could improve the diagnostic value of TET for CHD in combination with the classical TET criteria for diagnosis of CHD.
authors.affiliation: Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan 430060, China. sanko747@yahoo.com.cn
authors.forename: Ming-wei
authors.initials: MW
authors.lastname: Bao
authors.forename: Yi-jie
authors.initials: YJ
authors.lastname: Zhang
authors.forename: Tuan-tuan
authors.initials: TT
authors.lastname: Tan
authors.forename: Ji-ning
authors.initials: JN
authors.lastname: Zhou
authors.forename: Jian-xue
authors.initials: JX
authors.lastname: Yang
authors.forename: Fang
authors.initials: F
authors.lastname: Wang
authors.forename: Fei
authors.initials: F
authors.lastname: Ha
mesh_terms: D000328:Adult; D000368:Aged; D003327:Coronary Disease / Q000175:diagnosis* / Q000503:physiopathology*; D004562:Electrocardiography / Q000379:methods; D005080:Exercise Test; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D012680:Sensitivity and Specificity