title: QT restitution properties during exercise in male patients with coronary artery disease.
abstract: BACKGROUND
  The hypothesis of action potential duration restitution (APDR) suggests that wave break is mainly determined by the steepness of APDR curve. The purpose of this study was to investigate the QT restitution properties by a noninvasive method, exercise ECG test, in patients with and without left anterior descending coronary artery disease (CAD).
  
  
  METHODS
  Twenty-six male patients were divided into CAD group and control group based on the result of selective coronary angiography (SCA). Exercise tests were performed in each case before the SCA. Sequential QT intervals and preceding TQ intervals were measured, and QT restitution curve (QTRC) was constructed by plotting QT versus TQ intervals.
  
  
  RESULTS
  Within the physiological maximal heart rate, the maximal slope of QTRC in the CAD group (1.40 ± 0.41) was greater than that in the control group (0.84 ± 0.20, P = 0.002). The mean slope values of the CAD group was also statistically higher than that in the control group at the same TQ levels when the TQ interval decreased to less than 250 ms (P < 0.05). CAD patients had lower linear correlation coefficients of QT/TQ compared with the control group (0.86 ± 0.04 in the CAD group vs 0.91 ± 0.02 in the control group, P < 0.001).
  
  
  CONCLUSIONS
  Male patients with left anterior descending CAD had steeper QTRC than those without CAD. QTRC from exercise test ECG may be an effective noninvasive method for estimating the electrophysiological restitution properties of the ventricle.
authors.forename: Dongdong
authors.initials: D
authors.lastname: Zhao
authors.forename: Yidong
authors.initials: Y
authors.lastname: Wei
authors.forename: Kai
authors.initials: K
authors.lastname: Tang
authors.forename: Xuejing
authors.initials: X
authors.lastname: Yu
authors.forename: Jing
authors.initials: J
authors.lastname: Wen
authors.forename: Jingying
authors.initials: J
authors.lastname: Zhang
authors.forename: Yawei
authors.initials: Y
authors.lastname: Xu
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000328:Adult; D016022:Case-Control Studies; D017023:Coronary Angiography; D003327:Coronary Disease / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000534:rehabilitation*; D004562:Electrocardiography; D005080:Exercise Test; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged