title: Among patients with left bundle branch block, T-wave peak to T-wave end time is prolonged in the presence of acute coronary occlusion.
abstract: BACKGROUND
  Assessing the effect of myocardial ischemia on ventricular repolarization in the setting of left bundle branch block (LBBB) poses a challenge due to secondary prolongation of the QT interval inherent in LBBB. The T-wave peak to T-wave end (TpTe) interval has been noted to prolong during myocardial ischemia and correct after reperfusion in patients with normal conduction. Here we compare the TpTe intervals of patients with LBBB both with and without complete acute coronary occlusion (ACO).
  
  
  METHODS
  Retrospectively, emergency department patients with LBBB and symptoms of myocardial ischemia were identified both with angiographically-proven ACO and with No-ACO. The longest QT, JT, and TpTe intervals were analyzed.
  
  
  RESULTS
  The ACO and No-ACO groups consisted of 33 and 129 patients, respectively. The mean TpTe was longer in ACO (103.6ms [95%CI 98.5-108.7]) compared to No-ACO patients (88.6ms [95%CI 85.3-91.9]) (P<0.0001) and this held true after correction for heart rate. In ACO versus No-ACO, the TpTe also more frequently exceeded prolongation cutoffs of 85ms (30 [90%] versus 69 [54%]) and 100ms (25 [76%] versus 42 [33%]) (P<0.0001 for all). The mean QT, JT, QTc, and JTc intervals were not significantly different between the groups for either the Bazett's or Rautaharju's correction formulas.
  
  
  CONCLUSIONS
  In patients with LBBB on the ECG, the TpTe is longer and more frequently prolonged in patients with ACO compared to patients without ACO. Future studies of ventricular repolarization in patients with LBBB should include analyses of the TpTe interval.
authors.affiliation: Department of Emergency Medicine, Hennepin County Medical Center, Division of Critical Care Medicine, Department of Medicine, Hennepin County Medical Center, United States. Electronic address: KDoddMD@gmail.com.
authors.forename: Kenneth W
authors.initials: KW
authors.lastname: Dodd
authors.affiliation: Department of Emergency Medicine, Hennepin County Medical Center, United States.
authors.forename: Kendra D
authors.initials: KD
authors.lastname: Elm
authors.affiliation: University of Minnesota Medical School, United States.
authors.forename: Erin M
authors.initials: EM
authors.lastname: Dodd
authors.affiliation: Department of Emergency Medicine, Hennepin County Medical Center, Department of Emergency Medicine, University of Minnesota Medical School, United States.
authors.forename: Stephen W
authors.initials: SW
authors.lastname: Smith
mesh_terms: D000368:Aged; D002037:Bundle-Branch Block / Q000175:diagnosis / Q000503:physiopathology; D017023:Coronary Angiography / Q000379:methods; D054059:Coronary Occlusion / Q000175:diagnosis / Q000503:physiopathology; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006329:Heart Conduction System / Q000000981:diagnostic imaging* / Q000503:physiopathology; D006352:Heart Ventricles / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results
keywords: Coronary occlusion; JT interval; Left bundle branch block; Myocardial infarction; QT interval; T-wave peak-to-end interval; Ventricular repolarization