title: Comparison of the QRS Complex, ST-Segment, and T-Wave Among Patients with Left Bundle Branch Block with and without Acute Myocardial Infarction.
abstract: BACKGROUND
  The modified Sgarbossa criteria have been validated as a rule for diagnosis of acute coronary occlusion (ACO) in left bundle branch block (LBBB). However, no analysis has been done on differences in the QRS complex, T-wave, or ST-segment concordance of < 1 mm in the derivation or validation studies. Furthermore, there was no comparison of patients with acute myocardial infarction (AMI) but without ACO (i.e., non-ST-elevation myocardial infarction [non-STEMI]) to patients with ACO or without AMI (no MI).
  
  
  OBJECTIVE
  We compare findings involving the QRS amplitude, ST-segment morphology, ST-concordance < 1 mm, and T-waves in patients with LBBB with ACO, non-STEMI, and no MI.
  
  
  METHODS
  Retrospectively, emergency department patients were identified with LBBB and ischemic symptoms but no MI, with angiographically proven ACO, and with non-STEMI.
  
  
  RESULTS
  ACO, non-STEMI, and no MI groups consisted of 33, 24, and 105 patients. The sum of the maximum deflection of the QRS amplitude across all leads (ΣQRS) was smaller in patients with ACO than those without ACO (101.5 mm vs. 132.5 mm; p < 0.0001) and a cutoff of ΣQRS < 90 mm was 92% specific. For ACO, non-concave ST-segment morphology was 91% specific, any ST concordance ≥ 1 mm was 95% specific, and any ST concordance ≥ 0.5 mm was 94% sensitive. For non-STEMI, terminal T-wave concordance, analogous to biphasic T-waves, was moderately sensitive at 79%.
  
  
  CONCLUSIONS
  We found differences in QRS amplitude, ST-segment morphology, and T-waves between patients with LBBB and ACO, non-STEMI, and no MI. However, none of these criteria outperformed the modified Sgarbossa criteria for diagnosis of ACO in LBBB.
authors.affiliation: Department of Emergency Medicine, Hennepin County Medical Center, Minneapolis, Minnesota; Department of Internal Medicine, Hennepin County Medical Center, Minneapolis, Minnesota.
authors.forename: Kenneth W
authors.initials: KW
authors.lastname: Dodd
authors.affiliation: Department of Emergency Medicine, Hennepin County Medical Center, Minneapolis, Minnesota; Department of Emergency Medicine, University of Minnesota Medical School, Minneapolis, Minnesota.
authors.forename: Kendra D
authors.initials: KD
authors.lastname: Elm
authors.affiliation: Department of Emergency Medicine, Hennepin County Medical Center, Minneapolis, Minnesota; Department of Emergency Medicine, University of Minnesota Medical School, Minneapolis, Minnesota.
authors.forename: Stephen W
authors.initials: SW
authors.lastname: Smith
mesh_terms: D000368:Aged; D002037:Bundle-Branch Block / Q000175:diagnosis*; D003661:Decision Support Techniques; D004502:Education, Medical, Continuing / Q000379:methods; D004562:Electrocardiography / Q000379:methods*; D004636:Emergency Service, Hospital / Q000458:organization & administration / Q000592:standards; D005260:Female; D006329:Heart Conduction System / Q000293:injuries; D006801:Humans; D008297:Male; D009203:Myocardial Infarction / Q000175:diagnosis*; D012189:Retrospective Studies
keywords: QRS complex; ST-segment; T-wave; acute myocardial infarction; left bundle branch block