title: New or presumably new left bundle branch block in patients with suspected acute coronary syndrome: Clinical, echocardiographic, and electrocardiographic features from a single-center registry.
abstract: BACKGROUND
  In patients with suspected acute coronary syndrome, a new or presumably new left bundle branch block (LBBB) does not always imply ST-segment elevation myocardial infarction (STEMI). We aimed to show the low frequency of STEMI-equivalent in this population and determine the diagnostic value of electrocardiographic and echocardiographic features.
  
  
  METHODS
  From the 387 patients captured by the Louisiana State University code STEMI registry between 2009 and 2012, we examined data on 26 patients with LBBB. These patients were divided into 3 groups according to the final diagnosis: (1) STEMI-equivalent, defined as an acute coronary occlusion on angiography (2 patients), (2) non-ST-segment elevation myocardial infarction (4 patients), and (3) diagnoses other than myocardial infarction (non-MI) (20 patients).
  
  
  RESULTS
  Troponin elevation and left ventricular systolic dysfunction were common in all 3 groups (non-significant p-values). Compared with non-MI patients, patients with STEMI-equivalent had a larger degree of ST-segment discordance and T-wave discordance, as assessed by ST/QRS and T/QRS ratios (p<0.001). ST/QRS ratio ≥ 0.2 and T/QRS ratio ≥ 0.5 were sensitive and specific for the diagnosis of STEMI-equivalent in the setting of LBBB. Conversely, absolute values of ST-segment and T-wave discordance were not significantly different between groups. ST-segment concordance was highly specific for the diagnosis of STEMI-equivalent, but had a limited sensitivity.
  
  
  CONCLUSIONS
  Only a minority of patients with suspected acute coronary syndrome and LBBB have a STEMI-equivalent. Excessive relative discordance of the ST segment or the T wave appears predictive of STEMI-equivalent, but this is only hypothesis-generating considering the small population size.
authors.affiliation: Department of Medicine, Cardiovascular Section, Louisiana State University, New Orleans, LA, USA. Electronic address: ehanna@lsuhsc.edu.
authors.forename: Elias B
authors.initials: EB
authors.lastname: Hanna
authors.affiliation: Cardiovascular Section, University Medical Center, Lafayette, LA.
authors.forename: Viral N
authors.initials: VN
authors.lastname: Lathia
authors.affiliation: Department of Medicine, Cardiovascular Section, Louisiana State University, New Orleans, LA, USA.
authors.forename: Murtuza
authors.initials: M
authors.lastname: Ali
authors.affiliation: Department of Medicine, University Hospital of Geneva, Geneva, Switzerland.
authors.forename: Eliana Hanna
authors.initials: EH
authors.lastname: Deschamps
mesh_terms: D054058:Acute Coronary Syndrome / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology*; D000368:Aged; D015415:Biomarkers / Q000097:blood; D002037:Bundle-Branch Block / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology*; D015984:Causality; D015897:Comorbidity; D004452:Echocardiography / Q000706:statistics & numerical data*; D004562:Electrocardiography / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008145:Louisiana / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012042:Registries; D015203:Reproducibility of Results; D012307:Risk Factors; D012680:Sensitivity and Specificity; D019210:Troponin I / Q000097:blood
chemical_list: D015415:Biomarkers; D019210:Troponin I
keywords: Discordant ST segment; Discordant T wave; Left bundle branch block; ST-segment elevation myocardial infarction