title: Evaluating strict and conventional left bundle branch block criteria using electrocardiographic simulations.
abstract: OBJECTIVE
  Left bundle branch block (LBBB) is a critical predictor of patient benefit from cardiac resynchronization therapy (CRT), but recent studies suggest that one-third of patients diagnosed with LBBB by conventional electrocardiographic (ECG) criteria may have a false-positive diagnosis. In this study, we tested the hypothesis that recently proposed strict LBBB ECG criteria improve specificity in cases of left ventricular hypertrophy (LVH) /dilatation and incomplete LBBB.
  
  
  RESULTS
  We developed five heart models based on a healthy male with increasing degrees of LV hypertrophy and/or dilation. With each model, we simulated six conduction types: normal conduction, four increments of delayed initiation of LV activation (incomplete LBBB), and complete LBBB. Simulated ECGs were evaluated for the presence of LBBB by conventional (LV conduction delay and QRSd ≥120 ms) and strict ECG criteria (LV conduction delay, QRSd ≥140 ms men or ≥130 ms women, and mid-QRS notching in at least two of the leads I, aVL, V1, V2, V5, and/or V6). Both conventional and strict LBBB criteria had 100% sensitivity. However, conventional criteria falsely diagnosed LBBB in cases with LVH + LV dilated 10 mm, LVH or LV dilated 10 mm combined with LV initiation ≥6 ms after the right ventricle (RV), and with LV dilated 5 mm combined with LV initiation ≥12 ms after RV (48% specificity). Strict LBBB criteria resulted in no false positives (100% specificity).
  
  
  CONCLUSIONS
  New strict LBBB criteria increase the specificity of complete LBBB diagnosis in the presence of LV hypertrophy/dilatation and incomplete LBBB, which is critical for selecting CRT patients.
authors.affiliation: Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, U.S. Food and Drug Administration, Silver Spring, MD 20993, USA.
authors.forename: Loriano
authors.initials: L
authors.lastname: Galeotti
authors.forename: Peter M
authors.initials: PM
authors.lastname: van Dam
authors.forename: Zak
authors.initials: Z
authors.lastname: Loring
authors.forename: Dulciana
authors.initials: D
authors.lastname: Chan
authors.forename: David G
authors.initials: DG
authors.lastname: Strauss
mesh_terms: D000328:Adult; D002037:Bundle-Branch Block / Q000175:diagnosis* / Q000503:physiopathology; D058406:Cardiac Resynchronization Therapy; D003198:Computer Simulation; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006333:Heart Failure / Q000175:diagnosis* / Q000503:physiopathology / Q000628:therapy; D006801:Humans; D017379:Hypertrophy, Left Ventricular / Q000175:diagnosis / Q000503:physiopathology; D008279:Magnetic Resonance Imaging; D008297:Male; D008955:Models, Cardiovascular; D018579:Patient Selection; D011237:Predictive Value of Tests; D011379:Prognosis; D016277:Ventricular Function, Left
keywords: Cardiac resynchronization therapy; Electrocardiography; Left bundle branch block; Simulations