title: Identification of Typical Left Bundle Branch Block Contraction by Strain Echocardiography Is Additive to Electrocardiography in Prediction of Long-Term Outcome After Cardiac Resynchronization Therapy.
abstract: BACKGROUND
  Current guidelines suggest that patients with left bundle branch block (LBBB) be treated with cardiac resynchronization therapy (CRT); however, one-third do not have a significant activation delay, which can result in nonresponse. By identifying characteristic opposing wall contraction, 2-dimensional strain echocardiography (2DSE) may detect true LBBB activation.
  
  
  OBJECTIVE
  This study sought to investigate whether the absence of a typical LBBB mechanical activation pattern by 2DSE was associated with unfavorable long-term outcome and if this is additive to electrocardiographic (ECG) morphology and duration.
  
  
  METHODS
  From 2 centers, 208 CRT candidates (New York Heart Association classes II to IV, ejection fraction ≤35%, QRS duration ≥120 ms) with LBBB by ECG were prospectively included. Before CRT implantation, longitudinal strain in the apical 4-chamber view determined whether typical LBBB contraction was present. The pre-defined outcome was freedom from death, left ventricular assist device, or heart transplantation over 4 years.
  
  
  RESULTS
  Two-thirds of patients (63%) had a typical LBBB contraction pattern. During 4 years, 48 patients (23%) reached the primary endpoint. Absence of a typical LBBB contraction was independently associated with increased risk of adverse outcome after adjustment for ischemic heart disease and QRS width (hazard ratio [HR]: 3.1; 95% CI: 1.64 to 5.88; p < 0.005). Adding pattern assessment to a risk prediction model including QRS duration and ischemic heart disease significantly improved the net reclassification index to 0.14 (p = 0.04) and improved the C-statistics (0.63 [95% CI: 0.54 to 0.72] vs. 0.71 [95% CI: 0.63 to 0.80]; p = 0.02). Use of strict LBBB ECG criteria was not independently associated with outcome in the multivariate model (HR: 1.72; 95% CI: 0.89 to 3.33; p = 0.11. Assessment of LBBB contraction pattern was superior to time-to-peak indexes of dyssynchrony (p < 0.01 for all).
  
  
  CONCLUSIONS
  Contraction pattern assessment to identify true LBBB activation provided important prognostic information in CRT candidates.
authors.affiliation: Department of Cardiology, Rigshospitalet Copenhagen University Hospital, Copenhagen, Denmark. Electronic address: nielsrisum@gmail.com.
authors.forename: Niels
authors.initials: N
authors.lastname: Risum
authors.affiliation: Division of Cardiology, University of Pittsburgh, Pittsburgh, Pennsylvania; Department of Cardiology and Clinical Medicine, Aalborg University Hospital, Aalborg, Denmark.
authors.forename: Bhupendar
authors.initials: B
authors.lastname: Tayal
authors.affiliation: Department of Cardiology, Gentofte University Hospital, Hellerup, Denmark.
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Hansen
authors.affiliation: Division of Cardiology, University of Pittsburgh, Pittsburgh, Pennsylvania; Department of Cardiology, Gentofte University Hospital, Hellerup, Denmark.
authors.forename: Niels E
authors.initials: NE
authors.lastname: Bruun
authors.affiliation: Department of Cardiology, Holbæk Hospital, Holbæk, Denmark.
authors.forename: Magnus T
authors.initials: MT
authors.lastname: Jensen
authors.affiliation: Department of Cardiology, Gentofte University Hospital, Hellerup, Denmark.
authors.forename: Trine K
authors.initials: TK
authors.lastname: Lauridsen
authors.affiliation: Division of Cardiology, University of Pittsburgh, Pittsburgh, Pennsylvania.
authors.forename: Samir
authors.initials: S
authors.lastname: Saba
authors.affiliation: Division of Cardiovascular Medicine, Duke University Medical Center, Durham, North Carolina.
authors.forename: Joseph
authors.initials: J
authors.lastname: Kisslo
authors.affiliation: Division of Cardiology, University of Pittsburgh, Pittsburgh, Pennsylvania.
authors.forename: John
authors.initials: J
authors.lastname: Gorcsan
authors.affiliation: Department of Cardiology and Clinical Medicine, Aalborg University Hospital, Aalborg, Denmark.
authors.forename: Peter
authors.initials: P
authors.lastname: Sogaard
mesh_terms: D000368:Aged; D002037:Bundle-Branch Block / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000628:therapy*; D058406:Cardiac Resynchronization Therapy / Q000379:methods / Q000639:trends*; D004452:Echocardiography / Q000639:trends; D004562:Electrocardiography / Q000639:trends*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D013997:Time Factors; D016896:Treatment Outcome
keywords: 2-dimensional strain echocardiography; defibrillator; heart failure; multivariate analysis; prognosis; prospective studies