title: New-onset left bundle branch block-associated idiopathic nonischemic cardiomyopathy and left ventricular ejection fraction response to guideline-directed therapies: The NEOLITH study.
abstract: BACKGROUND
  Left ventricular ejection fraction (LVEF) response to guideline-directed medical therapy (GDMT) and to early cardiac resynchronization therapy (CRT) in new-onset idiopathic nonischemic cardiomyopathy (NICM) and left bundle branch block (LBBB) is not well described. CRT is recommended if LVEF remains ≤35% after at least 3 months of GDMT.
  
  
  OBJECTIVE
  The purpose of this study was to describe LVEF response to GDMT at 3 months and to early CRT in new-onset LBBB-associated idiopathic NICM.
  
  
  METHODS
  A retrospective cohort study was performed in subjects with new-onset idiopathic NICM, LVEF ≤35%, and LBBB or narrow (<120 ms) QRS complex morphology. LVEF response between groups was evaluated with log-binomial and linear regression. LVEF response within groups was evaluated using the paired Student t test.
  
  
  RESULTS
  In 102 subjects (70 with narrow QRS complex and 32 with LBBB), post-GDMT LVEF was >35% in 39 narrow QRS complex subjects (56%) and 2 LBBB subjects (6%) (P < .0001). The absolute difference between post-GDMT LVEF and initial LVEF was greater in the narrow QRS complex group (16.1% ± 14.6% vs. 3.3% ± 10.7%; P < .0001). Narrow QRS complex, referenced to LBBB, was significantly associated with post-GDMT LVEF >35% (relative risk 10.30; 95% confidence interval 2.63-40.27; P = .0008) and absolute difference between post-GDMT LVEF and initial LVEF (β = 16.296; standard error = 2.977; P < .0001) in final multivariable analyses. CRT super-response, defined as post-CRT LVEF ≥50%, was observed in 8 of LBBB subjects (35%) who received CRT.
  
  
  CONCLUSIONS
  GDMT did not significantly improve LVEF in new-onset LBBB-associated idiopathic NICM at 3 months. Most remained candidates for CRT, and a high percentage were super-responders. Optimal timing for CRT implantation requires further investigation.
authors.affiliation: Heart and Vascular Institute, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania. Electronic address: wangnc@upmc.edu.
authors.forename: Norman C
authors.initials: NC
authors.lastname: Wang
authors.affiliation: Heart and Vascular Institute, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.
authors.forename: Madhurmeet
authors.initials: M
authors.lastname: Singh
authors.affiliation: Heart and Vascular Institute, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.
authors.forename: Evan C
authors.initials: EC
authors.lastname: Adelstein
authors.affiliation: Heart and Vascular Institute, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.
authors.forename: Sandeep K
authors.initials: SK
authors.lastname: Jain
authors.affiliation: Heart and Vascular Institute, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.
authors.forename: G Stuart
authors.initials: GS
authors.lastname: Mendenhall
authors.affiliation: Heart and Vascular Institute, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.
authors.forename: Alaa A
authors.initials: AA
authors.lastname: Shalaby
authors.affiliation: Heart and Vascular Institute, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.
authors.forename: Andrew H
authors.initials: AH
authors.lastname: Voigt
authors.affiliation: Heart and Vascular Institute, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.
authors.forename: Samir
authors.initials: S
authors.lastname: Saba
mesh_terms: D000368:Aged; D002037:Bundle-Branch Block / Q000209:etiology / Q000503:physiopathology / Q000628:therapy*; D058406:Cardiac Resynchronization Therapy / Q000592:standards*; D009202:Cardiomyopathies / Q000150:complications* / Q000503:physiopathology / Q000628:therapy; D004452:Echocardiography; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D019983:Guideline Adherence; D006329:Heart Conduction System / Q000503:physiopathology; D006352:Heart Ventricles / Q000000981:diagnostic imaging / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013318:Stroke Volume / Q000502:physiology*; D013997:Time Factors; D016896:Treatment Outcome
keywords: Cardiac resynchronization therapy; Left bundle branch block; Medications; Nonischemic cardiomyopathy