title: QRS duration versus morphology and survival after cardiac resynchronization therapy.
abstract: OBJECTIVE
  The prognostic implications of QRS duration and morphology in heart failure patients treated with cardiac resynchronization therapy (CRT) remains debated. The present evaluation investigated the association between QRS duration (<150 vs. ≥150 ms) and QRS morphology (left bundle brand block [LBBB] vs. non-LBBB) and long-term prognosis of a large cohort of unselected heart failure patients treated with CRT according to contemporary guidelines.
  
  
  RESULTS
  Of 973 heart failure patients treated with CRT (mean age 66.1 ± 9.8 years, 76% male), 658 patients (68%) showed QRS duration ≥150 ms, and 772 patients (79%) had LBBB configuration. Compared with patients with QRS duration <150 ms, patients with QRS duration ≥150 ms had less frequently ischaemic cardiomyopathy and atrial fibrillation and showed larger left ventricular volumes and lower left ventricular ejection fraction. Compared with patients with non-LBBB configuration, patients with LBBB morphology were younger, less often males and less often had ischaemic cardiomyopathy and atrial fibrillation. On multivariable analysis, after correcting for relevant clinical and echocardiographic variables, LBBB morphology was significantly associated with better survival [hazard ratio (HR) 0.737; 95% confidence interval (CI) 0.584-0.931;P= 0.010], whereas there was no statistically significant association between QRS duration ≥150 ms and survival (HR 0.889; 95% CI 0.726-1.088;P= 0.252).
  
  
  CONCLUSIONS
  In this large population of heart failure patients treated with CRT, QRS morphology was independently associated with long-term survival. The association between QRS duration and long-term survival was not statistically significant.
authors.affiliation: Heart Lung Center Leiden University Medical Center Leiden The Netherlands.
authors.forename: Mand J H
authors.initials: MJ
authors.lastname: Khidir
authors.affiliation: Heart Lung Center Leiden University Medical Center Leiden The Netherlands.
authors.forename: Victoria
authors.initials: V
authors.lastname: Delgado
authors.affiliation: Heart Lung Center Leiden University Medical Center Leiden The Netherlands.
authors.forename: Nina
authors.initials: N
authors.lastname: Ajmone Marsan
authors.affiliation: Heart Lung Center Leiden University Medical Center Leiden The Netherlands.
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Schalij
authors.affiliation: Heart Lung Center Leiden University Medical Center Leiden The Netherlands.
authors.forename: Jeroen J
authors.initials: JJ
authors.lastname: Bax
keywords: Cardiac resynchronization therapy; Left bundle branch block; Prognosis; QRS duration