title: Baseline delayed left ventricular activation predicts long-term clinical outcome in cardiac resynchronization therapy recipients.
abstract: OBJECTIVE
  We undertook this analysis to assess the relationship between delayed left ventricular activation time (LVAT), assessed prior to cardiac resynchronization therapy (CRT), with the long-term clinical outcomes in CRT recipients. We also sought to determine if baseline LVAT had similar predictive value in patients who were versus were not chronically paced prior to CRT.
  
  
  RESULTS
  Baseline pre-implant electrocardiograms (ECGs) of 219 consecutive patients undergoing CRT were analysed. Of these, 68 (31%) were chronically right ventricular (RV)-paced pre-CRT. Maximum LVAT was measured as QRS-duration minus time from QRS onset to the first notch in the QRS. Cox models were used to assess the association between LVAT and clinical outcome (death or cardiac transplant). Over a median follow-up of 56 months, 92 patients (42%) died and 10 (5%) underwent cardiac transplant. In the non-RV-paced group an independent linear relationship between LVAT and outcome [hazard ratio (HR) 0.67 per 50 ms increase in LVAT; 95% confidence interval (CI) 0.46-0.99] was observed. An LVAT ≥ 125 ms was associated with a markedly lower risk of outcome (adjusted HR 0.51; 95% CI 0.30-0.86) in these patients. Despite a similar incidence of death or cardiac transplantation in the RV-paced group vs. the non-paced one, no significant association between LVAT and outcome was observed in the RV-paced group.
  
  
  CONCLUSIONS
  Baseline LVAT, a simple ECG measure, independently predicts long-term outcome with CRT in non-RV paced patients. However, prolonged LVAT is not associated with an altered prognosis in patients chronically RV paced prior to CRT.
authors.affiliation: Libin Cardiovascular Institute of Alberta, Calgary, AB, Canada. charlotteeitel@gmx.de
authors.forename: Charlotte
authors.initials: C
authors.lastname: Eitel
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Wilton
authors.forename: Noah
authors.initials: N
authors.lastname: Switzer
authors.forename: Karen
authors.initials: K
authors.lastname: Cowan
authors.forename: Derek V
authors.initials: DV
authors.lastname: Exner
mesh_terms: D000368:Aged; D001145:Arrhythmias, Cardiac / Q000628:therapy*; D058406:Cardiac Resynchronization Therapy; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011379:Prognosis; D016896:Treatment Outcome; D018487:Ventricular Dysfunction, Left / Q000628:therapy*