title: Electrical delay in apically positioned left ventricular leads and clinical outcome after cardiac resynchronization therapy.
abstract: BACKGROUND
  In recent studies, an anatomical apical left ventricular (LV) lead pacing location has been associated with deleterious outcome after cardiac resynchronization therapy (CRT). The differential impact of the LV lead electrical location in these patients remains unknown.
  
  
  RESULTS
  Thirty-one consecutive CRT patients (mean age 71.7 ± 12.7 years, 55% left bundle-branch block [LBBB] morphology) with an apical LV lead and LV lead electrical delay (LVLED) were studied. Anatomical LV lead location was determined via review of coronary venography and chest radiographs. Electrical location was assessed through intraprocedural LVLED measurement. Patients were dichotomized into either "long" LVLED (LVLED ≥ 50% of QRS) or "short" LVLED groups (LVLED < 50%). Patients in the long LVLED group demonstrated significantly greater freedom from a primary composite endpoint of all-cause death, heart failure hospitalization, and cardiac transplantation at 2 years (81% vs 30%, P = 0.007 vs short LVLED patients). Longer LVLED was also associated with more favorable LV remodeling (LV end-systolic volume -41.9 ± 10.3 mL vs -4.3 ± 17.2 mL; P = 0.05), and greater improvement in LV ejection fraction (+9.4 ± 2.9% vs +2.3 ± 7.5%; P = 0.04). Even after multivariate adjustment, LVLED remained an independent predictor of the primary composite endpoint (HR 0.47, P = 0.031).
  
  
  CONCLUSIONS
  Electrical lead localization, as estimated by LVLED ≥ 50%, is associated with improved long-term clinical outcome and measures of LV remodeling in patients with apical LV leads. Intraprocedural LVLED assessment may provide incremental utility in targeting lead placement even in conventionally unfavorable anatomical segments.
authors.affiliation: Cardiology Division, Cardiac Arrhythmia Service, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA.
authors.forename: Jagdesh
authors.initials: J
authors.lastname: Kandala
authors.forename: Gaurav A
authors.initials: GA
authors.lastname: Upadhyay
authors.forename: Robert K
authors.initials: RK
authors.lastname: Altman
authors.forename: Abhishek
authors.initials: A
authors.lastname: Bose
authors.forename: E Kevin
authors.initials: EK
authors.lastname: Heist
authors.forename: Theofanie
authors.initials: T
authors.lastname: Mela
authors.forename: Jagmeet P
authors.initials: JP
authors.lastname: Singh
mesh_terms: D000368:Aged; D058406:Cardiac Resynchronization Therapy / Q000379:methods*; D004567:Electrodes, Implanted; D005260:Female; D006333:Heart Failure / Q000150:complications / Q000175:diagnosis* / Q000517:prevention & control; D006352:Heart Ventricles / Q000601:surgery*; D006801:Humans; D008297:Male; D019919:Prosthesis Implantation / Q000379:methods*; D016896:Treatment Outcome; D018487:Ventricular Dysfunction, Left / Q000150:complications / Q000175:diagnosis* / Q000517:prevention & control*