title: Time Course of Electrical Remodeling of Native Conduction After Cardiac Resynchronization Therapy and Its Impact on Clinical Outcome.
abstract: BACKGROUND
  Cardiac resynchronization therapy (CRT) induces structural and electrical remodeling (ER) in heart failure (HF) patients. Our aim was to assess time course of ER of native conduction and mechanical remodeling after CRT and impact of CRT-induced ER on clinical outcome.
  
  
  RESULTS
  We prospectively included 62 patients (aged 66 ± 10 years). Echocardiographic and ECG parameters were measured at baseline and 1, 3, 6, 9, and 12 months after implantation. Biventricular pacing was temporary inhibited during each follow-up to record intrinsic ECG. ER was defined as a decrease in native pre-implantation QRS duration ≥10 ms. During follow-up HF hospitalizations, cardiovascular death and transplantation (combined end point) were recorded. There were significant changes in intrinsic ECG parameters during follow-up; the narrowing of QRS duration was already observed after 1 month (median 185 ms [interquartile range (IQR) 175-194] vs 180 ms [170-194]; P < .001). Left ventricular (LV) volumes decreased only after 3 months of CRT (median end-systolic volume 167 mL [137-206] vs 140 mL [112-196]; P < .001). Only patients with ER (n = 24) exhibited significant mechanical remodeling and showed superior survival free from the combined end point compared with patients without ER (log-rank P = .028).
  
  
  CONCLUSIONS
  Electrical remodeling of native conduction precedes detectable left ventricular structural changes after CRT. ER of native conduction is associated with better clinical outcome following CRT.
authors.affiliation: Department of Cardiology, University Medical Center Ljubljana, Ljubljana, Slovenia. Electronic address: marta.cvijic@gmail.com.
authors.forename: Marta
authors.initials: M
authors.lastname: Cvijić
authors.affiliation: Department of Cardiology, University Medical Center Ljubljana, Ljubljana, Slovenia.
authors.forename: David
authors.initials: D
authors.lastname: Žižek
authors.affiliation: Department of Cardiology, University Medical Center Ljubljana, Ljubljana, Slovenia.
authors.forename: Bor
authors.initials: B
authors.lastname: Antolič
authors.affiliation: Department of Cardiology, University Medical Center Ljubljana, Ljubljana, Slovenia.
authors.forename: Igor
authors.initials: I
authors.lastname: Zupan
mesh_terms: D000368:Aged; D064752:Atrial Remodeling; D058406:Cardiac Resynchronization Therapy / Q000379:methods*; D004452:Echocardiography; D004562:Electrocardiography / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006329:Heart Conduction System / Q000503:physiopathology*; D006333:Heart Failure / Q000503:physiopathology / Q000628:therapy*; D006339:Heart Rate / Q000502:physiology; D006352:Heart Ventricles / Q000000981:diagnostic imaging / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D016896:Treatment Outcome; D020257:Ventricular Remodeling
keywords: Cardiac resynchronization therapy; electrical remodeling; native conduction