title: Effect of Cardiac Resynchronisation Therapy on Electrical Remodelling.
abstract: BACKGROUND
  Cardiac resynchronisation therapy (CRT) is an accepted device therapy in patients with low ejection fraction. Beneficial effects of CRT result from mechanical remodelling. Some controversial reports suggest that CRT may also induce electrical remodelling with intrinsic QRS narrowing but still the effect of CRT on electrical remodelling is an issue for debate. The aim of our study was to evaluate the effects of CRT on intrinsic QRS duration. For clarity, our analysis was performed by the signal averaged electrocardiogram (SAECG) which is a high resolution electrocardiographic signal suitable for accurate measurement of QRS duration. Signal averaged electrocardiogram provides a better value of QRS duration compared to 12-lead ECG by the ability to detect ventricular late potentials.
  
  
  METHODS
  A total of 48 consecutive patients with severe systolic dysfunction and typical left bundle branch block (LBBB) were enrolled in the study prospectively. Patients were scheduled for CRT-D implantation according to the current guidelines. Intrinsic QRS duration was accurately measured by SAECG before and at least 14 months after CRT implantation.
  
  
  RESULTS
  The mean intrinsic QRS duration remained unchanged during follow-up (from 149.9±13.8ms to 149.6±18.4ms; P= 0.3). Among 32 CRT responder patients, the mean intrinsic QRS duration remained unchanged during follow-up. Also, the mean intrinsic QRS duration showed no significant changes in 16 CRT non-responders.
  
  
  CONCLUSIONS
  Structural remodelling induced by CRT does not necessarily translate into decrease of intrinsic ventricular activation. Despite significant left ventricular recovery, electrical characteristics of the left ventricular conduction system cannot generally be expected to recuperate.
authors.affiliation: Shiraz University of Medical Sciences, Shiraz, Iran.
authors.forename: Amir
authors.initials: A
authors.lastname: Aslani
authors.affiliation: Shiraz University of Medical Sciences, Shiraz, Iran.
authors.forename: Mehrdad
authors.initials: M
authors.lastname: Khajei
authors.affiliation: Kowsar Hospital, Shiraz, Iran.
authors.forename: Shahab
authors.initials: S
authors.lastname: Shahrzad
authors.affiliation: Shiraz University of Medical Sciences, Shiraz, Iran.
authors.forename: Mohammad Hossein
authors.initials: MH
authors.lastname: Nikoo
authors.affiliation: Shiraz University of Medical Sciences, Shiraz, Iran.
authors.forename: Mohammad Vahid
authors.initials: MV
authors.lastname: Jorat
authors.affiliation: Shiraz University of Medical Sciences, Shiraz, Iran. Electronic address: draslani@yahoo.com.
authors.forename: Mohammad Ali Babaee
authors.initials: MA
authors.lastname: Bigi
mesh_terms: D002037:Bundle-Branch Block / Q000503:physiopathology / Q000628:therapy; D058406:Cardiac Resynchronization Therapy; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D011446:Prospective Studies; D013318:Stroke Volume; D020257:Ventricular Remodeling
keywords: Cardiac resynchronisation therapy; Intrinsic QRS duration; Signal averaged electrocardiogram