title: Identifying delayed left ventricular lateral wall activation in patients with non-specific intraventricular conduction delay using coronary venous electroanatomical mapping.
abstract: BACKGROUND
  Delayed left ventricular (LV) lateral wall activation is considered the electrical substrate that characterises patients suitable for cardiac resynchronisation therapy (CRT). Although typically associated with left bundle branch block, delayed LV lateral wall activation may also be present in patients with non-specific intraventricular conduction delay (IVCD). We assessed LV lateral wall activation in a cohort of CRT candidates with IVCD using coronary venous electroanatomical mapping, and investigated whether baseline QRS characteristics on the ECG can identify delayed LV lateral wall activation in this group of patients.
  
  
  METHODS
  Twenty-three consecutive CRT candidates with IVCD underwent intra-procedural coronary venous electroanatomical mapping using EnSite NavX. Electrical activation time was measured in milliseconds from QRS onset and expressed as percentage of QRS duration. LV lateral wall activation was considered delayed if maximal activation time measured at the LV lateral wall (LVLW-AT) exceeded 75 % of the QRS duration. QRS morphology, duration, fragmentation, axis deviation, and left anterior/posterior fascicular block were assessed on baseline ECGs.
  
  
  RESULTS
  Delayed LV lateral wall activation occurred in 12/23 patients (maximal LVLW-AT = 133 ± 20 ms [83 ± 5 % of QRS duration]). In these patients, the latest activated region was consistently located on the basal lateral wall. QRS duration, and prevalence of QRS fragmentation and left/right axis deviation, and left anterior/posterior fascicular block did not differ between patients with and without delayed LV lateral wall activation.
  
  
  CONCLUSIONS
  Coronary venous electroanatomical mapping can be used at the time of CRT implantation to determine the presence of delayed LV lateral wall activation in patients with IVCD. QRS characteristics on the ECG seem unable to identify delayed LV lateral wall activation in this subgroup of patients.
authors.affiliation: Department of Cardiology, Maastricht University Medical Center, PO Box 5800, 6202AZ, Maastricht, The Netherlands.
authors.forename: A M W
authors.initials: AM
authors.lastname: van Stipdonk
authors.affiliation: Department of Cardiology, Maastricht University Medical Center, PO Box 5800, 6202AZ, Maastricht, The Netherlands.
authors.forename: M Mafi
authors.initials: MM
authors.lastname: Rad
authors.affiliation: Department of Cardiology, Maastricht University Medical Center, PO Box 5800, 6202AZ, Maastricht, The Netherlands.
authors.forename: J G L M
authors.initials: JG
authors.lastname: Luermans
authors.affiliation: Department of Cardiology, Maastricht University Medical Center, PO Box 5800, 6202AZ, Maastricht, The Netherlands.
authors.forename: H J
authors.initials: HJ
authors.lastname: Crijns
authors.affiliation: Department of Physiology, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, Maastricht, The Netherlands.
authors.forename: F W
authors.initials: FW
authors.lastname: Prinzen
authors.affiliation: Department of Cardiology, Maastricht University Medical Center, PO Box 5800, 6202AZ, Maastricht, The Netherlands. kevin.vernooy@mumc.nl.
authors.forename: K
authors.initials: K
authors.lastname: Vernooy
keywords: Cardiac resynchronisation therapy; Coronary venous electroanatomical mapping; Non-specific intraventricular conduction delay; QRS characteristics