title: Different regions of latest electrical activation during left bundle-branch block and right ventricular pacing in cardiac resynchronization therapy patients determined by coronary venous electro-anatomic mapping.
abstract: OBJECTIVE
  Current targeted left ventricular (LV) lead placement strategy is directed at the latest activated region during intrinsic activation. However, cardiac resynchronization therapy (CRT) is most commonly applied by simultaneous LV and right ventricular (RV) pacing without contribution from intrinsic conduction. Therefore, targeting the LV lead to the latest activated region during RV pacing might be more appropriate. We investigated the difference in LV electrical activation sequence between left bundle-branch block (LBBB) and RV apex (RVA) pacing using coronary venous electro-anatomic mapping (EAM).
  
  
  RESULTS
  Twenty consecutive CRT candidates with LBBB underwent intra-procedural coronary venous EAM during intrinsic activation and RVA pacing using EnSite NavX. Left ventricular lead placement was aimed at the latest activated region during LBBB according to current recommendations. In all patients, LBBB was associated with a circumferential LV activation pattern, whereas RVA pacing resulted in activation from the apex of the heart to the base. In 10 of 20 patients, RVA pacing shifted the latest activated region relative to LBBB. In 18 of 20 patients, the LV lead was successfully positioned in the latest activated region during LBBB. For the whole study population, LV lead electrical delay, expressed as percentage of QRS duration, was significantly shorter during RVA pacing than during LBBB (72 ± 13 vs. 82 ± 5%, P = 0.035).
  
  
  CONCLUSIONS
  Right ventricular apex pacing alters LV electrical activation pattern in CRT patients with LBBB, and shifts the latest activated region in a significant proportion of these patients. These findings warrant reconsideration of the current practice of LV lead targeting for CRT.
authors.affiliation: Maastricht University Medical Centre, Department of Cardiology, PO Box 5800, 6202 AZ, Maastricht, the Netherlands.
authors.forename: Masih
authors.initials: M
authors.lastname: Mafi Rad
authors.forename: Yuri
authors.initials: Y
authors.lastname: Blaauw
authors.forename: Trang
authors.initials: T
authors.lastname: Dinh
authors.forename: Laurent
authors.initials: L
authors.lastname: Pison
authors.forename: Harry J
authors.initials: HJ
authors.lastname: Crijns
authors.forename: Frits W
authors.initials: FW
authors.lastname: Prinzen
authors.forename: Kevin
authors.initials: K
authors.lastname: Vernooy
mesh_terms: D000368:Aged; D002037:Bundle-Branch Block / Q000503:physiopathology* / Q000628:therapy*; D058406:Cardiac Resynchronization Therapy; D003331:Coronary Vessels / Q000503:physiopathology*; D004452:Echocardiography; D004567:Electrodes, Implanted; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D011446:Prospective Studies; D018497:Ventricular Dysfunction, Right / Q000503:physiopathology* / Q000628:therapy*
keywords: Cardiac resynchronization therapy; Electro-anatomic mapping; Left bundle-branch block; Left ventricular electrical activation; Left ventricular lead placement; Right ventricular pacing