title: Endocardial left ventricular pacing improves cardiac resynchronization therapy in chronic asynchronous infarction and heart failure models.
abstract: BACKGROUND
  Studies in canine hearts with acute left bundle branch block (LBBB) showed that endocardial left ventricular (LV) pacing improves the efficacy of cardiac resynchronization therapy (CRT) compared with conventional epicardial LV pacing. The present study explores the efficacy of endocardial CRT in more compromised hearts and the mechanisms of such beneficial effects.
  
  
  RESULTS
  Measurements were performed in 22 dogs, 9 with acute LBBB, 7 with chronic LBBB combined with infarction (embolization; LBBB plus myocardial infarction, and concentric remodeling), and 6 with chronic LBBB and heart failure (rapid pacing, LBBB+HF, and eccentric remodeling). A head-to-head comparison was performed of the effects of endocardial and epicardial LV pacing at 8 sites. LV activation times were measured using ≈100 endocardial and epicardial electrodes and noncontact mapping. Pump function was assessed from right ventricular and LV pressures. Endocardial CRT resulted in better electric resynchronization than epicardial CRT in all models, although the benefit was larger in concentrically remodeled LBBB plus myocardial infarction than in eccentrically remodeled LBBB+HF hearts (19% versus 10%). In LBBB and LBBB+HF animals, endocardial conduction was ≈50% faster than epicardial conduction; in all models, transmural impulse conduction was ≈25% faster when pacing from the endocardium than from the epicardium. Hemodynamic effects were congruent with electric effects.
  
  
  CONCLUSIONS
  Endocardial CRT improves electric synchrony of activation and LV pump function compared with conventional epicardial CRT in compromised canine LBBB hearts. This benefit can be explained by a shorter path length along the endocardium and by faster circumferential and transmural impulse conduction during endocardial LV pacing.
authors: Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, Limburg, The Netherlands.
authors: Marc
authors: M
authors: Strik
authors: Leonard M
authors: LM
authors: Rademakers
authors: Caroline J M
authors: CJ
authors: van Deursen
authors: Arne
authors: A
authors: van Hunnik
authors: Marion
authors: M
authors: Kuiper
authors: Catherine
authors: C
authors: Klersy
authors: Angelo
authors: A
authors: Auricchio
authors: Frits W
authors: FW
authors: Prinzen
mesh_terms: D000818:Animals; D002304:Cardiac Pacing, Artificial; D058406:Cardiac Resynchronization Therapy / Q000379:methods*; D002908:Chronic Disease; D004195:Disease Models, Animal; D004285:Dogs; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D006333:Heart Failure / Q000150:complications / Q000503:physiopathology / Q000628:therapy*; D008297:Male; D009203:Myocardial Infarction / Q000150:complications / Q000503:physiopathology / Q000628:therapy*; D016896:Treatment Outcome