title: Comparison of the Effects of Epicardial and Endocardial Cardiac Resynchronization Therapy on Transmural Dispersion of Repolarization.
abstract: BACKGROUND
  Despite significant improvements in cardiac output and functional capacity with cardiac resynchronization therapy (CRT), incidence of sudden cardiac death still remains high. Reversal of physiological myocardial activation sequence during epicardial pacing increases the transmural dispersion of repolarization (TDR). The aim of this study was to compare the effects of endocardial and epicardial biventricular pacing on repolarization parameters in the same patient group.
  
  
  METHODS
  Seven patients who had transseptal endocardial left ventricle (LV) lead placement, in whom epicardial CRT had failed due to coronary sinus (CS) lead dislodgement after successful implantation, were admitted to the study. LV endocardial leads were implanted through the interatrial septum in a lateral position. Electrocardiograms (ECGs) were scanned before and after successful epicardial and endocardial biventricular pacing and analyzed using digital calipers. ECG markers of TDR (TpTe and TpTe/QT ratio) were measured and compared.
  
  
  RESULTS
  Baseline QRS durations (161.7 ± 15.9 ms vs 162.2 ± 17.8 ms, P = 0.95), TpTe values (107.1 ± 20.5 ms vs 108.5 ± 17.6 ms, P = 0.89), and TpTe/QT ratios (0.24 ± 0.05 vs 0.24 ± 0.03, P = 0.88) were similar before epicardial and endocardial CRT. QRS interval reduction was similar (-28.3 ± 11.6 ms vs -29.1 ± 11.4 ms, P = 0.89) in both groups. Compared to transseptal endocardial CRT, epicardial CRT was associated with a significant increase in TpTe (17.1 ± 19.5 ms vs -12.6 ± 18.9 ms, P = 0.01) and TpTe/QT ratio (0.03 ± 0.04 vs -0.02 ± 0.03, P = 0.04).
  
  
  CONCLUSIONS
  Transseptal LV endocardial pacing is associated with significant reduction in TDR characteristics compared to epicardial pacing in CRT. Further studies are warranted to determine whether these effects may contribute to reduction of arrhythmias in patients with CRT.
authors.affiliation: Heart Center, Semmelweis University, Budapest, Hungary.
authors.forename: Emin Evren
authors.initials: EE
authors.lastname: Özcan
authors.affiliation: Heart Center, Semmelweis University, Budapest, Hungary.
authors.forename: Szabolcs
authors.initials: S
authors.lastname: Szilagyi
authors.affiliation: Heart Center, Semmelweis University, Budapest, Hungary.
authors.forename: Zoltan
authors.initials: Z
authors.lastname: Sallo
authors.affiliation: Heart Center, Semmelweis University, Budapest, Hungary.
authors.forename: Levente
authors.initials: L
authors.lastname: Molnar
authors.affiliation: Heart Center, Semmelweis University, Budapest, Hungary.
authors.forename: Endre
authors.initials: E
authors.lastname: Zima
authors.affiliation: Heart Center, Semmelweis University, Budapest, Hungary.
authors.forename: Gabor
authors.initials: G
authors.lastname: Szeplaki
authors.affiliation: Heart Center, Semmelweis University, Budapest, Hungary.
authors.forename: Istvan
authors.initials: I
authors.lastname: Osztheimer
authors.affiliation: Department of Cardiology, Sifa University, Izmir, Turkey.
authors.forename: Ali
authors.initials: A
authors.lastname: Öztürk
authors.affiliation: Heart Center, Semmelweis University, Budapest, Hungary.
authors.forename: Béla
authors.initials: B
authors.lastname: Merkely
authors.affiliation: Heart Center, Semmelweis University, Budapest, Hungary.
authors.forename: Laszlo
authors.initials: L
authors.lastname: Geller
mesh_terms: D058406:Cardiac Resynchronization Therapy / Q000379:methods*; D004699:Endocardium / Q000503:physiopathology*; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006333:Heart Failure / Q000503:physiopathology* / Q000517:prevention & control*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010496:Pericardium / Q000503:physiopathology*; D016896:Treatment Outcome
keywords: cardiac resynchronization therapy; heart failure; transmural dispersion of repolarization; transseptal endocardial biventricular pacing; ventricular arrhythmias