Abstract 3787: Three-Dimensional Electrical Mapping During Endocardial and Epicardial Cardiac Resynchronization Therapy
Introduction: We previously demonstrated that endocardial (ENDO) left ventricular (LV) pacing for cardiac resynchronization therapy improves LV pump function compared to conventional epicardial (EPI) LV pacing in a left bundle branch block (LBBB) model. We performed 3D mapping studies to investigate electrical asynchrony during ENDO versus EPI biventricular pacing (BiVP).
Methods: In 6 anesthetized dogs with experimental LBBB, simultaneous pacing was performed at RV apex and 8 paired LV sites (ENDO and EPI). Asynchrony was expressed as activation time (AT). Non-contact mapping (EnSite®) was used to determine LV ENDO-AT and EPI contact mapping to determine LV EPI-AT (61 LV EPI and RV septum electrodes). Total AT (TAT) was calculated as largest activation delay between all LV and 51 RV EPI electrodes. LV pump function was assessed as LV dP/dTmax.
Results: For all measurements during baseline LBBB, EPI-BiVP and ENDO-BiVP, respectively, TAT was 93±6, 85±9* and 73±9 ms*# (*=p <0.01 compared to LBBB, #=p<0.01 compared between ENDO- and EPI-BiVP); LV EPI-AT was 90±5, 83±9 ms* and 63±13 ms*#, and LV ENDO-AT was 36±8; 36±10 ms and 64±14 ms*#. The figure⇓ shows that ENDO-BiVP shortens TAT and EPI-AT due to faster transmural conduction, while EPI-BiVP shortens LV ENDO-AT due to wider endocardial breakthrough. The activation times are also depicted in the time bars. ENDO-BiVP resulted in a significantly larger LV dP/dTmax improvement than EPI-BiVP (21±9 %*# versus 16±8 %* above LBBB).
Conclusion: Compared to baseline LBBB and EPI-BiV pacing, ENDO-BiV pacing improves LV pump function due to a large reduction in LV EPI- and total AT. ENDO-AT is not an important determinant of TAT and of pump function.