Transmural Repolarization Dispersion of Endocardial Biventricular Pacing Sites in Patients for Cardiac Resynchronization Therapy

Objectives: We sought to investigate the transmural repolarization dispersion (TRD) of endocardial biventricular pacing sites in patients for cardiac resynchronization therapy. Background: CRT reduces morbidity and mortality in patients with dyssynchronous LV failure; however epicardial pacing of LV and endocardial pacing of RV reverses the normal sequence of transmural repolarization and enhances TRD which facilitate fatal arrhythmia. Endocardial biventricular pacing yield natural transmural activation pattern and minimize TRD and reduce the incidence of ventricular arrhythmia. Methods: TRD was measured at precordial and limb leads at baseline and post pacing in CRT group (n=15), and in normal subjects (n=15). Endocardial biventricular pacing was performed at nine locations. Results: In CRT group, areas with enhanced TDR are RVapex-LVanterolateral (108 ± 19,68 ms, p<0.02), RVseptum-LVposterolateral (103±9ms, p<0.023), RVOTseptum-LVanterolateral (92 ± 19.12 ms), p<0.00), and RVOTseptum-LVposterolateral (105 ± 14,23 ms, p<0.001). In the control group, locations with increased TDR are RVapex-LV anteroateral (108 ± 19.60 ms, p<0.02), RVOTseptum-LVposterolateral (104 ± 13.35 ms, p<0.001), and RVOTseptum-LVanterolateral (92 ± 19.52 ms, p<0.000). Conclusions: CRT delivered at both LV and RV endocardial gives less transmural repolarization dispersion (TRD). The location of optimal TRD are RVapex-LVposterolateral, RVapex-LVlateral, RVseptum-LVanterolateral, RVseptum-LVlateral, and RVOTseptum-LVlateral.