Tailoring device settings in cardiac resynchronization therapy using electrograms from pacing electrodes

Aims Left ventricular (LV) fusion pacing appears to be at least as beneficial as biventricular pacing in cardiac resynchronization therapy (CRT). Optimal LV fusion pacing critically requires adjusting the atrioventricular (AV)-delay to the delay between atrial pacing and intrinsic right ventricular (RV) activation (Ap-RV). We explored the use of electrogram (EGM)-based vectorloop (EGMV) derived from EGMs of implanted pacing leads to achieve optimal LV fusion pacing and to compare it with conventional approaches. Methods and results During CRT-device implantation, 28 patients were prospectively studied. During atrial-LV pacing (Ap-LVp) at various AV-delays, LV dP/dt(max), 12-lead electrocardiogram (ECG), and unipolar EGMs were recorded. Electrocardiogram and electrogram were used to reconstruct a vectorcardiogram (VCG) and EGMV, respectively, from which the maximum QRS amplitude (QRS(ampl)), was extracted. Ap-RV was determined: (i) conventionally as the longest AV-delay at which QRS morphology was visually unaltered during RV pacing at increasing AV-delays( Ap-RVvis; reference-method); (ii) 70% of delay between atrial pacing and RV sensing (Ap-RVaCRT); and (iii) the delay between atrial pacing and onset of QRS (Ap-QRS(onset)). In both the EGMV and VCG, the longest AV-delay showing an unaltered QRS(ampl) as compared with Ap-LVp with a short AV-delay, corresponded to Ap-RVvis. In contrast, Ap-QRS(onset) and Ap-RVaCRT were larger. The Ap-LVp induced increase in LV dP/dt(max) was larger at Ap-RVvis, Ap-RVEGMV, and Ap-RVVCG than at Ap-QRS(onset) (all P < 0.05) and Ap-RVaCRT (P = 0.02, P = 0.13, and P = 0.03, respectively). Conclusion In this acute study, it is shown that the EGMV QRSampl can be used to determine optimal and individual CRT-device settings for LV fusion pacing, possibly improving long-term CRT response.