Evidence of reverse electrical remodelling by non-invasive electrocardiographic imaging to assess acute and chronic changes in bulk ventricular activation following cardiac resynchronisation therapy.

INTRODUCTION: Cardiac resynchronisation therapy (CRT) corrects electrical dyssynchrony. However, the temporal changes in the electrical timing according to substrate are unclear. We used electrocardiographic imaging (ECGi) for serial non-invasive assessment of the underlying electrical substrate and its response to resynchronisation. MATERIAL AND METHODS: ECGi activation maps were constructed 1 day and 6 months post CRT implant. ECGi maps were analysed offline to determine the total ventricular activation time (TVaT) and the time for the bulk of ventricular activation (10th to 90th percentile activation; VaT10-90 Index). Statistical analysis was performed using repeated measures ANOVA with post-hoc pairwise comparisons using paired t-tests. The % relative change within each time point was also calculated and compared between the two time points. RESULTS: Eleven CRT patients were studied. Both total and bulk ventricular activation significantly decreased with CRT turned ON at day 1. Intrinsic (CRT OFF) TVaT and VaT10-90 Index at day 1 were 143 ± 23 and 84 ± 20 ms, respectively, and they significantly decreased post CRT to 115 ± 26 ms (P < 0.001) and 49 ± 17 ms (P < 0.05), respectively. The relative change at day 1 was also statistically significant for TVaT (19 ± 12%, P < 0.001) and VaT10-90 Index (39 ± 25%, P < 0.001). After 6 months, the relative decrease in TVaT with CRT ON remained stable (19% vs. 18% at day 1 and 6 months, respectively) whereas reduction the in VaT10-90 Index was decreased 39% vs. 26% at day 1 and 6 months, respectively. In non-ischaemic patients both total and bulk activation times reduced following CRT. Volumetric responders exhibited an electrical remodelling for bulk activation not apparent in Non-responders, after 6 months of CRT ON. CONCLUSIONS: Intrinsic bulk myocardium activation becomes more rapid and synchronous with CRT. The bulk activation time is more susceptible to improvement by CRT in ischaemic patients and volumetric responders. These observations are consistent with CRT causing reverse electrophysiological remodelling in the bulk myocardium, but not in late-activating ischaemic or fibrotic regions.

Non-invasive electrophysiological assessment of the optimal configuration of quadripolar lead vectors on ventricular activation times.

BACKGROUND: Cardiac resynchronization therapy (CRT) is now generally delivered via quadripolar leads. Assessment of the effect of different vector programs from quadripolar leads on ventricular activation can be now done using non-invasive electrocardiographic mapping (ECM). MATERIAL AND METHODS: In nineteen patients with quadripolar LV leads, activation maps were constructed. The total ventricular activation time (TVaT) and the time for the bulk of ventricular activation (VaT10-90) were calculated. RESULTS: CRT delivered via a quadripolar lead significantly reduced TVaT and VaT10-90 by a mean of 16 ms and 31 ms, respectively, compared to baseline. There was a marked reduction in ventricular activation between the most and least synchronous vectors: 28% difference in baseline TVaT and 37% difference in VaT10-90. CONCLUSION: Changes in the configuration of an LV quadripolar lead significantly affected ventricular activation timings in both ischaemic and non-ischaemic subjects. This suggests that programming of the optimal pacing vector may need to be individually tailored.

Comparison of Echocardiographic and Electrocardiographic Mapping for Cardiac Resynchronisation Therapy Optimisation.

STUDY HYPOTHESIS: We sought to investigate the association between echocardiographic optimisation and ventricular activation time in cardiac resynchronisation therapy (CRT) patients, obtained through the use of electrocardiographic mapping (ECM). We hypothesised that echocardiographic optimisation of the pacing delay between the atrial and ventricular leads-atrioventricular delay (AVD)-and the delay between ventricular leads-interventricular pacing interval (VVD)-would correlate with reductions in ventricular activation time. BACKGROUND: Optimisation of AVD and VVD may improve CRT patient outcome. Optimal delays are currently set based on echocardiographic indices; however, acute studies have found that reductions in bulk ventricular activation time correlate with improvements in acute haemodynamic performance. MATERIALS AND METHODS: Twenty-one patients with established CRT criteria were recruited. After implantation, patients underwent echo-guided optimisation of the AVD and VVD. During this procedure, the participants also underwent noninvasive ECM. ECM maps were constructed for each AVD and VVD. ECM maps were analysed offline. Total ventricular activation time (TVaT) and a ventricular activation time index (VaT10-90) were calculated to identify the optimal AVD and VVD timings that gave the minimal TVaT and VaT10-90 values. We correlated cardiac output with these electrical timings. RESULTS: Echocardiographic programming optimisation was not associated with the greatest reductions in biventricular activation time (VaT10-90 and TVaT). Instead, bulk activation times were reduced by a further 20% when optimised with ECM. A significant inverse correlation was identified between reductions in bulk ventricular activation time and improvements in LVOT VTI (p < 0.001), suggesting that improved ventricular haemodynamics are a sequelae of more rapid ventricular activation. CONCLUSIONS: EAM-guided programming optimisation may achieve superior fusion of activation wave fronts leading to improvements in CRT response.

Erratum to "Comparison of Echocardiographic and Electrocardiographic Mapping for Cardiac Resynchronisation Therapy Optimisation".

[This corrects the article DOI: 10.1155/2019/4351693.].