Po-01-181 delayed ventricular conduction alters ventricular repolarization in patients with heart failure: an electrocardiographic imaging study

In the normal human heart, the polarity of the T-wave is concordant with the QRS complex. This phenomenon is explained by longer repolarization of earlier activated regions. Patients with delayed ventricular conduction have discordant T-waves, but the link to regional repolarization is unknown. To compare epicardial repolarization-activation (RT-AT) relations in patients with heart failure and reduced ejection fraction (HFrEF) with those having a structural normal heart. 14 patients with HFrEF and delayed ventricular conduction and 11 patients no history of structural heart disease and a normal surface ECG (nQRS) were analyzed using ECG imaging (ECGI). HFrEF patients were categorized as left bundle branch block (LBBB, n=6) or non-specified intraventricular conduction disturbance (IVCD, n=8). ECGI was used to assess epicardial activation (ATs) and repolarization times (RTs). RT-AT relationships were evaluated for 24 segments using linear regression analysis. Interventricular repolarization dispersion (inter-RTD) was defined as the difference between average left-ventricular (LV) and right-ventricular RT, while total epicardial repolarization dispersion (total-RTD) was defined as the standard deviation of all epicardial RTs. The maximum of the local RT gradients (RTG) was defined as their 95th percentile. Kruskal Wallis tests were used to evaluate the differences between the groups. An HFrEF patient’s representative AT and RT bullseyes with a positive RT-AT relation (∼depolarize last, repolarize last) is provided in Figure1A. A positive RT-AT slope was present in the majority of HFrEF patients (1.14±0.17 for LBBB and 1.16±0.55 for IVCD), whereas the nQRS group (-0.25±2.16) demonstrated an overall slightly negative slope with high variability (Figure 1B and 1C). Individual (thin lines) and group-averaged (thick lines) RT-AT normalized slopes are visualized in Figure 1C. Both inter-RTD as well as total-RTD was significantly higher in the LBBB and IVCD group compared to the nQRS group, whereas RTG did not differ between the groups (Figure 1B). None of the RT parameters significantly differed between the LBBB and IVCD subgroup. This ECGI study shows that in patients with HFrEF, later activated regions also have a later completion of repolarization, regardless of conduction delay, whereas a variable RT-AT relation is present in subjects with structural normal hearts. HFrEF additionally initiates a higher degree of interventricular and total repolarization dispersion.