The influence of delayed ventricular activation on cardiac repolarization: Insights from electrocardiographic imaging

Figures

• 

  Figure 1. Reconstruction of epicardial unipolar electrograms A, an example of an activation map of a patient with an IVCD. B, reconstructed epicaridal unipolar electrograms at specific locations in the same activation map. Indicated are the AT (red caliber) and RT (blue caliber). IVCD, intraventricular conduction disturbance; AT, activation time.

• 

  Figure 2. Example patients: surface ECG and ECGi results A, selection of leads of the standard 12‐lead ECGs from example patients with a nQRS, an IVCD and a LBBB. B, 24‐segment bullseye plot of the activation time and repolarization time in the same patients. Activation and repolarization times are defined as the interval between onset of QRS on the body surface and the steepest epicardial downslope of the QRS complex and upslope of the T‐wave respectively. nQRS, narrow QRS; IVCD, intraventricular conduction disturbance; LBBB, left bundle branch; ECGi, electrocardiographic imaging.

• 

  Figure 3. Example patients: Activation and Repolarization time distribution and relationship A, distribution of activation and repolarization times in the left ventricle (red) and right ventricle (green) over a cardiac cycle for the same patients as in Fig. 2. Upper: timing of activation and repolarization relative to lead V3 of the standard 12‐lead ECG. Lower: number of nodes with a specific activation or repolarization time in the same beat as the upper panel. B, activation–repolarization relationship for these patients. Each dot represents the mean activation and repolarization in a segment. The line is a first‐degree polynomial, fitted by linear regression. nQRS, narrow QRS; IVCD, intraventricular conduction disturbance; LBBB, left bundle branch block; LV, left ventricle; RV, right ventricle; ECGi, electrocardiographic imaging.

• 

  Figure 4. AT‐RT Relationship The AT‐RT relationship for nQRS, IVCD and LBBB patients. The dots are the mean AT and mean RT in each group. The line represents the mean slope and runs from the minimal AT to the maximal AT. The areas represent the mean ± SD of the slope. nQRS, narrow QRS; IVCD, intraventricular conduction disturbance; LBBB, left bundle branch block; LV, left ventricle; RV, right ventricle.

• 

  Figure 5. Activation and Repolarization Parameters Scatter plots of the ECGi parameters. Each ring represents a patient. nQRS, IVCD and LBBB are depicted in green, blue and red respectively. The horizontal black lines represent median values. *Significant difference between the LV and RV within a group (e.g. nQRS LV vs. nQRS RV), as determined by the Wilcoxon signed‐rank test. #Significant difference compared to the nQRS group (e.g. nQRS vs. IVCD; both including LV and RV) using the Kruskal–Wallis test followed by multiple comparison. nQRS, narrow QRS; IVCD, intraventricular conduction disturbance; LBBB, left bundle branch block; LV, left ventricle; RV, right ventricle; AT, activation time; RT, repolarization time; VEU, ventricular electrical uncoupling; SDAT, standard deviation of activation time; SDRT, standard deviation of repolarization time.

• 

  Figure 6. AT‐VEU and RT‐VEU relationship The AT‐VEU and RT‐VEU relationship in nQRS patients (green) and broad QRS patients (black). Each dot represents a patient. The VEU is defined as the difference between mean AT or RT of the LV and RV. r indicates the Pearson correlation coefficient and the P value indicates the significance of this coefficient and thereby the existence of a relationship between AT‐VEU and RT‐VEU. nQRS, narrow QRS; LV, left ventricle; RV, right ventricle; VEU, ventricular electrical uncoupling.