Significant Delayed Activation on the Right Ventricular Outflow Tract Represents Complete Right Bundle‐Branch Block Pattern in Brugada Syndrome

Figure 1. Body surface mapping system and interpretation of the body surface locations and divided areas of the ventricles. A, Locations of electrodes in the 87‐lead body surface mapping system (BSM). A–I are placed on the anterior chest, and J–M are located on the back. E is located at the median line of the anterior chest. A and I are located at the right and left midaxillary lines, respectively. Row 6 is placed at the level of the parasternal second intercostal space, and row 4 is placed at the midclavicular 5th intercostal space. Row 5 is placed between rows 6 and 4, and rows 7, 3, 2, and 1 are located vertically at equal intervals. Leads V1–V3 are positioned at crosses (X), and leads V4–6 are coincident with G4, H4, and I4, respectively. Adapted from Morita et al 17 with permission. Copyright © 2008, Heart Rhythm Society. B, Isochronal map of ventricular activation time based on BSM (control group Case 5). Color bar at the right side of the map shows activation time from the onset of the QRS complex. Blue color shows an early activation area, and red color shows a late activation area. For statistical analysis, we divided the anterior 59 leads into 4 regions (inferior and lateral RV…

Figure 2. Comparison of the QRS interval, QTc interval on 12‐lead ECG, and HV interval between the Brugada syndrome and the control groups. QRS interval was significantly longer in the Brugada syndrome (BrS) group than that in the control group (A). There was no significant difference in QTc interval between the BrS group and the control group (B). HV interval tended to be longer in the BrS group than in the control group, but the difference was not significant (C).

Figure 3. Interpretation of the ventricular activation time map. A, The ventricular activation map of Case 1 in the control patients. Dark blue and green area represents early activation site. Yellow to orange area shows late activation site. Arrows show propagation of excitation, and zig‐zag lines represent conduction delay. Excitation occurs from posterior left ventricle (LV) and anterior LV; those could represent excitations from posterior and anterior fascicles. Excitation propagated to right ventricle (RV) with conduction delay at the intraventricular septum. B, Ventricular activation map of Case 5 in the Brugada syndrome group. Excitations occur from LV and propagate to inferior site of RV, then propagated to RV outflow tract (RVOT) with significant conduction delay. IVS indicates intraventricular septum.

Figure 4. Ventricular activation time map in the control group. Isochronal maps of ventricular activation time in control cases (Cases 1–8). Right ventricular (RV) activation occurred via transeptal spread toward the right ventricular outflow tract with delayed conduction in the entire RV in all patients. Black dot square shows inferolateral RV, blue dot square shows RVOT and mild RV, brown dot square shows intraventricular septum, and yellow dot square shows left ventricle. IVS indicates intraventricular septum; LV, left ventricle; and RVOT, right ventricular outflow tract.

Figure 5. Ventricular activation time map in the Brugada syndrome group. Isochronal maps of ventricular activation time in patients with Brugada syndrome (BrS) (Cases 1–11). There were 7 patients in the BrS group without the proximal right bundle‐branch block pattern (Cases 1–7). The right ventricular (RV) activation propagated from the inferior and lateral RV toward the right ventricular outflow tract with significant activation delay. The other 4 patients (Cases 8–11) in the BrS group exhibited the RV activation pattern similar to that in the control group. Black dot square shows inferolateral RV, blue dot square shows RVOT and mild RV, brown dot square shows intraventricular septum, and yellow dot square shows left ventricle. IVS indicates intraventricular septum; LV, left ventricle; and RVOT, right ventricular outflow tract.

Figure 6. Average ventricular activation time map in each group. We calculated the mean ventricular activation times of each unipolar lead in the control group, overall Brugada syndrome (BrS) group, BrS group without the proximal right bundle‐branch block (RBBB) pattern, and BrS group with the proximal RBBB pattern. Then we created an isochronal map to evaluate the difference in the right ventricular (RV) activation pattern among these groups. A, Control group. B, BrS group (overall). C, BrS group with different RV activation pattern (Cases 1–7). D, BrS group with proximal RBBB pattern (Cases 8–11). In contrast to the control group, RV activation propagated faster in the inferior‐lateral RV visually in the BrS group. This difference in RV activation was more obvious in the BrS group without the proximal RBBB pattern. In the BrS group with the proximal RBBB pattern, the entire RV activation was more delayed compared with that in the control group. Black dot square shows inferolateral RV, blue dot square shows RVOT and mild RV, brown dot square shows intraventricular septum, and yellow dot square shows left ventricle. IVS indicates intraventricular septum; LV, left ventricle; RV, right…

Figure 7. Comparisons of log‐transformed ventricular activation time in each divided area of anterior ventricle between the Brugada syndrome and the control groups. A, Log‐transformed ventricular activation time (VAT) in overall Brugada syndrome (BrS) patients, Patients with BrS without proximal right bundle‐branch block (RBBB) and control. B, VAT in inferior and lateral right ventricle (RV). There was no significant difference in VAT between the overall BrS group and the control group. VAT at the inferior and lateral RV in the BrS group without the proximal RBBB pattern was significantly shorter than that in the control group. VAT right ventricular outflow tract and mid RV (C), intraventricular septum (D), and left ventricle (E) were not different between overall BrS patients and control group, and between BrS without proximal RBBB and control.

Figure 8. Comparisons of the latest ventricular activation time in each divided area of ventricle between the Brugada syndrome and the control groups. Comparison of the latest ventricular activation time (VAT) in each area (A), inferior and lateral right ventricle (RV), (B), right ventricular outflow tract (RVOT) and mid RV, (C), intraventricular septum, and (D), left ventricle. The latest VAT in the RVOT and mid RV in the Brugada syndrome (BrS) group was significantly longer than that in the control group. The latest VATs in other area in the BrS were not significantly different.

Figure 9. Ventricular activation time maps before and after development of complete right bundle‐branch block in Brugada syndrome group Case 2. The maps show isochronal maps of ventricular activation time before (A) and after (B) development of complete right bundle‐branch block (CRBBB) in Brugada syndrome Case 2. The area of significant delayed conduction was larger after CRBBB than before CRBBB. However, activation in the inferolateral region in the right ventricle did not seem to be different before and after CRBBB (C). Black dot square shows inferolateral RV, blue dot square shows RVOT and mild RV, brown dot square shows intraventricular septum, and yellow dot square shows left ventricle. IVS indicates intraventricular septum; LV, left ventricle; RV, right ventricle; and RVOT, right ventricular outflow tract.

Figure 10. Average QTc interval map in each group. A, Control group. B, Brugada syndrome (BrS) group (overall). C, BrS group without proximal right bundle‐branch block (RBBB) pattern (Cases 1–7). D, BrS group with proximal RBBB pattern (Cases 8–11). Longer QTc interval was observed in right ventricular outflow tract (RVOT), mid RV and septum, and shorter QTc interval was observed in inferolateral RV and posterior left ventricle (LV) in both the BrS and control groups. There was no QTc interval heterogeneity within RVOT area in both of the groups. There was no obvious QTc interval distribution between the BrS group with and without proximal RBBB. Black dot square shows inferolateral RV, blue dot square shows RVOT and mild RV, brown dot square shows intraventricular septum, and yellow dot square shows left ventricle. IVS indicates intraventricular septum; and RV, right ventricle.

Figure 11. Comparison of QRS morphologies in anterior inferior unipolar leads in each group. Investigation of whether 4 unipolar leads (C1‐2, D1‐2) presented with rsR’, rSR’, or rR’ morphology. The red circle indicates typical complete right bundle‐branch block (CRBBB) morphology, and the blue circle indicates atypical CRBBB morphology. (A) 4/4 unipolar leads presented with typical CRBBB morphology, as was observed in many cases in the control group (control Case 1). (B) 0/4 unipolar leads presented with typical CRBBB morphology in the Brugada syndrome (BrS) group without the proximal right bundle‐branch block (RBBB) pattern (BrS Case 5). (C) 4/4 unipolar leads presented with typical CRBBB morphology in the BrS group with the proximal RBBB pattern (BrS Case 10). IVS indicates intraventricular septum; LV, left ventricle; RV, right ventricle; and RVOT, right ventricular outflow tract.