Right Bundle Branch Conduction in Left Bundle Branch Area Pacing

Figures

• 

  FIGURE 1. Chest leads of a 12‐lead electrocardiogram during implantation (A, C, D) and fluoroscopic image (B) in Case 1. (A) Intrinsic rhythm with 2:1 AVB and RBBB. QRSd was 178 ms. (B) Fluoroscopic RAO 30° view (top) and LAO 60° view (bottom) during implantation. (C) NS‐LBBP. Stim‐V6RWPT was 70 ms and Stim‐V1RWPT was 100 ms. (D) S‐LBBP. Stim‐V6RWPT was 70 ms, Stim‐V1RWPT was 114 ms, and a discrete potential after the pacing stimulus was observed in the endocardial EGM. AVB, atrioventricular block; EGM, electrogram; LAO, left anterior oblique; NS‐LBBP, nonselective left bundle branch pacing; RAO, right anterior oblique; RBBB, right bundle branch block; S‐LBBP, selective left bundle branch pacing; Stim‐V1RWPT, interval between stimulus artifact and peak of the R wave in lead V1; Stim‐V6RWPT, interval between stimulus artifact and peak of the R wave in lead V6; QRSd, QRS duration.

• 

  FIGURE 2. Chest leads of a 12‐lead electrocardiogram during implantation (A, C–F), fluoroscopic image (B) and chest leads of a 12‐lead electrocardiogram on the day after implantation (G) in Case 2. (A) Intrinsic rhythm with no conduction disturbance and a narrow QRS morphology. QRSd was 80 ms. (B) Fluoroscopic RAO 30° view (top) and LAO 60° view (bottom) during implantation. (C) Presumed peripheral RBBB associated with mechanical injury to the RBB related to the delivery catheter. QRSd was 140 ms. (D) NS‐LBBP with anodal capture in the presence of peripheral RBBB. Stim‐V6RWPT was 70 ms, Stim‐V1RWPT was 89 ms and Stim‐V1R'WPT was 132 ms. (E) NS‐LBBP in the presence of peripheral RBBB. Stim‐V6RWPT was 70 ms, Stim‐V1RWPT was 110 ms and Stim‐V1R'WPT was 132 ms. (F) S‐LBBP in the presence of peripheral RBBB. Stim‐V6RWPT was 70 ms, Stim‐V1RWPT was 110 ms and Stim‐V1R'WPT was 144 ms. (G) LBBAP after recovery of RBB conduction. LBBAP, left bundle branch area pacing; RBB, right bundle branch; Stim‐V1R'WPT, interval between stimulus artifact and peak of the R′ wave in lead V1. Other abbreviations as in Figure 1.

• 

  FIGURE 3. A schematic illustrating the mechanism of electrical activation penetrating the RBB in LBBAP. The yellow arrows indicate LBB conduction, the green arrows indicate RBB conduction, and the red arrows indicate myocardial conduction. (A) Direct anodal capture of the RBB by the ring electrode. (B) Conduction from the LBB to the RBB through a transverse interconnection between them. (C) Conduction from the septal branches of the LBB to the septal myocardium, with subsequent penetration into the RBB via its septal branches. (D) Penetration from the LV septal myocardium into the RBB via its septal branches. (E) Penetration from the LV septal myocardium into the LBB via its septal branches and subsequent conduction to the RBB through a transverse interconnection between the LBB and RBB. LBB, left bundle branch; LV, left ventricular. Other abbreviations as in Figures 1 and 2.

• 

  FIGURE 4. The estimated pattern of electrical activation in Case 1 (A–C) and Case 2 (D–J). The yellow arrows indicate LBB conduction, the green arrows indicate RBB conduction, and the red arrows indicate myocardial conduction. (A) Intrinsic rhythm with central RBBB. (B) NS‐LBBP in the presence of central RBBB. (C) S‐LBBP in the presence of central RBBB. (D) Intrinsic rhythm with no conduction disturbance and a narrow QRS morphology. (E) Presumed peripheral RBBB associated with mechanical injury to the RBB related to the delivery catheter. (F) NS‐LBBP with anodal capture in the presence of peripheral RBBB. (G) NS‐LBBP in the presence of peripheral RBBB. (H) S‐LBBP in the presence of peripheral RBBB. (I) NS‐LBBP after recovery of RBB conduction. (J) S‐LBBP after recovery of RBB conduction. Abbreviations as in Figures 1 and 2.