Left Bundle Branch Area Pacing: Anatomical and Physiological Features Made Easy

Figures

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  Figure 1. Demonstration of right and left interventricular septum with the porcine heart model. See also Video 1. (A) in situ view of the RV and RA septum. The triangle of Koch and the membranous septum are indicated by the white dashed line. The AV node is depicted in yellow. a is the proximal insertion site for LBBP. Entrapment in a cordal structure is shown. b is the midseptal insertion site for LFP. The absence of cordal structures in this zone is clearly recognizable. (B) View of the RV septum, with entanglement effect of the lead. (C) the right ventricular endocardium is dissected from the myocardium. This thin but stiff layer is responsible for the entanglement and barrier effect. (D) The LV septum, with an optimal subendocardial position of the lead helix is shown. Despite pressure on the lead, perforation does not occur due to a barrier effect. (E) Separation of the stiff left ventricular endocardial layer. The Tweezers are now in the LV subendocardial space, where the conduction system lies. (F) Perforation of the lead into the LV cavity occurs only after excessive pressure and lead rotations. RV, right ventricle; RA, right atrium; AV, atrioventricular; LBBAP, left bundle branch…

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  Figure 2. Macroscopic and X-ray anatomy correlation. (A) shows a porcine heart with a lateral wall incision of the right atrium and right ventricle, presenting the right atrial and ventricular septum from the right side. The dashed line delineates Koch’s triangle. The membranous septum is shown by transillumination from the left-sided subaortic position. The yellow pin indicates the position of the His bundle, and the red pin shows the basal insertion site for LBBAP. The lead is implanted into the middle septum, also known as the left bundle fascicular pacing side. (B) RAO X-ray projection of the patient during right ventricular angiography using the LBBAP sheath, which is in a slightly distal position. This view clearly demonstrates the entire right ventricular anatomy, including the trabeculation at the apical part, the right ventricle outflow tract (RVOT), and the tricuspid valve. The dashed line indicates the Koch’s triangle. The His bundle (bright yellow) runs anterior-superior, while the LBB (light yellow) tends to the ventricular apex after the bifurcation. (C) RAO X-ray projection of the patient during angiography of the right ventricle using the LBBAP sheath, in this case in a…

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  Figure 3. (A) Depiction of the conduction system using coloured cables. The traffic sign with construction works indicates a conduction block at different levels. The red dashed circle indicates the proximal left bundle branch site. The blue dashed circle indicates the mid-distal, fascicular level of the left bundle branch. The distal ends without isolation represent the Purkinje fibres. Once block occurs at the anatomical His level, but in predefined left bundle branch pathways, LBBB will occur. In such a scenario, stimulation of the His bundle distally to the block will effectively correct the block on the ECG. (B) The electrogram of LBB illustrates block at the anatomical LBB level (red dashed circle on figure A). (C) The electrogram of LBB illustrates LBB block-like ECG, without any blockade in the conduction system, but at the level of the LV endo-/myocardial tissue (blue dashed circle on the figure A). Panels B and C were modified from Tung R. et al. Arrhythm Electrophysiol Rev. 2020 with permission from Radcliffe Cardiology. RBB, right bundle branch; LBB, left bundle branch; PP, Purkinje Potential; H, his bundle potential; LB, left bundle potential; V, ventricular potential; A,…

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  Figure 4. Anatomy of the left bundle branch, the highway model. (A) Macroscopic image of immunoenzyme-labelling (dark brown signal) of neurofilament (NF-M) on the endocardial surface of the left ventricle of the rabbit. (B) The highway model. The left bundle branch (LBB) and its fascicles are presented as a highway, while regular myocardium is shown as the country road. The highway exits represent the Purkinje cells. Panel A was modified from Atkinson A. et al. Moll Cell Cardiol. 2011 with the permission of Elsevier Ltd. LBB, left bundle branch; LAF, left anterior fascicle; LSF, left septal fascicle; LPF, left posterior fascicle; CSP, conduction system pacing; LBBP, left bundle branch pacing; LBFP, left bundle fascicular pacing.

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  Figure 5. Correlation of cardiac anatomy and ECG for LBBAP. The left panel displays an anatomical cut (similar to a computer tomography view) of the human torso at the level of the Wilson ECG lead positions. On the right side, the combined ECG leads V1 and V6 demonstrate different types of capture. The stimulus captures the conduction system (bold green line) and/or myocardium (blue and red winding lines). The activation time is presented with corresponding coloured lines on the ECG. The V6-V1 interval is represented by pink colour. (A) ns-LBBP configuration, the conduction system and the LV septal myocardium are activated simultaneously. (B) s-LBBP—the capture occurs only in the conduction system. (C) LVSP scenario shows no capture of the conduction system, only the LV septal myocardium is activated. RV, right ventricle; LV, left ventricle; LBBP, left bundle branch pacing; Ns-LBBP, non-selective LBBP; s-LBBP, selective LBBP; LVSP, left ventricular septal pacing. The ECG images were modified from Jastrzebski M. et al. Europace 2021 with the courtesy of the Oxford University Press.