Anatomy of the cardiac conduction system

Abstract

The specialized cardiomyocytes that constitute the conduction system in the human heart, initiate the electric impulse and result in rhythmic and synchronized contraction of the atria and ventricles. Although the atrioventricular (AV) conduction axis was described more than a century ago by Sunao Tawara, the anatomic pathway for propagation of impulse from atria to the ventricles has been a topic of debate for years. Over the past 2 decades, there has been a resurgence of conduction system pacing (CSP) by implanting pacing leads in the His bundle region in lieu of chronic right ventricular pacing that is associated with worse clinical outcomes. The inherent limitations of implanting the leads in the His bundle region has led to the emergence of left bundle branch area pacing in the past 3 years as an alternative strategy for CSP. The clinical experience from performing CSP has helped electrophysiologists gain deeper insight into the anatomy and physiology of cardiac conduction system. This review details the anatomy of the cardiac conduction system, and highlights some of the recently published articles that aid in better understanding of the AV conduction axis and its variations, the knowledge of which is critical for CSP. The remarkable evolution in technology has led to visualization of the cardiac conduction system using noninvasive, nondestructive high‐resolution contrast‐enhanced micro‐computed tomography imaging that may aid in future CSP. We also discuss from anatomical perspective, the differences seen clinically with His bundle pacing and left bundle branch area pacing.

Impact of His bundle pacing on right ventricular performance in patients undergoing permanent pacemaker implantation

“…Moreover, a lesser risk of TR could also be presumed with HBP by the fact that the lead tip and body are potentially above the tricuspid valve and within the right atrium 30–33 . However, recent anatomical studies showed HBP leads often penetrate the central fibrous body into the insulating tissues (representing the transition from the AV node to the bundle of His) on the atrial side of the hinge‐line in just over one‐half of the cases, and in the remainder either at the hinge‐line or on its ventricular aspect 34,35 . In agreement with this observation, we found HBP lead location below the TV in up to 43% of the cases; nevertheless, even though we appreciated a significant improvement in TR within each HBP subgroup of lead position (above and below the TV), we found no significant differences in TR severity between these two subgroups at 6‐months.…”

Biomechanical Identification of High-Risk Patients Requiring Permanent Pacemaker After Transcatheter Aortic Valve Replacement

“…In this study, we analyzed leaflet sectors of the aorticvalvular complex with respect to the need for PPI. Usually, patients requiring PPI had larger right coronary cusp (RCC) or noncoronary coronary cusp (NCC) sector calcification in the region of the leaflets (Dasi et al, 2017;Li and Sun, 2017;Lin et al, 2020;Padala et al, 2021). When a prosthesis was deployed within a severely and asymmetrically calcified leaflet during TAVR, there was a large pressure generated from the calcified leaflets.…”

Bioengineering the Cardiac Conduction System: Advances in Cellular, Gene, and Tissue Engineering for Heart Rhythm Regeneration

“…The right bundle branch travels toward the moderator band and the anterolateral papillary muscle. Lastly, they both culminate in the sub-endocardium, respectively, in the left and the right ventricles, by connecting with Purkinje fibers that contribute to the transmission of the electrical signal to the endocardial ventricular regions (Padala et al, 2021 ).…”

“…In the path toward natural rhythm restoration ( Figure 1 ), several technological advances are deeply contributing to an increased understanding of conductance (patho)physiology (Franco and Icardo, 2001 ; Goodyer et al, 2019 ; van Eif et al, 2020 ; Padala et al, 2021 ), as well as to its more feasible addressing for resolution. Methodologies based on naturally pacing cells, stem cell differentiation, gene engineering, tissue engineering, and/or their combination have been rehearsed so far in vitro and in vivo with varying success rates in restoring adequate cardiac pacing and conduction.…”