From the Guidelines
The conduction system of the heart is located within the heart tissue itself, with key components including the sinoatrial node, atrioventricular node, bundle of His, and bundle branches, which are situated in specific areas such as the right atrium, interventricular septum, and ventricular myocardium. The bundle of His, a crucial part of this system, is a ventricular structure located within the membranous portion of the ventricular septum, as described in the 2020 ACC expert consensus decision pathway on management of conduction disturbances in patients undergoing transcatheter aortic valve replacement 1. This pathway highlights the importance of understanding the regional anatomy of the conduction system and the atrioventricular septum, particularly in the context of transcatheter aortic valve replacement (TAVR) and the risk of permanent pacemaker (PPM) implantation.
The conduction system's anatomy is complex, with the bundle of His emerging at an obtuse angle and the right bundle running superficially through the upper third of the right ventricular endocardium 1. The left bundle, on the other hand, is located on the left ventricular side of the muscular septum. The atrioventricular (AV) septum, which separates the right atrium and the left ventricle, is also a critical area, as valve implantation that overlaps with the distal AV septum may affect both the right and left bundles, leading to complete AV block 1.
Key points about the conduction system's location include:
- The sinoatrial node is situated in the right atrium near the entrance of the superior vena cava
- The atrioventricular node is positioned in the lower right atrium near the tricuspid valve
- The bundle of His is located in the interventricular septum
- The bundle branches extend down the respective sides of the septum
- The Purkinje fibers spread throughout the ventricular myocardium, as generally described in the context of cardiac conduction 1.
Understanding the precise location and anatomy of the conduction system is essential for clinical decision-making, particularly in procedures like TAVR, where the risk of conduction disturbances and the need for PPM implantation are significant concerns 1.
From the Research
Location of the Conduction System in the Heart
The cardiac conduction system (CCS) is a complex network of specialized cells and tissues responsible for initiating and coordinating the heartbeat. The location of the CCS in the heart can be described as follows:
- The sino-atrial node, atrioventricular node, and His-Purkinje system are the main components of the CCS 2.
- The sino-atrial node is located in a specific position, which has been redefined using immunohistochemistry and anatomical techniques 2.
- The atrioventricular node is also located in a specific area, and its anatomy has been redefined to allow for the computation of its physiological and pathophysiological behavior 2.
- The His-Purkinje system, including the bundle branches and Purkinje fibers, is distributed throughout the ventricles 3.
- Additional components of the CCS, such as the tricuspid, mitral, and aortic rings, and a third (retro-aortic) node, have been identified, although their role in the initiation and coordination of the heartbeat is not fully understood 2.
Development and Structure of the Conduction System
The CCS develops from the primary myocardium of the linear heart tube during embryological development, under the influence of the transcription factor Tbx3 2.
- The specialized cardiac conduction system consists of the sinoatrial node and the atrioventricular conduction system, which includes proximal and distal components 4.
- The expression of specific markers, such as Cx45 and HCN4, can be used to identify the sinoatrial node and distinguish it from the working myocardium 4.