Corrigendum: A compact multi-functional model of the rabbit atrioventricular node with dual pathways.

[This corrects the article DOI: 10.3389/fphys.2023.1126648.].

A compact multi-functional model of the rabbit atrioventricular node with dual pathways.

The atrioventricular node (AVN) is considered a "black box", and the functioning of its dual pathways remains controversial and not fully understood. In contrast to numerous clinical studies, there are only a few mathematical models of the node. In this paper, we present a compact, computationally lightweight multi-functional rabbit AVN model based on the Aliev-Panfilov two-variable cardiac cell model. The one-dimensional AVN model includes fast (FP) and slow (SP) pathways, primary pacemaking in the sinoatrial node, and subsidiary pacemaking in the SP. To obtain the direction-dependent conduction properties of the AVN, together with gradients of intercellular coupling and cell refractoriness, we implemented the asymmetry of coupling between model cells. We hypothesized that the asymmetry can reflect some effects related to the complexity of the real 3D structure of AVN. In addition, the model is accompanied by a visualization of electrical conduction in the AVN, revealing the interaction between SP and FP in the form of ladder diagrams. The AVN model demonstrates broad functionality, including normal sinus rhythm, AVN automaticity, filtering of high-rate atrial rhythms during atrial fibrillation and atrial flutter with Wenckebach periodicity, direction-dependent properties, and realistic anterograde and retrograde conduction curves in the control case and the cases of FP and SP ablation. To show the validity of the proposed model, we compare the simulation results with the available experimental data. Despite its simplicity, the proposed model can be used both as a stand-alone module and as a part of complex three-dimensional atrial or whole heart simulation systems, and can help to understand some puzzling functions of AVN.

Electrocardiographic Approach to Complex Arrhythmias: P, QRS, and Their Relationships.

When faced with an electrocardiographic recoding of a complex arrhythmia, we often use inflexible algorithms or try to recall patterns already seen, which is often insufficient to explain the mechanisms of difficult bradycardias and tachycardias. We propose an approach to these situations where, starting from basic observations, the behavior of the different components of the arrhythmia is reconstructed using logical deductions. The extensive use of laddergrams faithfully illustrates how analysis of timing of each visible event, P and QRS, clarifies their relationship and dictates the behavior of electrocardiographic silent cardiac structures (sinus node and atrioventricular node).

General Introduction, Classification, and Electrocardiographic Diagnosis of Cardiac Arrhythmias.

The conduction system includes a primary pacemaker, the internodal tracts, the atrioventricular node, and the His bundle with the right and left branches. In "emergency" conditions, accessory pacemakers may be triggered. The conduction system produces very low-intensity currents; a surface electrocardiogram (ECG) detects only the big myocardial masses. Electrogenetic mechanisms are reduced automaticity and/or impaired conduction at the base of bradycardias. An increased automaticity and/or reentry phenomenon are at the base of ectopic beats and tachycardias. A "wide QRS" is a ventricular activation time of 120 milliseconds or more. The "laddergram" helps in the fast and reliable ECG interpretation.