Inferior Extensions of the Atrioventricular Node

The pathways for excitation of the atrioventricular node enter either superiorly, as the so-called ‘fast’ pathway, or inferiorly as the ‘slow’ pathway. However, knowledge of the specific anatomical details of these pathways is limited. Most of the experimental studies that established the existence of these pathways were conducted in mammalian hearts, which have subtle differences to human hearts. In this review, the authors summarise their recent experiences investigating human cardiac development, correlating these results with the arrangement of the connections between the atrial myocardium and the compact atrioventricular node as revealed by serial sectioning of adult human hearts. They discuss the contributions made from the atrioventricular canal myocardium, as opposed to the primary ring. Both these rings are incorporated into the atrial vestibules, albeit with the primary ring contributing only to the tricuspid vestibule. The atrial septal cardiomyocytes are relatively late contributors to the nodal inputs. Finally, they relate our findings of human cardiac development to the postnatal arrangement.

Non-invasive Characterization of Human AV-Nodal Conduction Delay and Refractory Period During Atrial Fibrillation

During atrial fibrillation (AF), the heart relies heavily on the atrio-ventricular (AV) node to regulate the heart rate. Thus, characterization of AV-nodal properties may provide valuable information for patient monitoring and prediction of rate control drug effects. In this work we present a network model consisting of the AV node, the bundle of His, and the Purkinje fibers, together with an associated workflow, for robust estimation of the model parameters from ECG. The model consists of two pathways, referred to as the slow and the fast pathway, interconnected at one end. Both pathways are composed of interacting nodes, with separate refractory periods and conduction delays determined by the stimulation history of each node. Together with this model, a fitness function based on the Poincaré plot accounting for dynamics in RR interval series and a problem specific genetic algorithm, are also presented. The robustness of the parameter estimates is evaluated using simulated data, based on clinical measurements from five AF patients. Results show that the proposed model and workflow could estimate the slow pathway parameters for the refractory period, RminSP and ΔRSP, with an error (mean ± std) of 10.3 ± 22 and −12.6 ± 26 ms, respectively, and the parameters for the conduction delay, Dmin,totSP and ΔDtotSP, with an error of 7 ± 35 and 4 ± 36 ms. Corresponding results for the fast pathway were 31.7 ± 65, −0.3 ± 77, 17 ± 29, and 43 ± 109 ms. These results suggest that both conduction delay and refractory period can be robustly estimated from non-invasive data with the proposed methodology. Furthermore, as an application example, the methodology was used to analyze ECG data from one patient at baseline and during treatment with Diltiazem, illustrating its potential to assess the effect of rate control drugs.

Evaluation of the input site and characteristics of the antegrade fast pathway based on three-dimensional bi-atrial stimulus-ventricle mapping

Purpose Previous studies examined the right atrial (RA) input site of the antegrade fast pathway (AFp) (AFpI). However, the left atrial (LA) input to the atrioventricular (AV) node has not been extensively evaluated. In this study, we created three-dimensional (3-D) bi-atrial stimulus-ventricle (St-V) maps and analyzed the input site and characteristics of the AFp in both the RA and LA. Methods Forty-four patients diagnosed with atrial fibrillation or WPW syndrome were included in this study. Three-dimensional bi-atrial St-V mapping was performed using an electroanatomical mapping system. Sites exhibiting the minimal St-V interval (MinSt-V) were defined as AFpIs and were classified into seven segments, four in the RA (F, S, M, and I) and three in the LA (M1, M2, and M3). By combining the MinSt-V in the RA and LA, the AFpIs were classified into three types: RA, LA, and bi-atrial (BA) types. The clinical and electrophysiological characteristics were compared. Results AFpIs were most frequently observed at site S in the RA (34%) and M2 in the LA (50%), and the BA type was the most common (57%). AFpIs in the LA were recognized in 75% of the patients. There were no clinical or electrophysiological indicators for predicting AFpI sites. Conclusions Three-dimensional bi-atrial St-V maps could classify AFpIs in both the RA and LA. AFpIs in the LA were frequently recognized. There were no significant clinical or electrophysiological indicators for predicting AFpI sites, and 3-D bi-atrial St-V mapping was the only method to reveal the precise AFp input site.

Recognition of the anatomical structure of the atrioventricular node: Connection between the retroaortic node and the compact node

Introduction: The complex electrophysiological phenomena related to the atrioventricular node (AVN) are due to its complex anatomical structures. Aside from the inferior nodal extension (INE), other node-like tissues, such as the retroaortic node (RN), have been less described and may also share the mechanism of normal conduction and abnormal conduction in AVN re-entrant tachycardia (AVNRT). Methods: High-density sections of the entire AVN were obtained from rats and rabbits. Fibrosis was analyzed by Masson’s trichrome staining. Connexin (Cx43, Cx40, and Cx45) and ion channel (Nav1.5, Cav3.1, and HCN4) proteins were immunohistochemically labeled for the analysis of tissue features. Three-dimensional (3D) reconstruction of the AV junction was performed to clarify the relationships among different structures. Results: The RN expressed the same connexin isoforms as the compact node (CN) and INE. Nav1.5 labeling was present at a low level in the CN, RN and INE, where Cav3.1 and HCN4 were expressed. The CN connected with the RN in a narrow strip pattern at the level of the start of the CN. The RN presented as a shuttle shape and was the only tissue directly connected with the atrium in the anterior septum. Conclusion: The RN connects with the AVN anatomically, suggesting that there is direct electrical conduction between them. The entrance of the atria into the AVN is the distal part of the RN, which may form the fast pathway of the AVN.

Path Selection using Fuzzy Weight Aggregated Sum Product Assessment

The search for safe evacuation routes is an important issue to save flood victims so they can reach the evacuation centre. This research is a simulation of searching for safe and fast travel evacuation route that have 24 alternative routes. Every road that will be transverse has a limit with certain criteria. Calculate of the weight of the constraints using the Multi-Criteria Decision Making (MCDM) method, namely the Analytical Hierarchy Process (AHP) andWeight Aggregated Sum Product Assessment (WASPAS) based on Fuzzy logic. The criteria of obstacle that qualitative for obscurity so that it makes sense fuzzy will provide supportive input for the MCDM problem. The Fuzzy AHP method is applied to calculate the weight of an application while the Fuzzy WASPAS (WASPAS-F)method is used to determine the safest alternative route. By using the Fuzzy AHP and WASPAS-F methods, a safe and fast pathway weights 0.662

Electrophysiological changes in the conducting properties of fast pathway following modification of the slow pathway of the atrio ventricular node for atrio ventricular nodal re-entrant tachycardia

Objectives: To determine the possible changes in the conducting properties of the fast pathway after modification of the atrioventricular slow pathway for AVNRT which leads to the failure of the induction of tachycardia. Methods: This study was conducted in the Cardiac electrophysiology Laboratory of Hayatabad Medical Complex, Peshawar, Pakistan from March 2017 to March 2018. All the patients underwent radiofrequency modification of the slow pathway for AVNRT. Patients in whom typical AVNRT was inducible with demonstration of dual AV nodal physiology were included in the study. Results: A total of 171 cases were included in the study, 42 (25%) were males, mean age recorded was 47±15 years. There were no significant changes pre and post ablation in the base line parameters like VV interval, atrioventricular nodal (AV nodal) Wenckebach cycle length, slow pathway effective refractory period (SPERP) or fast and slow pathways maximal Atrio His interval. However significant change was observed in the effective refractory period of the fast pathway 350±49 Vs 290±32 (p value 0.0001). The difference between slow and Fast pathway ERP was also decreased significantly 82±36 Vs 56±24 (p value 0.004). Conclusion: Our study showed that ablation of AV nodal slow pathway for atrioventricular nodal reentrant tachycardia leads to changes in the effective refractory period of the fast pathway. doi: https://doi.org/10.12669/pjms.35.5.473 How to cite this:Khan I, Shah B. Electrophysiological changes in the conducting properties of fast pathway following modification of the slow pathway of the atrio ventricular node for atrio ventricular nodal re-entrant tachycardia. Pak J Med Sci. 2019;35(5):---------. doi: https://doi.org/10.12669/pjms.35.5.473 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.