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Home / Equine Research Bank / Equine Vet J / Morphological evidence of a potential arrhythmogenic substra...
Equine veterinary journal2024; doi: 10.1111/evj.14075

Morphological evidence of a potential arrhythmogenic substrate in the caudal and cranial vena cava in horses.

Abstract: Three-dimensional electro-anatomical mapping, previously performed in horses with atrial arrhythmias, has demonstrated the medial region of the caudal vena cava (CaVC), 1-8 cm caudal to the fossa ovalis, as an anatomical predilection site for atrial tachycardia associated with areas of slow conduction and conduction block. Slow conduction has also been recorded in the cranial vena cava (CrVC). Objective: To investigate the morphological characteristics of the myocardial sleeves (MS) in the CaVC and CrVC, in order to identify a potential substrate of right sided atrial arrhythmias. Methods: Cross sectional. Methods: Post-mortem dissection of 37 hearts from adult warmblood horses without known cardiovascular disease. Macroscopic examination of the myocardial distribution, evaluated the MS area, length, width, and shape in the CaVC and the CrVC. At least 2 samples from each vena cava MS were histologically examined using Masson's trichrome staining. Results: Myocardial sleeves into the medial CaVC and into the CrVC were observed in all horses and showed variations in distribution, shape, and size between horses. Their mean ± standard deviation length from the limbus into the CaVC reached 5.7 ± 1.0 cm (maximum 8.3 cm), and from the azygos vein into the CrVC 5.3 ± 1.6 cm (maximum 8.6 cm). Myocardium-free islands were observed in the CaVC and CrVC in 30% and 6% of horses, respectively. Histologically, MS showed a non-uniform myocardial fibre arrangement, with presence of fibroadipose tissue, features known to result in slow conduction and pro-arrhythmia. Conclusions: Study only included horses without history of atrial arrhythmia. Conclusions: Myocardial sleeves are present in both CaVC and CrVC, showing anatomical variations between horses. Tissue characteristics known to favour re-entry were identified indicating that these venae cavae MS are a potential substrate for atrial tachyarrhythmias and a target for treatment by ablation. Background: La modélisation électro-anatomique tridimensionnelle, réalisée auparavant chez des chevaux souffrant d'arythmies atriales, a démontré que la région médiale de la veine cave caudale (CaVC), 1-8 cm caudalement à la fossae ovalis, représente un site anatomique de prédilection pour la tachycardie auriculaire associée à des zones de conduction ralentie et des blocs de conduction. Une conduction ralentie a aussi été enregistrée dans la veine cave crâniale (CrVC). Objective: Investiguer les caractéristiques morphologiques des manchons myocardiques (Myocardial sleeve;MS) dans les CAVC et CrVC, afin d'identifier un substrat potentiel d'arythmies atriales du côté droit du cœur. TYPE D'ÉTUDE: Étude transversale. MÉTHODES: Dissection post-mortem de 37 cœurs de chevaux à sang chaud adultes sans historique de maladie cardiovasculaire. Lors de l'examen macroscopique de la distribution myocardique, la surface des MS, leur longueur, largeur et forme ont été évaluées dans les CAVC et CrVC. Les MS ont été examinées microscopiquement dans au moins 2 échantillons de chaque veine cave, en utilisant la coloration de Masson Trichrome. RÉSULTATS: Les MS à l'aspect médial de la CaVC et à l'intérieur de la CrVC ont été inspectées chez tous les chevaux et ont montré des variations de distribution, forme et grandeur entre chevaux. Leur moyenne de longueur ± déviation standard du limbe de la fossae ovalis dans la CaVC était de 5.7 ± 1.0 cm (maximum 8.3 cm) et de la veine azygos dans la CrVC, de 5.3 ± 1.6 cm (maximum 8.6 cm). Des Îlots dénudés de myocarde ont été observé dans la CaVC et CrVC dans 30% et 6% des chevaux respectivement. À l'histologie, les MS ont montré des fibres myocardiques organisées de façon non-uniforme, avec présence de tissue fibroadipeux, caractéristiques connues pour entraîner une conduction lente et favoriser l'arythmie. Unassigned: Étude incluant seulement des chevaux sans historique d'arythmie atriale. Conclusions: Les MS sont présentes dans les CaVC et CrVC, démontrant les variations anatomiques entre chevaux. Des caractéristiques tissulaires connues pour favoriser une conduction ralentie ont été identifiés indiquant que les MS représentent un substrat potentiel des tachyarythmies atriales et une cible pour un traitement par ablation.
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Publication Date: 2024-02-23 PubMed ID: 38391272DOI: 10.1111/evj.14075Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This research article explores the structural properties of the caudal and cranial vena cava (CaVC and CrVC respectively) in horses, seeking to understand if these structures could be a source of right-sided atrial arrhythmias. The study examines the morphological characteristics of myocardial sleeves within these structures in 37 healthy horses.

Study Objective and Methods

  • The purpose of this research was to study the morphological features of the myocardial sleeves (MS), muscle tissue located in the CaVC and CrVC, to identify if these might contribute to atrial arrhythmias.
  • The study was cross-sectional and utilized post-mortem dissection of hearts from 37 adult warmblood horses with no known cardiovascular disease.
  • Examining the distribution of myocardial tissue, the researchers evaluated the area, length, width, and shape of the MS in the CaVC and CrVC.
  • For a detailed examination, at least 2 samples from each vena cava MS were histologically observed using Masson’s trichrome staining.

Research Findings

  • Myocardial sleeves in the medial region of the CaVC and CrVC were observed to be present in all the horses, but they showed variations in distribution, shape and size.
  • The average length of these sleeves into the CaVC was found to be 5.7 ± 1.0 cm (maximum 8.3 cm), and into the CrVC it was 5.3 ± 1.6 cm (maximum 8.6 cm).
  • Areas without myocardium, referred to as myocardium-free islands, were recorded in the CaVC and CrVC in 30% and 6% of horses, respectively.
  • On a microscopic level, MS displayed a non-uniform arrangement of myocardial fibre along with the presence of fibroadipose tissue, characteristics associated with slow conduction and likelihood of arrhythmia.

Conclusions

  • The study only considered horses without a known history of atrial arrhythmia. Nonetheless, it found that myocardial sleeves were evident in both CaVC and CrVC and that there were pronounced anatomical differences between horses in terms of these structures.
  • The physical attributes of the MS, specifically the non-uniform arrangement of myocardial fibre and the presence of fibroadipose tissue, were found to promote slow conduction – a condition that predisposes to re-entry, a phenomenon in cardiac electrophysiology that contributes to arrhythmias.
  • Therefore, the researchers conclude that these vena cava MS could be a potential substrate for atrial tachyarrhythmias in horses and may serve as a target for therapeutic intervention such as ablation.

Cite This Article

APA
Ibrahim L, Buschmann E, van Loon G, Cornillie P. (2024). Morphological evidence of a potential arrhythmogenic substrate in the caudal and cranial vena cava in horses. Equine Vet J. https://doi.org/10.1111/evj.14075

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English

Researcher Affiliations

Ibrahim, Lara
  • Department of Morphology, Imaging, Orthopedics, Rehabilitation and Nutrition, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium.
Buschmann, Eva
  • Equine Cardioteam Ghent, Department of Internal Medicine, Reproduction and Population Medicine, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium.
van Loon, Gunther
  • Equine Cardioteam Ghent, Department of Internal Medicine, Reproduction and Population Medicine, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium.
Cornillie, Pieter
  • Department of Morphology, Imaging, Orthopedics, Rehabilitation and Nutrition, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium.

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