FREE SHIPPING over $40
OVER 10000 FIVE-STAR REVIEWS
5% OFF ALL SUBSCRIPTIONS
100% HAPPINESS GUARANTEE
Analyze Diet
0
Veterinary world2023; 16(10); 2173-2185; doi: 10.14202/vetworld.2023.2173-2185

Histopathological changes in the electrical conduction of cardiac nodes after acute myocardial infarction in dogs and horses, compared with findings in humans: A histological, morphometrical, and immunohistochemical study.

Abstract: The heart conduction system is responsible for the occurrence of various types of cardiac arrhythmia. This study aimed to histologically and morphometrically describe damaged cardiac nodes during acute myocardial infarction and to compare them with normal tissues in dogs and horses. Unassigned: This study describes the morphometry of cardiac nodes in five dogs and five elderly horses that succumbed to sudden cardiac death (SCD). A computerized morphometric study was conducted to determine the number of cells composing the nodes, different shape and size parameters of nodes, and their relationship with degenerative changes due to cardiac conditions. Unassigned: In both species, the sinoatrial node (SAN) was ovoid in shape whereas the atrioventricular node (AVN) was pyramidal in shape. The percentage of collagen fibers inside the SAN of dogs (47%) and horses (50%) was found to be higher than that of cells. In contrast, the percentage of cells in the AVN of dogs (24%) and horses (16%) was higher than that of connective tissues. In the SAN, the area (p = 0.09), maximum diameter (<0.001), and mean diameter (0.003) of P cells were larger in dogs than in horses. Unassigned: Overall, the SAN cells and surrounding cardiomyocytes in dogs and horses as well as the AVN cells in dogs that succumbed to SCD decreased in size compared with those in normal hearts.
Copyright: © Gómez-Torres, et al.
Get Full Text
Publication Date: 2023-10-25 PubMed ID: 38023272PubMed Central: PMC10668561DOI: 10.14202/vetworld.2023.2173-2185Google Scholar: Lookup
The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
LinkedInCopy
  • Journal Article

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.

Overview

  • This study examines the microscopic structural changes in the heart’s electrical conduction nodes after acute myocardial infarction (heart attack) in dogs and horses.
  • The researchers compared damaged and normal cardiac nodes to understand the histological and morphometric differences that may contribute to sudden cardiac death (SCD).

Introduction and Purpose

  • The heart’s conduction system, including the sinoatrial node (SAN) and atrioventricular node (AVN), controls heart rhythm and is crucial for normal cardiac function.
  • Damage to these nodes can lead to arrhythmias, which are irregular heartbeats that may cause sudden cardiac death.
  • The study aimed to describe structural changes in these nodes after acute myocardial infarction in two animal species—dogs and horses—and compare findings with human data.

Methods

  • Five dogs and five elderly horses that died suddenly due to cardiac causes were studied.
  • A computerized morphometric analysis was conducted to quantify:
    • The number of cells within the nodes.
    • Shape and size parameters of the nodes.
    • Proportion of collagen fibers (connective tissue) versus cells within the nodes.
  • Histological examinations were used to look at tissue architecture and cellular changes.
  • Immunohistochemical methods were likely used to identify specific cell types and proteins, although details are not provided in the abstract.

Key Findings

  • Shape of Nodes:
    • Both dogs and horses showed an ovoid shape in the sinoatrial node (SAN).
    • The atrioventricular node (AVN) had a pyramidal shape in both species.
  • Composition Differences:
    • In the SAN:
      • Collagen fibers made up approximately 47% of the tissue in dogs and 50% in horses, indicating a high amount of connective tissue relative to cells.
    • In the AVN:
      • Cell percentages were higher than collagen fibers—24% in dogs and 16% in horses—showing a denser cellular structure compared to the SAN.
  • Size Differences:
    • P cells (pacemaker cells responsible for initiating the heartbeat) in the SAN were larger in dogs than in horses:
      • Area showed a trend to be larger in dogs (p=0.09).
      • Maximum diameter was significantly larger in dogs (p < 0.001).
      • Mean diameter was also significantly larger in dogs (p = 0.003).
  • Degenerative Changes:
    • In animals that died of sudden cardiac death (SCD), SAN cells and surrounding cardiomyocytes in both dogs and horses showed a decrease in size compared with normal hearts.
    • Similarly, AVN cells in dogs that succumbed to SCD were reduced in size.

Interpretation and Significance

  • The increased collagen in the SAN suggests fibrosis or scarring, which can disrupt normal electrical conduction and potentially cause arrhythmias.
  • The larger size of pacemaker cells in dogs compared to horses may point to species-specific differences in cardiac structure and function.
  • The observed shrinking of conduction cells and surrounding heart muscle in affected animals aligns with degenerative changes after acute myocardial infarction.
  • These changes could impair the conduction system’s ability to maintain normal heartbeat, thus explaining the risk for sudden cardiac death.
  • Comparing these findings to humans could enhance understanding of how myocardial infarction leads to fatal arrhythmias and help develop better diagnostic or treatment strategies for preventing sudden cardiac death in veterinary and human medicine.

Summary

  • This study provides detailed histological and morphometric insights into the structural alterations of cardiac conduction nodes following acute myocardial infarction in dogs and horses.
  • It highlights key differences in fibrosis and cell size that contribute to node dysfunction and sudden death.
  • Understanding these changes helps explain the mechanisms behind cardiac arrhythmias and identifies potential targets for clinical intervention.

Cite This Article

APA
Gómez-Torres F, Ballesteros-Acuña L, Ruíz-Sauri A. (2023). Histopathological changes in the electrical conduction of cardiac nodes after acute myocardial infarction in dogs and horses, compared with findings in humans: A histological, morphometrical, and immunohistochemical study. Vet World, 16(10), 2173-2185. https://doi.org/10.14202/vetworld.2023.2173-2185

Publication

Veterinary world
ISSN: 0972-8988
NlmUniqueID: 101504872
Country: India
Language: English
Volume: 16
Issue: 10
Pages: 2173-2185

Researcher Affiliations

Gómez-Torres, Fabián
  • Department of Basic Sciences, School of Medicine, Universidad Industrial de Santander, Bucaramanga, Colombia.
Ballesteros-Acuña, Luis
  • Department of Basic Sciences, School of Medicine, Universidad Industrial de Santander, Bucaramanga, Colombia.
Ruíz-Sauri, Amparo
  • Department of Pathology, Faculty of Medicine, Universitat de Valencia, Valencia, Spain.
  • INCLIVA Biomedical Research Institute, Valencia, Spain.

Conflict of Interest Statement

The authors declare that they have no competing interests.

References

This article includes 52 references
  1. Janse M.J.. Electrophysiological changes in heart failure and their relationship to arrhythmogenesis.. Cardiovasc. Res. 2004;61(2):208–217.
    pubmed: 14736537
  2. Roberts W, Salandy S, Mandal G, Holda M.K, Tomaszewksi K.A, Gielecki J, Tubss R.S, Loukas M. Across the centuries:Piecing together the anatomy of the heart.. Transl. Res. Anat. 2019;17:100051.
  3. Haissaguerre M, Cheniti G, Escande W, Zhao A, Hocini M, Bernus O. Idiopathic ventricular fibrillation with repetitive activity inducible within the distal Purkinje system.. Heart Rhythm. 2019;16(8):1268–1272.
    pmc: PMC6659587pubmed: 30980946
  4. Liberthson R.R, Nagel E.L, Hirschman J.C, Nussenfeld S.R, Blackbourne B.D, Davis J.H. Pathophysiologic observations in prehospital ventricular fibrillation and sudden cardiac death.. Circulation. 1974;49(5):790–798.
    pubmed: 4828598
  5. Lie J.T.. Histopathology of the conduction system in sudden death from coronary heart disease.. Circulation. 1975;51(3):446–452.
    pubmed: 1139756
  6. Gómez-Torres F.A, Ballesteros-Acuña L.E, Ruíz-Saurí A. Histological and morphometric study of the components of the sinus and atrio-ventricular nodes in horses and dogs.. Res. Vet. Sci. 2019;126:22–28.
    pubmed: 31421508
  7. Keith A, Flack M. The form and nature of the muscular connections between the primary divisions of the vertebrate heart.. J. Anat. Physiol. 1907;41(Pt 3):172–189.
    pmc: PMC1289112pubmed: 17232727
  8. Zichaa S, Fernández-Velasco M, Lonardo G, L'Heureux N, Nattel S. Sinus node dysfunction and hyperpolarization-activated (HCN) channel subunit remodeling in a canine heart failure model.. Cardiovasc. Res. 2005;66(3):472–481.
    pubmed: 15914112
  9. Carmona-Puerta R, Lorenzo-Martínez E. The normal sinus node:What we now know.. Corsalud. 2020;12(4):415–424.
  10. Padala S.K, Cabrera J.A, Ellenbogen K.A. Anatomy of the cardiac conduction system.. Pacing Clin. Electrophysiol. 2021;44(1):15–25.
    pubmed: 33118629
  11. Arshad A, Atkinson A.J. A 21st century view of the anatomy of the cardiac conduction system.. Transl. Res. Anat. 2022;28:100204.
  12. James T.N, Sherf L, Fine G, Morales A.R. Comparative ultrastructure of the sinus node in man and dog.. Circulation. 1966;34(1):139–163.
    pubmed: 5942665
  13. Kawashima T, Sato F. First in situ 3D visualization of the human cardiac conduction system and its transformation associated with heart contour and inclination.. Sci. Rep. 2021;11(1):8636.
    pmc: PMC8060315pubmed: 33883659
  14. Thiyagarajah A, Lau D.H, Sanders P. Atrial fibrillation and conduction system disease:The roles of catheter ablation and permanent pacing.. J. Interv. Card. Electrophysiol. 2018;52(3):395–402.
    pubmed: 30074119
  15. Johnson M.S, Martin M.W.S, Henley W. Results of pacemaker implantation in 104 dogs.. J. Small. Anim. Pract. 2007;48(1):4–11.
    pubmed: 17212742
  16. Visser L.C, Keene B.W, Mathews K.G, Browne W.J, Chanoit G. Outcomes and complications associated with epicardial pacemakers in 28 dogs and 5 cats.. Vet. Surg. 2013;42(5):544–550.
    pubmed: 23662684
  17. Peters C.H, Sharpe E.J, Proenza C. Cardiac pacemaker activity and aging.. Annu. Rev Physiol. 2020;82:21–43.
    pmc: PMC7063856pubmed: 31756134
  18. Logantha S.J.R.J, Yamanushi T.T, Absi M, Temple I.P, Kabuto H, Hirakawa E, Quigley G, Zhang X, Gurney A.M, Hart G, Zhang H, Dobrzynski H, Boyett M.R, Yanni J. Remodelling and dysfunction of the sinus node in pulmonary arterial hypertension.. Phil. Trans. R. Soc. B. 2023;378(1879):202220178.
    pmc: PMC10150205pubmed: 37122221
  19. Ward J.L, DeFrancesco T.C, Tou S.P, Atkins C.E, Griffith E.H, Keene B.W. Outcome and survival in canine sick sinus syndrome and sinus node dysfunction:93 cases (2002–2014). J. Vet. Cardiol. 2016;18(3):199–212.
    pubmed: 27286907
  20. DeLay J. Postmortem findings in Ontario racehorses, 2003–2015.. J. Vet. Diagn. Invest. 2017;29(4):457–464.
    pubmed: 28382856
  21. Boden L.A, Charles J.A, Slocombe R.F, Sandy J.R, Finnin P.J, Morton J.M, Clarke A.F. Sudden death in racing thoroughbreds in Victoria, Australia.. Equine. Vet. J. 2005;37(3):269–271.
    pubmed: 15892239
  22. Diab S.S, Poppenga R, Uzal F.A. Sudden death in racehorses:Postmortem examination protocol.. J. Vet. Diagn. Invest. 2017;29(4):442–449.
    pubmed: 28114865
  23. Kiryu K, Nakamura T, Kaneko M, Oikawa M, Yoshihara T. Cardiopathology of sudden cardiac death in the racehorse.. Heart Vessels Suppl. 1987;2:40–46.
    pubmed: 3449504
  24. Lyle C.H, Uzal F.A, McGorum B.C, Aida H, Blissitt K.J, Case J.T, Charles J.T, Gardner I, Horadagoda N, Kusano K, Lam K, Pack J.D, Parkin T.D, Slocombe R.F, Stewart B.D, Boden L.A. Sudden death in racing Thoroughbred horses:An international multicentre study of post mortemfindings.. Equine. Vet. J. 2011;43(3):324–331.
    pubmed: 21492210
  25. De Lange L, van Steenkist G, Vera L, de Clerq D, Decloedt A, Cromheeke K.M.C, van Loon G. First Successful Application of a Closed Loop Stimulation Pacemakers with Remote Monitoring in Two Syncopal Miniature Donkeys.. Valencia, Spain: Proceedings of the 12th ECEIM Congress; 2019. p. 87.
  26. James T.N. Anatomy of the AV node of the dog.. Anal. Rec. 1964;148:15–20.
    pubmed: 14115506
  27. Denes P, Wu D, Dhingra R, Amat-y-Leon F, Wyndham C, Rosen K.M. Dual atrioventricular nodal pathways. A common electrophysiological response.. Br. Heart J. 1975;37(10):1069–1076.
    pmc: PMC482921pubmed: 1191420
  28. De Almeida M.C, Sanchez-Quintana D, Davis N, Charles F.R, Chikweto A, Sylvester W, Loukas M, Anderson R.H. The Ox atrioventricular conduction axis compared to human in relation to the original investigation of Sunao Tawara.. Clin. Anat. 2020;33(3):383–393.
    pubmed: 31749249
  29. Moe G.K, Cohen W, Vick R.L. Experimentally induced paroxysmal AV nodal tachycardia in the dog. A “case report”.. Am. Heart. J. 1963;65(1):87–92.
  30. Cabrera J.A, Anderson R.H, Macias Y, Nevado-Medina J, Porta-Sanchez A, Rubio J.M, Sanchez-Quintana D. Variable arrangement of the atrioventricular conduction axis within the triangle of Koch:Implications for permanent His bundle pacing.. JACC. Clin. Electrophysiol. 2020;6(4):362–377.
    pubmed: 32327069
  31. Wilson C, Zi M, Smith M, Hussain M, D´Souza A, Dobrzynski H, Boyett M.R.. Atrioventricular node dysfunction in pressure overload-induced heart failure-Involvement of the immune system and transcriptomic remodelling.. Front. Pharmacol. 2023;14:1083910.
    pmc: PMC10110994pubmed: 37081960
  32. Lo H.M, Lin F.Y, Cheng J.J, Tseng Y.Z. Anatomic substrate of the experimentally-created atrioventricular node re-entrant tachycardia in the dog.. Int. J. Cardiol. 1995;51(3):273–382.
    pubmed: 8586476
  33. Kay G.N, Epstein A.E, Dailey S.M, Plumb V.J. Selective radiofrequency ablation of the slow pathway for the treatment of atrioventricular nodal re-entrant tachycardia. Evidence for involvement of perinodal myocardium within the re-entrant circuit.. Circulation 1992;85(5):1675–1683.
    pubmed: 1572026
  34. Kaneshige T, Machida N, Yamamoto S, Nakao S, Yamane Y. A histological study of the cardiac conduction system in canine cases of mitral valve endocardiosis with complete atrioventricular block.. J. Comp. Path. 2007;136(2–3):120–126.
    pubmed: 17362978
  35. Gómez-Torres F.A, Ruíz-Saurí A. Morphometric analysis of the His bundle (atrioventricular fascicle) in humans and other animal species. Histological and immunohistochemical study.. Vet. Res. Commun. 2021;45(4):319–327.
    pubmed: 34244914
  36. Kalyanasundaram A, Li N, Hansen B.J, Zhao J, Fedorov V.V. Canine and human sinoatrial node:Differences and similarities in the structure, function, molecular profiles, and arrhythmia.. J. Vet. Cardiol. 2019;22:2–19.
    pmc: PMC6436970pubmed: 30559056
  37. Machida N, Hirakawa A. The anatomical substrate for sick sinus syndrome in dogs.. J. Comp. Path. 2021;189:125–134.
    pubmed: 34886980
  38. Semelka M, Gera J, Usman S. Sick sinus syndrome:A review.. Am. Fam. Physician. 2013;87(10):691–696.
    pubmed: 23939447
  39. Demoulin J.C, Kulbertus H.E. Histopathological correlates of sinoatrial disease.. Br. J. Cardiol. 1978;40(12):1384–1389.
    pmc: PMC483583pubmed: 737096
  40. Glukhov A.V, Hage L.T, Hansen B.J, Pedraza-Toscano A, Vargas-Pinto P, Hamlin R.L, Weiss R, Carnes C.A, Billman G.E, Fedorov V.V. Sinoatrial node re-entry in a canine chronic left ventricular infarct model:Role of intranodal fibrosis and heterogeneity of refractoriness.. Circ. Arrhythm. Electrophysiol. 2013;6(5):984–994.
    pmc: PMC3904863pubmed: 23960214
  41. Monfredi O, Boyett M.R. Sick sinus syndrome and atrial fibrillation in older persons-a view from the sinoatrial nodal myocyte.. J. Mol. Cell. Cardiol. 2015;83:88–100.
    pubmed: 25668431
  42. Nakao S, Hirakawa A, Fukushima R, Kobayashi M, Machida N. The anatomical basis of bradycardia-tachycardia syndrome in elderly dogs with chronic degenerative valvular disease.. J. Comp. Pathol. 2012;146(2–3):175–182.
    pubmed: 21612788
  43. Hansen B.J, Zhao J, Csepe T.A, Moore B.T, Li N, Jayne L.A, Kalyanasundaram A, Lim P, Bratasz A, Powell K.A, Simonetti O.P, Higgins R.S.D, Kilic A, Mohler P.J, Janssen P.M.L, Weiss R, Hummel J.D, Fedorov V.V. Atrial fibrillation driven by micro-anatomic intramural re-entry revealed by simultaneous sub-epicardial and sub endocardial optical mapping in explanted human hearts.. Eur. Heart. J. 2015;36(35):2390–2401.
    pmc: PMC4568403pubmed: 26059724
  44. Van Loon G, Fonteyne W, Rottiers H, Tavernier R, Deprez P. Implantation of a dual-chamber, rate-adaptive pacemaker in a horse with suspected sick sinus syndrome.. Vet. Rec. 2002;151(18):541–545.
    pubmed: 12448492
  45. Keen J.A. Pathological bradyarrhythmia in horses.. Vet. J. 2020;259–260:105463.
    pubmed: 32553234
  46. Holmes JR. Heart block in the horse. Cardiac Rhythm 1987;p. 364.
  47. Liu SK, Hsu FS, Lee RCT. Diseases of conduction system. An Atlas of Cardiovascular Pathology 1989;pp. 125–128.
  48. Ertelt A, Bertram CA, Zuraw A, Gehlen H. A third degree AV-block in a horse with a putative regular rhythm and physiological heart rate in general examination. Pferdeheilkunde Equine Med 2018;34(5):414–418.
  49. Marolf V, Mirra A, Fouché N, de Solis CN. Advanced atrioventricular blocks in a foal undergoing surgical bladder repair:First step to cardiac arrest?. Front Vet Sci 2018;5:96.
    pmc: PMC6008567pubmed: 29951488
  50. Van Loon G. Cardiac arrhythmias in horses. Vet Clin North Am Equine Pract 2019;35(1):85–102.
    pubmed: 30871832
  51. Yoshimura A, Yamaguchi T, Kawazato H, Takahashi N, Shimada T. Immunohistochemistry and three-dimensional architecture of the intermediate filaments in Purkinje cells in mammalian he arts. Med Mol Morphol 2014;47(4):233–239.
    pubmed: 24570344
  52. Nooma K, Saga T, Iwanaga J, Tabira Y, Watanabe K, Tubbs RS, Yamaki KI. A novel method with which to visualize the human sinuatrial node:Application for a better understanding of the gross anatomy of this part of the conduction system. Clin Anat 2020;33(2):232–236.
    pubmed: 31444825

Citations

This article has been cited 1 times.
  1. Krawczyk-Ożóg A, Stachowicz A, Szoniec G, Batko J, Stachyra K, Bolechała F, Strona M, Wołkow PP, Yin Z, Dobrzynski H, Hołda MK. Proteomic profile of human sinoatrial and atrioventricular nodes in comparison to working myocardium.. Sci Rep 2025 Feb 28;15(1):7238.
    doi: 10.1038/s41598-025-89255-ypubmed: 40021668google scholar: lookup
Subscribe to our newsletter
Join 100,280 horse owners like you who receive our email updates on horse health and nutrition.