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Histological Features of the Atrioventricular Conduction System in Cats with High-Grade Atrioventricular Block

Noboru Machida1, Takafumi Sasaki1, Yusuke Kimura1

  • 1Laboratory of Veterinary Clinical Oncology, Tokyo University of Agriculture and Technology, Fuchu, Tokyo, Japan.

Journal of Comparative Pathology
|February 14, 2022
PubMed

Insights

Histopathological examination revealed that cats with high-grade atrioventricular block (H-AVB) had less severe lesions in the AV bundle’s branching portion compared to those with third-degree atrioventricular block (3-AVB). This may explain the intermittent nature of H-AVB.

Area of Science:

  • Veterinary Cardiology
  • Comparative Pathology
  • Cardiac Electrophysiology

Background:

  • Atrioventricular block (AVB) in cats can lead to syncopal attacks.
  • Understanding the histopathological basis of AVB severity is crucial for diagnosis and prognosis.
  • Previous studies have not fully elucidated the specific lesions associated with different grades of AVB in felines.

Purpose of the Study:

  • To compare the histopathological features of the atrioventricular (AV) conduction system in cats with high-grade AVB (H-AVB) and third-degree AVB (3-AVB).
  • To identify potential correlations between lesion severity in specific regions of the AV conduction system and the clinical presentation of AVB in cats.

Main Methods:

  • Histopathological examination of the AV conduction system in nine cats with H-AVB and 22 cats with 3-AVB.
  • Quantification of conduction fibre loss and fibrous replacement in the AV bundle branching portion and left bundle branch.
  • Comparison of lesion severity between the two groups.

Main Results:

  • Both H-AVB and 3-AVB cases showed significant loss of conduction fibres and fibrous replacement in the AV bundle branching portion and left bundle branch.
  • Cats with H-AVB exhibited less severe lesions in the AV bundle branching portion compared to cats with 3-AVB.
  • The severity of lesions in the left bundle branch was similar between the two groups.

Conclusions:

  • Differences in lesion severity, particularly in the AV bundle branching portion, may explain the intermittent nature of AV conduction block in H-AVB cases versus the permanent block in 3-AVB cases.
  • Histopathology of the AV conduction system is essential for differentiating between grades of AVB in cats.
  • Further research could explore the etiological factors contributing to these specific lesion patterns.

Keywords:
atrioventricular bundlecardiopathologycathigh-grade atrioventricular block

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