Pathological Features of Complete Atrioventricular Block in Dogs with Lymphocytic Myocarditis
T Sasaki1, C Saeki1, A Hirakawa2
1Laboratory of Veterinary Clinical Oncology, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo.
Journal of Comparative Pathology
|January 21, 2020
Summary
Lymphocytic myocarditis severely damages the cardiac conduction system, causing complete atrioventricular block. This inflammation destroys conduction fibers, leading to heart block in dogs.
Area of Science:
- Cardiology
- Veterinary Pathology
- Immunology
Background:
- Lymphocytic myocarditis is an inflammatory condition affecting the heart muscle.
- Complete atrioventricular (AV) block indicates a severe disruption in cardiac electrical signaling.
- Canine models are crucial for understanding cardiovascular diseases.
Purpose of the Study:
- To histologically examine the cardiac conduction system in dogs with lymphocytic myocarditis and complete AV block.
- To correlate inflammatory changes with structural alterations in the AV conduction system.
- To understand the pathological basis of AV block in this condition.
Main Methods:
- Histological examination of the cardiac conduction system.
- Analysis of myocardial tissue from 12 canine cases.
- Assessment of inflammatory cell infiltration and cardiomyocyte damage.
- Evaluation of fibrosis and conduction fiber integrity.
Main Results:
- Active lymphocytic myocarditis showed intense lymphoid infiltration and cardiomyocyte necrosis.
- Healing or healed myocarditis presented with cardiomyocyte loss and fibrosis.
- The AV conduction system was extensively involved, with loss of conduction fibers.
- Inflammatory destruction of the AV conduction system was observed throughout all heart chambers.
Conclusions:
- Lymphocytic myocarditis causes significant destruction of the AV conduction system.
- This destruction is the likely cause of complete AV block in affected dogs.
- The underlying cause of the lymphocytic myocarditis remains undetermined.
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