Complete Atrioventricular Block Associated with Lymphocytic Myocarditis of the Atrioventricular Node in Two Young Adult Dogs

SummaryA histological investigation of the atrioventricular (AV) conduction system was performed in two young adult dogs with complete AV block. In both cases, infiltration of lymphocytes and plasma cells into the AV node and loss and disappearance of the conduction fibres were observed. Such inflammatory lesions of the AV conduction system were associated with complete AV block. The aetiology of these changes and the cause of its location at the AV node were not elucidated.