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September 2015

Cat: Heart, Excessive moderator bands in the left ventricle,
mild right ventricular dilatation, moderate bilateral atrial dilatation

08_15

History:

Cat, Chartreux, 9.5 years old, male neutered

Diagnoses:

Heart: Excessive moderator bands in the left ventricle, mild right ventricular dilatation, moderate bilateral atrial dilatation

Description:

A distinct network of increased numbers and size of moderator bands was present in the left cardiac ventricle. The right ventricle had mild dilatation, both atria moderate dilatation. The absolute heart weight was 19 g and the relative heart weight was not increased.

The lungs revealed a moderate, chronic, diffuse, alveolar edema accompanied by a moderate, chronic, diffuse, interstitial fibrosis and numerous alveolar macrophages with intracytoplasmic Prussion Blue-positive material (heart failure cells). Excessive interstitial connective tissue was also detected in the kidneys and the liver.

Comments:

Feline cardiomyopathies can be classified as hypertrophic, restrictive (endocardial fibrosis), dilated and excessive moderator band cardiomyopathy.

Clinical findings of cats with excessive moderator band cardiomyopathy include dyspnea, cardiomegaly, pleural effusion, pulmonary edema, heart murmurs, and aortic thromboembolism. Heart weights of affected cats are not significantly different from clinically normal cats. Typically, autopsy reveals a distinct network of excessive moderator bands in the left ventricle, left ventricular hypertrophy (with mean age, 4 years) or dilatation (with mean age, 8.7 years), and pulmonary edema with heart failure cells in the alveoli.

Microscopically, moderator bands (septomarginal trabecula) consist of Purkinje cells and mature collagen covered by endothelium.

The etiology of the excessive moderator band cardiomyopathy is unclear. It likely represents a congenital defect.

Picture and authored by Angele Breithaupt, Department of Veterinary Pathology, Freie Universit├Ąt Berlin, Germany