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November 2015

Horse: Heart: mitral valve dysplasia with severe left ventricular hypertrophy, severe left atrial dilatation and moderate right ventricular dilatation

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Animal:

Horse, Warmblood, 16 years, female

Diagnosis:

Heart: mitral valve dysplasia with severe left ventricular hypertrophy, severe left atrial dilatation and moderate right ventricular dilatation

Description:

The left atrioventricular valve (mitral valve) presented with three instead of two cusps. The left ventricle was severe hypertrophic and the right ventricle was dilated (free wall of the left ventricle was up to six times thicker than the free wall of the right ventricle).

Comments:

The horse presented clinically with arrhythmia and collapse. Later on the animal developed severe tachycardia, intermittent asystole and severe subcutaneous edema in the presternal region. The horse was euthanized after all therapeutic attempts had failed.

At necropsy about 20 L of serous fluid were found in the abdominal cavity. The heart was enlarged with severe myocardial hypertrophy of the left ventricle and moderate to severe dilatation of the right ventricle. The mitral valve was malformed, presenting with three instead of two cusps. The myocardium had multifocal areas of pale discoloration, histologically consistent with chronic multifocal fibrosis with mild lymphoplasmacytic infiltration. Additionally, the lung presented severe alveolar and moderate chronic interstitial edema.

Congenital cardiac valve malformations are uncommon in horses. Mitral valve dysplasia is rather common in dogs, but is seen only rarely in horses. In contrast, congenital tricuspid valve anomalies in horses have been documented more frequently. The causes of these disorders are unknown.

 

Picture and authored by Aleksandra ┼╗uraw, Department of Veterinary Pathology, Freie Universit├Ąt Berlin, Germany