SIGNALMENT: An 8-year-old, male, neutered, mixed-breed, dog, is examined. The dog presented to the emergency services deceased.

GROSS FINDINGS: One 3 x 2.5 x 1 cm lobulated, friable, smooth, mottled tan-dark, red thrombus is adhered to the right atrioventricular valve (AV) valve. Multi-focal to coalescing raised, granular, irregular, firm, tan foci are on the endocardium of the right auricle.  No significant abnormalities are observed in the brain and other organs of the abdominal and thoracic cavities.

DIAGNOSIS:  Peracute, complete right atrial thrombosis

REMARKS: The cause of death of this dog appears to be a large right AV valve and right atrial thrombosis likely leading to acute cardiac decompensation/failure.  However, the process which led to the thrombosis is not clear as no evidence of endocarditis or other processes which would predispose this animal to hypercoagulability, such as protein losing enteropathy/nephropathy, were observed.  Other conditions which may be less likely and were not apparent from gross and histologic examination on this case include atrial fibrillation/arrhythmias as well as endocrinopathies such as hyperadrenocorticism.

Heart, right auricle
Thrombus, right atrioventricular valve