Primary histiocytic sarcoma of the aortic valve as a trigger of heart failure in a crossbreed dog A case of a histiocytic sarcoma at the aortic valve with multiple metastases in the ventricular myocardium, ventricular endocardium and mitral valves in a male crossbreed dog is described. Neoplasia resulted in inter mittent forward heart failure, thrombosis, myocardial infarction, and ventricular tachycardia.