Thrombosis may occur in three main ways, sometimes termed Virchow s triad. 2 thrombosis of the vena cava in cattle , which sometimes leads to a syndrome of pulmonary haemorrhage 3 thrombosis of the pulmonary artery in dogs with some types of renal glomerular disease and in some cases of Cushing s disease. Each of the examples illustrates a different pathogenesis. 1 Cardiomyopathy in cats is usually of the hypertrophic variety and associated with thickening of the walls of the heart.
Thrombi develop within the chambers due to abnormal blood flow within the heart.
Altered blood flow is one factor in development of thrombosis. In posterior vena caval thrombosis in cattle, the thrombus usually arises within the vena cava as it passes over the liver and develops due to phlebitis resulting from an underlying liver abscess . Embolism from the thrombus leads to inflammation within pulmonary arteries which may become weakened and dilated, leading to the formation of an aneurysm . Hypertension develops and pulmonary haemorrhage frequently develops. Damage to blood vessels is another of the mechanisms of thrombosis.