Cats with severe heart disease are at risk for the formation of blood clots that may block circulation and deprive tissues of oxygen. This tissue insult causes sudden and severe pain, paralysis and/or organ failure, and often proves fatal. A new strategy to prevent this devastating complication of heart disease is urgently needed. Based on efforts in human medicine, the researchers aim to use a novel approach based on specific blockade of a key coagulation protein called tissue factor (TF). In this study, researchers propose to develop an assay to detect TF activity on feline white blood cells and to produce a recombinant feline-specific TF inhibitor that may prevent clot formation in feline cardiac patients.