Venous thromboembolism (VTE) is a blood clot that starts in a vein. VTE encompasses two interrelated conditions: deep vein thrombosis (DVT), which is the development of a clot in the deep veins of the extremities or pelvis, and pulmonary embolism (PE), which occurs when a clot breaks free, usually from a deep vein in the legs, and becomes lodged in the lungs. Serious complications may result from VTEs so it is important to learn about the warning signs, symptoms and prevention.