 Venous thromboembolism, or VTE, is when a clot forms in a deep vein, usually in the leg, then travels to the lungs and blocks blood supply. VTE affects around 600,000 Americans each year. You're at risk as you age, and if you've had recent surgery, a serious injury, or been still for a long time, from a hospital stay, bed rest, or travel. Also, if you have a personal or family history of deep vein clots,