Deep vein thrombosis, DVT, kills more people each year than HIV, cancer, and traffic accidents combined. DVT is essentially a clot in the deep veins of the thighs or pelvis, but it can be in the upper extremity and / or the lower extremity. The way it forms is due to a number of potential causes. Sometimes with injury, sometimes with what we call a hypercoagulable state, meaning the patient has a risk factor for developing clots, and sometimes for sitting or laying for prolonged periods, such as a long flight. Patients develop a clot in the deep veins of the legs. And then these clots can break up and go to the lungs, which can cause damage to the lungs called a pulmonary embolism. If patients have a connection between the right and left heart, such as what we call a patent foramen ovale, the clot could actually transit from the leg to the brain and cause a stroke.