Deep vein thrombosis is a medical condition in which blood clots develop in the deep veins of the body, often in the legs, thigh or pelvis. These clots can break loose and travel to the lungs and can cause a life-threatening condition called pulmonary embolism. An IVC filter is a small, basket-like device made of wire that’s inserted into the inferior vena cava to capture the blood clots, and prevent them from reaching the lungs.