A deep vein thrombosis (DVT) is a blood clot that forms in the deep large veins of the pelvis, lets, thighs or arms. A DVT can reduce or block blood flow in a vein. It may dislodge and travel in the bloodstream, causing a stroke, pulmonary embolism, heart attack, or death. DVT is a very serious condition and requires immediate medical attention. DVT’s may be treated with medications or surgery.