SN explained that the problems with the veins in the legs may lead to chronic venous insufficiency ( CVI ). CVI means that there is a long-term problem with the veins not being able to pump blood back to your heart. When this happens, blood stays in the legs and causes swelling and aching. Two problems that may lead to chronic venous insufficiency are: Damaged valves. Valves keep blood flowing from the legs through the blood vessels and back to the heart. When the valves are damaged, blood does not flow as well. Deep vein thrombosis ( DVT ). Blood clots may form in the deep veins of the legs. This may cause pain, redness, and swelling in the legs. It may also block the flow of blood back to the heart. Seek immediate medical care if you have these symptoms. A blood clot in the leg can also break off and travel to the lungs. This is called pulmonary embolism ( PE ). In the lungs, the clot can cut off the flow of blood. This may cause chest pain, trouble breathing, sweating, a fast heartbeat, coughing (may cough up blood), and fainting. It is a medical emergency and may cause death. Call 911 if you have these symptoms. Healthcare providers call the two conditions,Deep vein thrombosis ( DVT ) and pulmonary embolism ( PE ), venous thromboembolism ( VTE ).