Chronic venous insufficiency or CVI is a medical condition where the veins cannot pump enough oxygen-poor blood back to the heart. It is sometimes referred to as an "impaired musculovenous pump", this is due to damaged or "incompetent" valves as may occur after deep vein thrombosis (when the disease is called postthrombotic syndrome) or phlebitis. Paratroopers, utility pole linemen, and men with leg injuries can suffer from damaged leg vein valves and develop this condition. Ordinarily, women make up the largest demographic for this problem.