After consulting with his doctors, Cheney was asked to return to George Washington University Hospital for repeat ultrasound imaging of the clot in that leg, said spokeswoman Megan McGinn.Pain after the acute development of a DVT is usually caused by thrombophlebitis - an inflammation of the veins. This is usually improved after treatment with anticoagulants and analgesics. The time-course of Mr. Cheney's current discomfort might herald something more insidious and problematic: post-phlebitic syndrome.
"The ultrasound revealed no extension or complication of the clot," she said. "His blood-thinning medication was found to be therapeutic. These results are expected and reassuring."
Post phlebitic syndrome is thought to be cause by disruption of the venous valves from a pre-existing blood clot. These venous valves help shuttle blood back toward the heart. When the venous valves are damaged (as from the development of a clot), elevations in pressure within the venous system of the leg causing venous hypertension (from eMedicine.com):
Two major mechanisms in the body prevent venous hypertension. First, bicuspid valves in the veins prevent backflow and venous pooling. DVTs commonly occur at these valves, causing irreversible damage to the valve. Second, during normal ambulation, calf muscles decrease venous pressures by approximately 70% in the lower extremities. With rest, pressures return to normal in approximately 30 seconds. In diseased veins, ambulation decreases venous pressures by only 20%. When ambulation is stopped, pressure in the vein lumen increases slowly, returning to normal over a period of minutes.Looks like Dick might need to lay low a while and wear those compression stockings. Otherwise, he could risk the serious complications of venous disease like a venous stasis ulcer.
Venous hypertension in diseased veins is thought to cause CVI (chronic venous insufficiency) by the following sequence of events. Increased venous pressure transcends the venules to the capillaries, impeding flow. Low-flow states within the capillaries cause leukocyte trapping. Trapped leukocytes release proteolytic enzymes and oxygen free radicals, which damage capillary basement membranes. Plasma proteins, such as fibrinogen, leak into the surrounding tissues, forming a fibrin cuff. Interstitial fibrin and resultant edema decrease oxygen delivery to the tissues, resulting in local hypoxia. Inflammation and tissue loss result.