What is Chronic Venous Insufficiency?
Author: Dr. Kim Langdon Cull
Anyone with diabetes is at risk for vascular disease that is either symptomatic or asymptomatic. Peripheral artery disease and venous insufficiency are two such vascular diseases. Both the heart and kidneys are at risk for vascular complications in people with diabetes.
In venous insufficiency, venous (not arterial) blood escapes from its normal flow back to the blood back to the heart and the blood leaks backward down the veins into an already swollen leg. Venous blood carries the blood with the least amount of oxygen and most amount of carbon dioxide for release in the lungs while arterial blood carries blood rich in oxygen after passing through the lungs. The veins have valves in them that keep the blood from pooling in the ankles and calves. With aging, poor genetics, and disease, these valves can become weakened and start to leak. Venous insufficiency is common and not a benign condition. Treatment of the symptoms and reversal of the underlying cause can be life saving.
Causes and Risk Factors for Venous Insufficiency
Untreated venous insufficiency in either the deep or superficial veins causes a chronic, progressive syndrome known as chronic venous insufficiency (CVI). In addition to the unsightly appearance of the legs, CVI can lead to life-threatening and poor healing infections (ulcers) of the lower extremities. Pain after walking is the primary symptom of the disease. CVI causes unique changes to the skin overlying the veins, called lipodermatosclerosis, which eventually results in ulceration .
The incidence of CVI increases with age as it does after a DVT, which damages venous valves causing backflow and increased venous pressure. A sedentary lifestyle minimizes the squeezing action of calf muscles on venous return to the heart and raises the internal blood pressure in the veins.
CVI occurs more frequently in obese women and in those who stand for long periods of time. There is a higher incidence of CVI in men who smoke. Diabetes and obesity can be two other risk factors for CVI.
Venous insufficiency syndromes are usually caused by valvular incompetence in either a low-pressure in the superficial venous system or from valvular weakening in the high-pressure deep venous system. Superfical valvular leaking results in varicose veins while the deep veins may lead to blood clots known as deep vein thrombosis (DVT).
When the veins are functioning correctly, every step or leg movement causes blood to be pumped inward towards the deep veins and upward past the valves.
After prolonged standing in a person with venous insufficiency, the veins are completely filled, and all the valves are pushed open. Failed valves cause the blood pressure in the vein to remain high even during ambulation. This increase pressure increases during and immediately after ambulation, which cause venous congestion or swelling. This type of turbulent blood flow can cause platelets to stick to the valve, forming a seed for a thrombus or blood clot.
How Does CVI Happen?
Venous hypertension in diseased veins is thought to cause CVI by reducing blood flow that ends up trapping white blood cells, which leads to enzyme release and the production of free radicals . Free radicals lead to oxidation or inflammation, and as the fluid build-ups, there is decreased oxygen to the tissue, and the propensity to release clotting factors. This loss of oxygen and clotting continues to damage tissue nearby. Any tissue with low oxygen and poor flow can lead to tissue death, phlebitis, blood clots, and ulcers.
The Process of CVI
There a various mechanisms associated with failure of superficial venous valves. Congenitally weak veins are most common and cause the walls to dilate under normal pressures, thus increasing pressure on the valves. Direct injury or superficial phlebitis may cause valve failure. For instance, under normal conditions, the calf muscles have 70% lower venous pressures with ambulation while diseased veins have only a 20% reduction in pressure. This steady and abnormal pressure causes venous stasis as the time for blood to circulate through the legs is prolonged. The blood backflow and venous stasis damages the valves even more which can lead to DVTs. Build-up of lactate and other metabolites can further damage veins and surrounding tissue, making them more prone to infections and non-healing leg or calf ulcers.
In a study done in San Diego, levels of circulating P-selectin were found to be directly correlated with the severity of CVI . P-selectin acts as a sticky substance in the vessels that may activate platelets and predispose to clots, further reducing tissue oxygen levels, all of which can lead to poor healing of sores and ulcers.
If nothing else, keep moving. Thirty minutes of walking at any speed can vastly reduce your chances of venous insufficiency, blood clots, and non-healing ulcers.
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• Bryan LJ, Callas PW, Criqui MH, Cushman M. Higher soluble P-selectin is associated with chronic venous insufficiency: the San Diego Population Study. Thromb Res. 2012 Nov. 130(5):716-9. [Medline].