Blood Must Flow
Deep veins lie deep inside your body among groups of muscles. They lead to the vena cava, your body's largest vein. The vena cava runs directly to your heart. The blood in your deep leg veins must fight against gravity to return to your heart, and it is helped in this by the squeezing of your leg muscles when you move your legs and feet. The valves in your veins help this process as well: when your leg muscles relax, they close to prevent the blood from flowing back down the legs. These actions together are termed the venous pump.
When you walk or run, the venous pump works well to return blood to the heart. But when you sit or stand, especially for long periods of time, blood can stop flowing and pool in your deep veins. If blood pools for a long period of time, blood clots can form. This condition is called deep vein thrombosis (DVT).
Blood clots may form in the veins of the arms or pelvis as well, but the ones that form in the deep veins of the legs are most likely to become emboli. This may be because the squeezing action of the calf muscles can dislodge a blood clot in a deep vein.
Blood clots can also form in the veins close to the surface of the skin in a condition known as superficial vein thrombosis or phlebitis. However, these clots aren't considered dangerous, as they don't usually become emboli and often disappear of their own accord.
Other causes of DVT include surgery, bone fractures, obesity, heart attack, childbirth, being at very high altitudes, hormone therapy or birth control pills, cancer, and genetic disorders.
Symptoms of DVT
About half the people who have DVT have no symptoms in the affected area. When symptoms do occur, the affected limb or the neck may swell, be painful to the touch, look red, and feel warm.
Post-thrombotic syndrome is chronic deep vein insufficiency that occurs after DVT. In chronic deep vein insufficiency, blood clots in the deep veins heal by becoming scar tissue. This damages valves in the veins. Fluid accumulates (edema) and the ankle swells. If the blockage is higher up, the calf and even the thigh can swell as well. The edema generally subsides overnight, because the veins are able to empty when the legs are horizontal.
In some cases the affected veins can be destroyed altogether, and the edema is always present. There may be throbbing pain when the person stands or walks. The skin of the ankle becomes flaky and itchy and may turn reddish brown in color. This skin is very vulnerable to injury, and even a minor scrape can break it open and cause an ulcer. If the edema persists, scar tissue develops and traps fluid in the tissue. The calf becomes hard and permanently enlarged, and ulcers become both more likely to develop and less likely to heal.
What Are Thrombosis & Embolism? (VIDEO)
Your Blood Moves
Thrombus & Embolus
Symptoms & Risk Factors
Blood Must Flow
Consequences of Clots
Tests & Diagnosis for DVT
Prevention & Treatment
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