Blood clots in the extremities don’t receive a lot of attention, but maybe they should. When clots break off and travel to the lungs, becoming "pulmonary emboli," they cause 200,000 deaths each year.

"Deep vein thrombosis" are clots in the deep veins. They usually originate in the calf muscles, though they can occur elsewhere. They are most common in persons who are immobilized, since pooling of blood is conducive to clot formation. Certain medical conditions (cancer, heart disease, obesity), genetic disorders of clotting mechanisms, and pregnancy are also associated with an increased risk of blood clots. They are also more common in persons over 40 and in women taking estrogen and other estrogen-related compounds, such as raloxifene (Evista).

To help prevent deep vein thrombosis from forming, keep moving! When traveling by car or air, or if you have a sedentary job, walk around every hour or so to enhance blood circulation. You might also flex and extend your ankles 10 times every half hour. If you are bedridden due to illness or surgery, get out of bed periodically, as you are able.

The symptoms of deep vein thrombosis are primarily pain and swelling of the leg or ankle. This may be accompanied by warmth and redness, and sometimes weakness. But about half the people who develop deep vein thrombosis experience no symptoms at all—chest pain caused by a pulmonary embolism may be the first sign. Also, shortness of breath, light-headedness, fainting, and irregular heartbeat may be signs of an embolism and should be considered true emergencies.

Blood clots are usually diagnosed with an ultrasound examination. Immediate treatment involve anticoagulants, especially intravenous heparin, which prevents existing blood clots from enlarging and additional clots from forming. Your physician may prescribe Warfarin taken orally, and new thrombolytic drugs or surgery may be indicated. While blood clots can be life-threatening to anyone, the elderly are particularly vulnerable. Fortunately, most healthy people recover well with appropriate treatment.

Sources:  The Merck Manual of Medical Information, Home Edition