This is the Secretary and former First Lady's second reported blood clot, or thrombosis. In a previous interview with the New York Daily News, Mrs. Clinton related an episode in 1998 when her foot became swollen and painful. It was a time when she was campaigning and frequently traveling on airplanes. Her doctors diagnosed a blood clot. "That is the most significant health scare I've ever had," she told the Daily News in October, 2007.The most common kind of blood clot, a deep venous thrombosis, or DVT, tends to arise when flow slows down within a vein, typically in a person's leg. Clots arise when platelets and fibrous proteins clump and stick to a vessel wall. This can be a normal, healthy response to trauma - whether that's a nick upon shaving or surgical incision. In people disposed to DVT, the small clots don't dissolve properly or may form in the absence of trauma. If a clot expands and propagates from below the knee, for example, to a more central position in the body, that's called an embolism. Clots are most dangerous when and if they spread to arteries in the lungs, causing pulmonary embolism, or to vessels in the brain.The CDC estimates that between 300,000 and 600,000 individuals sustain DVTs and pulmonary embolism in the United States each year, and that between 60, 000 and 100,000 of those are events are lethal. Some people inherit a disposition to clotting that can be evaluated by blood tests. Clots are most common in people who've been immobilized, such as after surgery, or are bed-bound with illness. Dehydration compounds the risk. Coach class syndrome refers to the proclivity of some to develop clots upon long-distance travel in a cramped position.Other risk factors for DVT include some malignancies. Cancer, depending on its position, can impede blood flow from the lower body, promoting stasis in the leg veins, or otherwise interfere with clot-dissolving proteins. Some women with autoimmune conditions, like lupus and other syndromes, may be disposed to clotting in veins or arteries. Some medications pose a risk, too. Those include estrogen-containing oral contraceptives and hormone replacement therapy. In general, high-estrogen states dispose to pathologic blood clots. In younger women, the disposition to blood clotting can manifest during pregnancy.As far as we know, the cause of Mrs. Clinton's blood clot is uncertain. She is in the hospital being treated with blood thinners. Usually people who have significant blood clots in a deep vein or artery take an anti-coagulant for a period of months. Until recent years, the standard treatment involved injections of heparin, or similar blood thinners, followed by Coumadin, an oral anticoagulant that requires frequent blood checks. Now, there are more options for therapy, including heparin-like agents that can be injected at home.On November 2 of this year, the FDA approved Xarelto (rivaroxaban) for treatment of deep venous thrombosis. This new drug, a pill, works by inhibiting a clotting factor called Xa. While several oral anticoagulants have received approval for prevention of clots in people undergoing surgery, and for prevention of strokes in people with disposing heart problems, Xarelto is the first in this new class of drugs that might be prescribed for treatment of DVT or pulmonary embolism.Before her recent admission to the hospital, the Secretary of State hadn't said much about what she'll do when she exits her official office. Popular views include that she'll get more rest, exercise, spend time with her family, write a book and, possibly, run for President in 2016. Today, she's presumably resting and, together with her doctors, sorting out the factors that led to her developing a significant blood clot. Good to know that she, like any other informed patient, has several treatment options to consider.Update: The U.S. State Department issued an update on Mrs. Clinton's condition, clarifying that the Secretary of State has a blood clot in a vein near the inside of the skull, on the right side. According to their statement, she has not suffered a stroke or neurological damage. Photo: State Department's Tumblr Follow Scientific American on Twitter @SciAm and @SciamBlogs. Visit ScientificAmerican.com for the latest in science, health and technology news.
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