Blood clotting, or coagulation, is an important process that prevents excessive bleeding when a blood vessel is injured. Platelets (a type of blood cell) and proteins in your plasma (the liquid part of blood) work together to stop the bleeding by forming a clot over the injury. Typically, your body will naturally dissolve the blood clot after the injury has healed. Sometimes, however, clots form on the inside of vessels without an obvious injury or do not dissolve naturally. These situations can be dangerous and require accurate diagnosis and appropriate treatment.
Clots can occur in veins or arteries, which are vessels that are part of the body’s circulatory system. While both types of vessels help transport blood throughout the body, they each function differently. Veins are low-pressure vessels that carry deoxygenated blood away from the body’s organs and back to the heart. An abnormal clot that forms in a vein may restrict the return of blood to the heart and can result in pain and swelling as the blood gathers behind the clot. Deep vein thrombosis (DVT) is a type of clot that forms in a major vein of the leg or, less commonly, in the arms, pelvis, or other large veins in the body. In some cases, a clot in a vein may detach from its point of origin and travel through the heart to the lungs where it becomes wedged, preventing adequate blood flow. This is called a pulmonary (lung) embolism (PE) and can be extremely dangerous.
It is estimated that each year DVT affects as many as 900,0001 people in the United States and kills up to 100,000.2 Despite the prevalence of this condition, the public is largely unaware of the risk factors and symptoms of DVT/PE. Do you understand your risk? Check out ASH’s five common myths about DVT.
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Arteries, on the other hand, are muscular, high-pressure vessels that carry oxygen- and nutrient-rich blood from the heart to other parts of the body. When your doctor measures your blood pressure, the test results are an indicator of the pressure in your arteries. Clotting that occurs in arteries is usually associated with atherosclerosis (hardening of the arteries), a deposit of plaque that narrows the inside of the vessel. As the arterial passage narrows, the strong arterial muscles continue to force blood through the opening, and the high pressure can cause the plaque to rupture. Molecules released in the rupture cause the body to overreact and form an unnecessary clot in the artery, potentially leading to a heart attack or stroke. When the blood supply to the heart or brain is completely blocked by the clot, a part of these organs can be damaged as a result of being deprived of blood and its nutrients.