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Excessive Clotting Disorders

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Also known as: Hypercoagulable Disorders or States; Thrombophilia

What is an excessive clotting disorder?

An excessive clotting (hypercoagulable) disorder is a condition in which there is an increase in the risk of inappropriate blood clot (thrombus) formation. Also known as thrombophilia, it is the tendency of some people to develop blood clots in parts of the body, such as the deep veins in the legs or the arteries of the heart. The disorder may arise because of some underlying condition that develops during a person's lifetime (acquired) or may be due to certain genes passed from parent to child (inherited). In the U.S., more than 60,000 people die each year from venous thromboembolism, and many people who develop a clot experience long-term health issues, according to the Centers for Disease Control and Prevention (CDC).

Clotting is a normal response to blood vessel or tissue injury. When a blood vessel is injured, it begins to leak blood, either externally or into body tissues. The body stops this blood loss through a complex clotting process called hemostasis. During hemostasis, the injured blood vessel constricts to reduce blood flow, platelets adhere to the injury site and clump (aggregate) together to form a loose platelet plug, and the coagulation cascade is initiated. During the cascade process, the body sequentially activates coagulation factors, proteins that produce a net of fibrin threads that weave through the platelet plug and stabilize the resulting blood clot. This clot functions as a barrier to further blood loss, one that stays in place until the injury has healed.

Usually, the body activates the clotting process, regulates its speed and volume with feedback mechanisms, and after the site has healed, breaks down the clot and removes it in a process called fibrinolysis. Clotting disorders occur when something goes wrong with hemostasis and/or fibrinolysis. If the clotting process activates inappropriately, does not self-regulate properly, or the clot resists being broken down normally, then inappropriate, excessive blood clot formation may occur.

  • Activation problems: Some conditions cause activation of the clotting process when there is no injury and no need for a clot to form. For example, anything that interrupts the smooth blood vessel walls, essential for unimpeded blood flow, may increase risk of clot formation.
  • Regulation problems: Clot formation is carefully regulated by the body. Even as a clot forms to stop bleeding at the site of an injury, the body begins to activate proteins that will slow clot production, much like the brakes in a car. If clot production is not regulated well, excessive clotting may result.
  • Clot breakdown problems: After an injury is healed, proteins are activated that break down and remove the clot (fibrinolysis). Dysfunction or deficiency in the breakdown proteins can cause excessive clotting.

Deep Vein Thrombosis (DVT), Pulmonary Embolism (PE), Heart Attack and Stroke

Excessive clotting or thrombophilia can lead to the presence of a blood clot in a vein or artery that can potentially block the flow of blood and cause serious, life-threatening complications. Blood clots are referred to as thrombi (singular, thrombus) when they form in a blood vessel; thrombi may break off and block another blood vessel in another part of the body, where they are referred to as emboli (singular, embolus) or thromboemboli. Blood clots most commonly form in the deep veins of the lower legs (deep venous thrombosis, or DVT). They may grow very large and block blood flow in the legs, causing pain, swelling, and tissue damage.

While clots most commonly form in the veins of the legs, they may also form in other areas as well; for example, clots in coronary arteries are the cause of most heart attacks. Clots may also form on the lining of the heart or its valves, particularly when the heart is beating irregularly (atrial fibrillation) or when the valves are damaged. Clots also may form in large arteries as a result of narrowing and damage from atherosclerosis. Pieces of clots may also break off and cause an embolus that blocks an artery in another organ, such as the brain, where they can cause strokes, or lungs (pulmonary emboli), where they can cause chest pain and shortness of breath, or the kidneys.

There are a number of conditions, diseases and factors that can contribute to a person's risk of thrombosis. A person can have more than one factor or condition that increases their risk, and the resulting risk can be cumulative. For example, a person who has an inherited risk due to the presence of Factor V Leiden mutation will likely be at greater risk if they smoke or use oral contraceptives.

The next few pages describe several conditions and factors that can contribute to increased risk of thrombosis.

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