Health Conditions

Anticoagulants like warfarin are prescribed for people who are at increased risk of developing harmful blood clots; which are clumps that occur when blood hardens from a liquid to a solid.1 Individuals at risk for developing clots include people with certain types of irregular heartbeat, people with a mechanical heart valve, or those with disorders of the clotting system itself. Your doctor may have also prescribed warfarin if you have experienced a stroke, heart attack, a clot that traveled to the lung, or a clot in the leg.

Conditions that cause clots to form

Atrial Fibrillation (AF or Afib) is the common type of irregular heartbeat or heart rhythm that occurs in the upper champers of the heart (the atria). It affects about 4 percent of all people over 60 and almost 10 percent over 80.2 The atria does not empty all of the blood and as a result, the heart cannot pump as much blood as the body needs. Additionally, blood clots can form as a result of the blood not moving smoothly; which can then break free and potentially cause a stroke.

Prosthetic/Mechanical Heart Valves are used to replace or repair diseased heart valves. People with mechanical valves are often prescribed warfarin to prevent valve-associated strokes.3

Conditions of Interest - abnormal clot formation

Blood clots can form under many different circumstances and in different locations throughout the body. When clots form in the blood vessels or within the heart, it is called a thrombus.1 When a thrombus breaks loose and travels from one location in the body to another, it becomes an embolus. Eventually, these blood clots can lodge in blood vessels that are smaller than the size of the clot. These potentially fatal clots can lodge in the brain, heart tissue, or lungs, where they cause strokes, heart attacks, or pulmonary emboli.

Stroke is the third largest cause of death annually in the U.S., according to the American Stroke Association (ASA). About 780,000 Americans each year suffer a stroke, which means that every 40 seconds, someone in the U.S. has a stroke.4

Stoke is a term used for a rapid loss of brain function as a result of a problem in the vessels that supply blood and oxygen to the brain. This can either be due to a ischemia stroke, a lack of blood supply and oxygen caused by a blood clot, or to a hemorrhage, a blood vessels in the brain bursts. According to ASA, 80% of all strokes are ischemic or due to blood clots in the brain. 

Heart attacks are the leading cause of death in the U.S., with over 650,000 cases annually.4 A heart attack, also called a myocardial infarction, occurs when a section of the heart muscle gets damaged because of blood supply to the heart is interrupted. A blood clot is the most common cause of a blocked artery. Anticoagulants like warfarin, are often prescribed to help prevent clot formation after a heart attack.

Venous thromboembolism (VTE) consists of 2 related conditions: deep vein thrombosis (DVT) and pulmonary embolism (PE). This blood clot forms in the venous system and most often a DVT occurs when a deep vein in the leg is partially or completely blocked by the clot. DVT most frequently occurs following trama, major surgery, prolonged immobility (including airline travel), or in people with a clotting disorder. A PE most often occurs when one or more of these blood clots break off and lodges in the one of the veins in the lung.

  1. Lim W, Crowther MA, Ginsberg JS. Venous thromboembolism. In: Hoffman R, Benz EJ, Shattil SS, et al, eds. Hematology: Basic Principles and Practice. 5th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2008:chap 135.
  2. Lafuente-Lafuente C, Mah I, Extramiana F. Management of atrial fibrillation. BMJ. 2009;b5216.
  3. Goldhaber, S. “Bridging” and Mechanical Heart Valves. Circulation.2006; 113: 470-472.
  4. Lloyd-Jones D, Adams RJ, Brown TM, et al. Heart Disease and Stroke Statistics—2010 Update. A Report From the American Heart Association Statistics Committee and Stroke Statistics Subcommittee. Circulation. 2010;121:e1–e170.