The purpose of blood clotting in healthy people is to stop bleeding during an injury. In this process, blood hardens from a liquid to a solid state, or coagulates. Sometimes blood clots form without an injury, blocking blood vessels and even causing serious health conditions.
Normal Blood Clotting
Normal blood clotting---coagulation---requires a cascade of different enzymes---clotting factors. It begins when platelets stick to a blood vessel at the site of an injury. The injury activates the first enzyme, which activates the next, until a clot is formed from a protein called fibrin around the platelets. Once the clotting factors accomplish their functions they are degraded and removed from the place of injury, preventing unnecessary clotting.
Abnormal Blood Clotting
A blood clot formed within blood vessels or heart is called a thrombus. If a thrombus detaches and travels through the blood it is an embolus and the condition is called embolism. Thrombi and emboli can block the blood flow in vessels, preventing the oxygen from reaching the tissues---ischemia---resulting in tissue damage if not treated quickly. People with the blood that cannot clot normally have bleeding disorders, which make them bleed for a longer time than non-affected people. The most common are Willebrand disease and hemophilia.
Causes of Abnormal Clotting
Blood clots form when blood flow is slowed down. Risk factors include family history, surgery, injuries, prolonged sitting or laying, smoking, obesity, heart failure, giving birth in the last six months, medications, such as birth control pills, or certain blood disorders. Willebrand disease is inherited, and the patients' platelets cannot stick together or attach to blood vessel walls. Hemophilia is a usually inherited, but very rare, and the affected people miss one of the clotting factors.
Consequences of Abnormal Clotting
When blood clots form in deep veins in the lower leg they can cause deep venous thrombosis, and the thrombus can detach and travel through the blood causing potentially life-threatening conditions. In arterial embolism clots block an artery and deprive surrounding tissue from oxygen, causing damage. If a clot travels to the heart, it can cause a heart attack, in the lungs a pulmonary embolism and in the brain a stroke. If untreated, blood disorders can lead to loss of a lot of blood, and even anemia---too little red blood cells in the blood.
Symptoms of Clotting Problems
Symptoms of blood clotting disorders include shortness of breath, pain in the chest, sudden weakness or numbness in the face, arm or leg, sudden difficulty speaking or understanding, sudden disturbed vision. The Mayo Clinic advises to seek emergency care if experiencing such symptoms. The major symptoms of bleeding disorders are excessive bleeding and easy bruising.
Prevention and Treatment
The first step in prevention is to identify the source of a blood clot. Doctors can prescribe blood thinners, such as warfarin, or antiplatelet drugs, such as aspirin. Physical activity, wearing pressure stockings, quitting smoking improve blood flow and reduce the risk of clotting. Drugs thrombolytics can dissolve clots, but some people need surgery for clot removal. People with severe bleeding problems need daily medicines. The main treatment for hemophilia is injecting the missing or insufficient clotting factor.
