Blood clots are a collection of sticky blood cells that form when a blood vessel is damaged. The body creates blood clots as a normal response to blood vessel damage. The main job of a blood clot is to seal the leak in a damaged blood vessel. This prevents the blood from leaking out and protects the person from bleeding.
Clots (or thrombi) that block the arteries and prevent flow of blood and oxygen to an organ can lead to areas of tissue damage (infarcts). When blood clots break away (called an embolism) from the area they’re meant to protect, they can endanger other organs.
Clots that block blood flow are the main culprits in most heart attacks and strokes. They can also damage other organs:
Presence of an obstructing blood clot (thrombus) is referred to as thrombosis. Thrombosis in a vein is almost always associated with phlebitis (inflammation of a vein). Thrombophlebitis is an inflammation of a vein in the area where a blood clot has formed.
Thrombophlebitis is classified as either superficial or deep. In other words, thrombosis can affect either superficial (surface) or deep (below the surface) veins, causing thrombophlebitis.
Superficial thrombophlebitis occurs when a blood clot affects veins near the skin surface, or superficial veins.
Deep venous thrombosis (DVT) occurs when a blood clot affects deeper, larger veins, such as those in the lower legs and thighs. DVT is more worrisome than superficial thrombophlebitis. These clots can break away (called emboli) from a blood vessel and cause a pulmonary embolism if they travel to the lung. (For more information on pulmonary embolism, see the section "Symptoms and Complications.") DVT is more common for people over 40 years of age.
Blood clots are the result of:
Ischemic strokes (strokes caused by blood clots blocking an artery that supplies the blood to the brain) can be due to blood clots that have formed in the heart as a result of rhythm disorders known as atrial fibrillation and atrial flutter.
Atrial fibrillation is a type of an irregular heartbeat (arrhythmia) that triggers a rapid, quivering beat in the upper chambers of the heart (the atria). This irregular pumping may cause some blood to remain in the heart chamber and form clots, which can then travel to the brain. Emboli can also form at the site of artificial heart valves, after a heart attack, or as a result of heart valve disorder or heart failure.
Cardiogenic embolism refers to clots that form inside the heart and travel to the brain. A stroke may occur in someone who has suffered a heart attack. A heart that has been damaged by a heart attack doesn’t pump blood properly, which can cause formation of a blood clot that travels to the brain. The presence of artificial replacement heart valves can also lead to blood clot formation. People with artificial heart valves can take blood-thinning medications to help to prevent clots from forming.
Some blood clots may form in a narrowed artery as a result of atherosclerosis, commonly known as hardening of the arteries. In this case, the arterial walls slowly thicken, harden, and narrow over time until blood flow is reduced. As a result, these arteries become vulnerable to injury. If they tear, a blood clot may form, completely blocking the already narrowed artery and shutting off oxygen to part of the heart or brain.
Blood clotting problems and rare blood disorders also cause blood clots to form, but the cause of blood clots is not always known.
For some women, the use of oral contraceptives (birth control pills) may increase the risk of blood clot formation. The risk is higher for women as they age, and for women who smoke or have a history of previous blood clots.
A variety of things can cause inflammation of a superficial vein. One common cause is due to trauma or injury, for example from solutions or medications given intravenously (into a vein) in hospitals. Piercing the vein to give the solution or medication can cause irritation. Any trauma to a vein (such as an injury from a car accident) will trigger inflammation in the area, leading to pain, discomfort, redness, and swelling. During this process, there is increased blood flow to the injured area, and a blood clot often forms in the inflamed or injured area of the vein. Superficial thrombophlebitis is an uncomfortable condition but rarely causes serious problems.
Sometimes, thrombophlebitis is caused by a bacterial infection in the vein. The usual culprit is a bacteria called Staphylococcus, commonly found on the skin.
In certain cases, thrombophlebitis develops without an obvious reason. It may develop in the leg veins of pregnant people, in people with varicose veins, and in some people with cancer in the abdomen (particularly the pancreas).
DVT occurs when blood clots form in the deep veins of the legs or pelvis, and is often caused by:
Certain inherited conditions can make DVT more likely to occur. Blood flow in the veins depends on contraction of surrounding muscles, and with inactivity, such as extended bed rest, the blood starts to collect and blood clots can easily form.
Medications are usually used to stop progression of DVT and prevent the blood clot from worsening, breaking away, and moving to the lungs. If you think you may have DVT, seek medical attention right away.
Blood-thinning medications such as warfarin*, heparin (either unfractionated heparin or low molecular weight heparins, like enoxaparin, dalteparin, or tinzaparin), fondaparinux, or oral anticoagulants (e.g., dabigatran, rivaroxaban, apixaban, edoxaban) are usually recommended. The choice of blood thinner is highly individualized; it is based on medical history, preference, other health issues, cost, and convenience. These medications may be continued for several months after a blood clot has been diagnosed. The length of treatment usually depends on whether it was a first episode or a recurrent event, whether the event was brought on by a specific issue or not, and whether there are other health issues (e.g., active cancer).
Most people do not require admission to a hospital to treat DVT, and those with DVT can usually return to normal activities within 2 to 3 weeks. If a pulmonary embolism is present and poses a risk of causing death, a more aggressive regimen of intravenous blood thinners may be used during a hospital admission (e.g., fondaparinux or dalteparin given in high doses, or alteplase).
For some people, long-term treatment with warfarin (an anticoagulant) or oral anticoagulants (e.g., dabigatran, rivaroxaban, apixaban) may be necessary to prevent new blood clots from forming. Your doctor may also recommend that you wear an elastic compression stocking on your leg to prevent DVT. Painkillers may be used to reduce the pain.
To relieve mild inflammation and discomfort, the affected area should be elevated and warm, moist packs applied for 15 to 20 minutes at a time throughout the day. For people with superficial thrombophlebitis, activities such as walking are recommended. If the inflammation and symptoms last longer than a day or two, or if symptoms become worse, see a doctor as soon as possible.
In cases where the thrombophlebitis is due to an infection, treatment with antibiotics often takes care of the problem. In rare cases, when the antibiotics aren’t enough to control the infection, surgical removal of the inflamed portion of the vein may be required.
To help prevent DVT, avoid long periods of immobility such as those during long car trips or airplane flights. Try to walk around and stretch for a few minutes every hour or so. Elevate your legs above your heart level if possible, and if you have a history of blood clots, wear support stockings or socks.
Prevention of blood clots is the best way to deal with the problems of heart disease and stroke. It is important to reduce or quit smoking and to control high blood pressure. High cholesterol levels also present a risk for blood clots and may be checked by your doctor. A healthy diet and regular exercise also help to reduce the risk of heart attack and stroke.
For more information, see our articles on heart attack and stroke.
All material copyright MediResource Inc. 1996 – 2025. Terms and conditions of use. The contents herein are for informational purposes only. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Source: www.medbroadcast.com/condition/getcondition/Blood-Clots
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