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Sometimes a thrombus detaches itself from the wall and is carried along by the bloodstream. Such a clot is called an embolus, and the condition is known as embolism. A thrombus may form in the heart chambers, such as after coronary thrombosis (see below) at the place where the wall of the heart is weakened, or in the dilated atria in a case of mitral stenosis. Because blood normally flows more slowly through the veins than through the arteries, thrombosis is more common in veins than in arteries.
In thrombosis of superficial veins, bed rest with legs elevated and application of heat to the affected area may be all that is necessary. In thrombosis of deep veins, the affected part must be immobilized to prevent the clot from spreading or turning into an embolus, and anticoagulant drugs may be given. With proper treatment, recovery occurs within a short time unless an embolism develops. Practice management guidelines for venous thromboembolism in trauma patients note that a vena cava filter should be considered in patients at high risk who are not candidates for anticoagulants.
In advanced cases of arteriosclerosis, a thrombus may fill up whatever channel remains through a vessel, completely blocking off circulation and causing gangrene. This occurs most frequently in arteries of the legs and is called peripheral thrombosis. The onset, often sudden, is characterized by either a tingling feeling or numbness and coldness in the limb. Pain is not always present. Immediate treatment with anticoagulants is necessary to discourage clotting. If this is not effective, surgery may be required. This condition is most common in the elderly and in diabetics. There are now methods of treatment that may save the limb, such as surgical removal of a thrombus or embolus, or surgery of blood vessels to remove old, narrowed, or deteriorated vessels and replace them with grafts.
thrombosis(throm-bo'sis) [ thrombo- + -osis]
Trauma (particularly after an operation and parturition), cardiac and vascular disorders, obesity, hereditary coagulation disorders, age over 65, an excess of erythrocytes and of platelets, an overproduction of fibrinogen, and sepsis are predisposing causes.
Lungs: Obstruction of the smaller vessels in the lungs causes an infarct that may be accompanied by sudden pain in the side of the chest, similar to pleurisy; also present are the spitting of blood, a pleural friction rub, and signs of consolidation. Kidneys: Blood appears in the urine. Skin: Small hemorrhagic spots may appear in the skin. Spleen: Pain is felt in the left upper abdomen. Extremities: If a large artery in one of the extremities, such as the arm, is suddenly obstructed, the part becomes cold, pale, bluish, and the pulse disappears below the obstructed site. Gangrene of the digits or of the whole limb may ensue. The same symptoms may be present with an embolism.
If the limb is swollen, one should watch for pressure sores. Burning with a hot water bottle or electric pad should be guarded against. Prolonged bedrest may be necessary, depending on the patient's condition.
Pathological clots are treated with thrombolytic agents (such as streptokinase), antiplatelet drugs (such as heparins or aspirin), anticoagulants (such as warfarin), or platelet glycoprotein receptor antagonists (such as abciximab). When a thrombus or embolus is large and life threatening, surgical removal may be attempted.
cardiac thrombosisCoronary occlusion.
cerebral sinovenous thrombosis
coronary thrombosisCoronary occlusion.
deep vein thrombosis, deep venous thrombosis Abbreviation: DVT
DVT results from one or more of the following conditions: blood stasis, e.g., bedrest; endothelial injury, e.g., after surgery or trauma; hypercoagulability, e.g., factor V Leiden or deficiencies of antithrombin III, protein C, or protein S; congestive heart failure; estrogen use; malignancy; nephrotic syndrome; obesity; pregnancy; thrombocytosis; or many other conditions. DVT is a common occurrence among hospitalized patients, many of whom cannot walk or have one or more of the other risk factors just mentioned.
The patient may report a dull ache or heaviness in the limb, and swelling or redness may be present, but just as often patients have vague symptoms, making clinical diagnosis unreliable.
Compression ultrasonography is commonly used to diagnose DVT (failure of a vein to compress is evidence of a clot within its walls). Other diagnostic techniques include impedance plethysmography and venography.
Unfractionated heparin or low molecular weight heparin (LMWH) is given initially, followed by several months of therapy with an oral anticoagulant such as warfarin. The duration of therapy depends on whether the patient has had previous thrombosis and whether, at the end of a specified period of treatment, the patient has an elevated D-dimer level: patients with increased D-dimers after several months of treatment with anticoagulants are more likely than other patients to have recurrent clots if their anticoagulant regimen is discontinued..
Pulmonary emboli are common and may compromise oxygenation or result in frank cardiac arrest. Postphlebitic syndrome, a chronic swelling and aching of the affected limb, also occurs often.
In hospitalized patients and other immobilized persons, early ambulation, pneumatic compression stockings, or low doses of unfractionated heparin, LMWH, or warfarin may be given to reduce the risk of DVT.
effort thrombosisPaget-Schreutter syndrome
hepatic vein thrombosis
mural thrombosisMural thrombus.
postpartum ovarian vein thrombosis
Stents are deployed in completely obstructed or partially blocked arteries to keep blood flowing through them to the organs they supply. When this blood flow stops due to clotting within the stent, the organ may become ischemic and die. To reduce the risk of clotting within a stent, patients use antiplatelet drugs, like aspirin, dipyridamole, or clopidogrel, and medications to lower serum lipid levels. Tobacco cessation, and healthy lifestyle changes (eating lighter, exercising regularly) may also be helpful.
Patient discussion about venous thrombosis
Q. Are long flights dangerous? I'm flying next week to my vacation, and the flight is going to be rather long (almost 16 hours non-stop). Several years ago, my 75 years-old aunt had blood clot in her lung after a flight of similar length. I also heard that during flight the blood in the legs clots and that it can cause after that problems with the lungs and breathing. Does this mean it's dangerous for me to fly? Should I change my ticket to shorter connection flights?
Q. How can I prevent blood clots? I am 45 years old and am supposed to go on a business trip overseas. The flight itself is 12 hours long and then I have to continue traveling by bus. Could this cause me to have blood clots? If so, how can I prevent it?