2.5 Additional Reading:Venous Thromboembolism
What is venous thromboembolism？
Venous thromboembolism（VTE）is a blood clot that starts in a vein.It is the third leading vascular diagnosis after heart attack and stroke，affecting about 300，000 600，000 Americans each year.There are two types：deep vein thrombosis（DVT）and pulmonary embolism（PE）.
Deep vein thrombosis
DVT is clotting of blood in a deep vein of an extremity（usually calf or thigh）or the pelvis.DVT is the primary cause of pulmonary embolism.DVT results from conditions that impair venous return，leading to endothelial injury or dysfunction，or cause hypercoagulability.DVT may be asymptomatic or cause pain and swelling in an extremity；pulmonary embolism is an immediate complication.Diagnosis is by history and physical examination and is confirmed by objective testing，typically with duplex ultrasonography.D-Dimer testing is used when DVT is suspected；a negative result helps to exclude DVT，whereas a positive result is nonspecific and requires additional testing to confirm DVT.Treatment is with anticoagulants.Prognosis is generally good with prompt and adequate treatment.Common long-term complications include venous insufficiency with or without the postphlebitic syndrome.
DVT occurs most commonly in the lower extremities or pelvis.It can also develop in deep veins of the upper extremities（4%to 13%of DVT cases）.
Lower extremity DVT is much more likely to cause pulmonary embolism，possibly because of the higher clot burden.The superficial femoral and popliteal veins in the thighs and the posterior tibial and peroneal veins in the calves are most commonly affected.Calf vein DVTis less likely to be a source of large emboli but can propagate to the proximal thigh veins and from there cause PE.About 50%of patients with DVT have occult PE，and at least 30%of patients with PEhave demonstrable DVT.
Pulmonary embolism
PEoccurs when a DVT clot breaks free from a vein wall，travels to the lungs and blocks some or all of the blood supply.Blood clots in the thigh are more likely to break off and travel to the lungs than blood clots in the lower leg or other parts of the body.PE is a relatively common vascular disease with potentially life-threatening complications in the short term.The accurate incidence of the condition is unknown，but it is estimated that 200，000 to 500，000 patients are diagnosed with PE each year in the United States.Many of these cases are diagnosed in the emergency department.Traditionally，patients with PEare treated in the hospital（usually for 24 hours but up to 5 or 6 days）for initiation of anticoagulation therapy and monitoring for any clinical deterioration.The introduction of low molecular weight heparin（LMWH）and the nonvitamin K-dependent oral anticoagulants，together with the increased ability to accurately stratify patients according to their risk of short-term clinical deterioration，have made it potentially feasible and safe to manage selected low-risk patients in the outpatient setting either entirely or after a short in-hospital observation period.
What causes VTE？
DVTs form in the legs when something slows or changes the flow of blood.The most common triggers for DVT and PE are surgery，cancer，immobilization and hospitalization.In women，pregnancy and use of hormones like oral contraceptives or estrogen for menopause symptoms are also important.Clotting is more likely to happen in people who are older，obese or overweight，or have conditions such as cancer or autoimmune disorders such as lupus.It occurs more often in people whose blood is thicker than normal because too many blood cells are made by bone marrow.Genetic causes of excessive blood clotting are also important.These occur when there are changes in the genetic code of some proteins needed for clotting or proteins that work to naturally dissolve blood clots in the body.VTEis most common in adults aged above 60，but it can occur at any age.VTEis rare in children.(https://www.daowen.com)
How is VTE diagnosed？
Blood work may be done initially，including a test called D-dimer，which detects clotting activity.For DVT，an ultrasound of the leg is most often used.For PE，computed tomography（CT or CAT scan）is most often used.Sometimes a ventilationperfusion lung scan is used.Both tests are able to see intravenous dyes in the arteries of the lung，looking for blockages by clots.
How can VTE be prevented？
VTEs are often preventable，with strategies that stop the development of clots in people“at-risk”.Healthcare professionals discern risk by gathering information about a patient’s age，weight，medical history，medications and lifestyle factors.Those at risk may take anti-clotting or blood-thinning medications or use mechanical devices such as compression stockings or compression devices.If possible，getting out of bed quickly after surgery is also advised.
How is it treated？
Treatment usually includes blood-thinning medications to keep clots from continuing to form and sometimes strong clotbusters to actually break up clots.Options include anticoagulants，including injectables such as heparin or LMWH，or tablets such as apixaban，dabigatran，rivaroxaban，edoxaban and warfarin，and thrombolytic therapy such as a tissue plasminogen activator（TPA）—a clot-dissolving enzyme.This can be given through an arm vein，and also by inserting catheters directly into the blood clot in the vein or lung.Surgical procedures may also be used.This can involve placing a filter in the body’s largest vein to prevent blood clots from traveling to the lungs.It can also involve removing a large blood clot from the vein or injecting clotbusting medicines into the vein or lung artery.
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Task 9 Identify the word elements and define the meaning of each medical term.
