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Venous thromboembolism (VTE) is a common and serious disorder characterized by pathologic blood clot formation that includes deep vein thrombosis (DVT) and pulmonary embolism (PE). The balance between hemostasis (normal cessation of bleeding) and thrombosis is a sensitive process influenced by genetics, concomitant medical conditions, and other risk factors. Three primary determinants of thromboembolism include venous stasis (eg, immobility or paralysis), vascular wall injury (eg, surgery or trauma), and hypercoagulability (eg, thrombophilia, cancer, pregnancy, genetics). Classic symptoms of a DVT include unilateral pain, swelling, erythema, and tenderness usually of the lower extremity; although some patients may be symptom-free. Compression ultrasound is typically used to diagnose a DVT. The symptoms of a PE are nonspecific and may include chest pain, shortness of breath, tachypnea, dyspnea, and hemoptysis. Most PEs originate from a DVT. The diagnosis of a PE is made by the presence of symptoms in conjunction with findings on computed tomography (CT) or a ventilation-perfusion (V/Q) scan. Medical work-up of patients presenting with VTE include determination of risk factors for VTE. Certain risk factors are reversible (eg, estrogen use, recent orthopedic surgery, smoking, prolonged immobility) and may be eliminated over time. The presence of irreversible or continuing risk factors (eg, cancer, thrombophilia, previous history of VTE) requires longer or an extended duration of therapy.

Key Definitions

  • Anticoagulation—the process of preventing blood clot formation

  • DVT—blood clot formation in a deep vein, usually in the leg (eg, deep femoral vein)

  • Postphlebitic syndrome—chronic condition occurring after DVT characterized by venous insufficiency, pain, edema, stasis dermatitis, varicose veins, and ulceration

  • PE—blockage of a pulmonary artery, usually from a thrombus that has traveled from another site, such as the deep vein of the leg

  • Thromboembolism—occlusion of a blood vessel due to a blood clot that has broken away and traveled from its place of origin

  • Thrombophilia—genetic or acquired predisposition to thrombosis

  • Thrombosis—pathologic blood clot formation


The goals of therapy in the management of VTE include preventing complications, such as thrombus extension, PE formation, VTE recurrence, mortality, and postphlebitic syndrome. Anticoagulants are the primary drug therapy used to achieve these goals and may be classified by basic mechanism of action into three groups: indirect thrombin inhibitors, direct thrombin inhibitors, and vitamin K antagonists. Both parenteral and some oral anticoagulants may be used for initial treatment of VTE. In most cases, patients receiving initial treatment with parenteral agents are transitioned to an oral anticoagulant for extended or indefinite therapy to prevent future thromboembolic events. In addition, anticoagulants are also used short- and long-term to prevent other thromboembolic events, including those associated with cardiac valve replacement and myocardial infarction; thromboembolic stroke prevention related to atrial fibrillation (SPAF), and VTE prevention in hospitalized or surgical patients at increased risk of thrombosis.


Indirect Thrombin Inhibitors

Heparin, low molecular weight heparins (LMWHs), ...

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