Seminars in respiratory and critical care medicine
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This review describes recent evidence relevant to the treatment of deep vein thrombosis (DVT) and pulmonary embolism (PE). Because venous thromboembolism (VTE) is a spectrum of disease that includes both of these disorders, many of the therapeutic options are common to both. At the time of diagnosis, effective treatment options for patients with VTE include unfractionated heparin, low molecular weight heparins (e.g., dalteparin, enoxaparin, tinzaparin), and pentasaccharides (e.g., fondaparinux). ⋯ Other treatment strategies such as vena caval filter placement and mechanical (or chemical) clot dissolution are discussed briefly. Anticoagulation with warfarin (or other oral vitamin K antagonists) is a highly effective strategy for the long-term prevention of VTE recurrence in most patients. In addition to presenting evidence relevant to the optimal duration of warfarin therapy, we highlight circumstances under which extended therapy with a parenteral agent such as a low molecular weight heparin might be preferable.
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Semin Respir Crit Care Med · Feb 2008
ReviewComputed tomography pulmonary angiography and venography: diagnostic and prognostic properties.
Computed tomography pulmonary angiography (CTPA) is now an established test in the diagnosis of suspected pulmonary embolism (PE). Some may argue that it has become the "one-stop" center for diagnosis and prognosis of acute PE and deep vein thrombosis (DVT). ⋯ The addition of computed tomography venography (CTV) increases the sensitivity, which may be worth the added radiation in certain patient populations. Although measures of right heart function, pulmonary artery pressures, and clot burden via CTPA need to be standardized and further validated prospectively, this test may also play a prominent role in determining short-term outcomes in patients with established acute PE.
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Massive pulmonary embolism (PE) with hemodynamic instability (e.g., hypotension and cardiac shock) is associated with a poor prognosis and high mortality rates (> 50%). Accordingly patients with massive PE should be treated aggressively with thrombolytic agents (or surgical or interventional procedures). Streptokinase, urokinase, and recombinant tissue plasminogen activator (rtPA) have been used, with generally similar results. ⋯ This article reviews indications for thrombolysis in massive PE, with an emphasis on recent data derived from normotensive patients. Further, we propose a diagnostic and therapeutic algorithm for treating acute PE. Additional studies are required to determine the benefit and safety of thrombolytic therapy for PE.
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Semin Respir Crit Care Med · Feb 2008
ReviewThrombophilias: when should we test and how does it help?
Venous thromboembolism can be a life-threatening event, occurring in ~1 in 1000 adults annually. An underlying cause for thrombosis can now be identified in up to 80% of cases, including both inherited and acquired causes of thrombophilia. ⋯ This article reviews both the inherited and the acquired causes of thrombophilia, focusing on the clinical scenarios in which these disorders should be suspected and on how to appropriately test for them when clinically indicated. By the conclusion of this article, the clinician should be equipped with an algorithm of how to approach a patient with a thromboembolic event, from decisions regarding which thrombophilia tests to order to how the results of these tests affect patient management.
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Heparin-induced thrombocytopenia (HIT) is a prothrombotic drug reaction caused by platelet-activating antibodies that recognize multimolecular complexes of platelet factor 4 (PF4) bound to heparin. HIT is an intense hypercoagulability state (increased thrombin generation in vivo) that is complicated more often by venous thromboembolism (deep vein thrombosis, pulmonary embolism) than by arterial thrombosis. HIT is a risk factor for coumarin-induced microthrombosis, particularly affecting acral regions of limbs with deep vein thrombosis (venous limb gangrene). ⋯ Recognition of HIT may be facilitated through the use of a clinical scoring system, the 4Ts ( Thrombocytopenia, Thrombosis, Timing, and o Ther explanations). Anti-PF4/polyanion enzyme-immunoassays (EIAs) and washed platelet activation assays readily detect HIT antibodies, and thus have high diagnostic sensitivity; however, only the platelet activation assays have high diagnostic specificity, suggesting that HIT is likely to be overdiagnosed in settings where EIAs are used exclusively for diagnosis. Treatment of HIT emphasizes substitution of heparin with an alternative nonheparin anticoagulant, such as a direct thrombin inhibitor (lepirudin, argatroban), or an indirect (antithrombin-mediated) inhibitor of factor Xa (danaparoid, fondaparinux?).