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American Journal of Medicine
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American Journal of Medicine
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Figure 7 highlights the specific recommendations for therapy and prevention of thrombosis from the latest guidelines from the ACCP.[4] These are evidenced-based recommendations by methodologists and represent a real resource for practicing clinicians worldwide. The current recommendation is that in patients with acute DVT of the leg, early (ie, the same day as parenteral treatment) initiation of a vitamin K antagonist (VKA) is recommended over delayed initiation, with continuation of parenteral anticoagulation for a minimum of 5 days and until the international normalized ratio (INR) for the VKA is ³ 2.0 for at least 24 hours.
This last point about the overlap is critically important. It really does not relate to factor VII, which is the factor that plummets dramatically early in the first 24 hours; rather this is important because of the long half-life of factor II, or thrombin. It literally takes days for the thrombin level to be suppressed or depressed sufficiently to prevent the propagation of clots. This means that as a physician you cannot start therapy with low molecular-weight heparin (LMWH) as soon as you see the INR increase to ³ 2.0, even on the third day. You might think of stopping the heparin, but you really cannot do that. There is an obligate overlap of about 4 to 5 days to allow the thrombin level to be suppressed.
In addition, as shown in the next recommendation, in patients with acute DVT of the leg, we suggest LMWH or fondaparinux over intravenous or subcutaneous unfractionated heparin. Hylek E. Am J Med 2013; published on-line at http://education.amjmed.com/00000.
[4] Kearon C, Akl EA, Comerota AJ, et al; American College of Chest Physicians. Antithrombotic therapy for VTE disease: Antithrombotic therapy and prevention of thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest. 2012;141(2 Suppl):e419S-e494S.