Venous thromboembolism: identifying patients at risk and establishing prophylaxis

Venous thromboembolism (VTE) is a major cause of morbidity and mortality and is associated with substantial healthcare costs. Identification of patients at risk of developing VTE enables appropriate thromboprophylaxis to be implemented. Although no predisposing risk factors can be identified in many patients in whom VTE develops, most have at least one underlying risk factor which can be categorized according to whether it confers low, moderate, or high risk. Clinical trials have demonstrated the effectiveness of thromboprophylaxis, both non-pharmacological and pharmacological, in a host of medical settings and there is sufficient evidence to support routine prophylaxis in many groups of patients. The implementation of decision making tools based on risk factor assessment improves the prescription of appropriate VTE prophylaxis. Nonetheless, thromboprophylaxis is often inadequate, with haphazard risk assessment and application of guidelines, leading to easily preventable instances of VTE. The most commonly used agents for pharmacological thromboprophylaxis of VTE are low dose unfractionated heparin; a low molecular weight heparin such as dalteparin, enoxaparin or tinzaparin; fondaparinux; warfarin; or aspirin. However, these have a number of drawbacks, principally the need for parenteral administration (with heparins) and frequent coagulation monitoring (with warfarin). The optimal anticoagulant would be orally administered, with a wide therapeutic window, rapid onset of action, predictable pharmacodynamics and pharmacokinetics, minimal interactions with food and other drugs, an ability to inhibit free and clot-bound coagulation factors, low, non-specific binding, and no requirement for routine coagulation monitoring or dose adjustment. A number of novel, single-target oral anticoagulants have been developed that appear to fulfill many of these requirements. This narrative review discusses the use of guidelines and risk assessment tools to identify patients at risk of VTE; it provides an overview of appropriate prophylaxis strategies in these patients with a summary of clinical trial results with novel oral anticoagulants.