Extended thromboprophylaxis in the acutely ill medical patient after hospitalization - a paradigm shift in post-discharge thromboprophylaxis.

Venous thromboembolism (VTE) is a significant healthcare burden with approximately 900,000 events annually in the United States, over half of which are healthcare-associated. This number is anticipated to double by 2050. Group prophylaxis strategies confined to the inpatient setting appear to have minimal impact on the reduction of post-discharge VTE in medically ill patients due to shortened lengths of stay and a heterogenous population that includes patients at low risk for VTE. In accordance with current guideline recommendations, very few (<5%) medically ill patients are discharged with extended prophylaxis, which potentially creates a clinical gap for at-risk patients as VTE risk has been shown to persist for up to 90 days. Initial studies of extended thromboprophylaxis in acutely ill medical patients with enoxaparin, rivaroxaban and apixaban showed little to no benefit towards VTE reduction that was consistently outweighed by increased bleeding. The more recent APEX study that compared betrixaban to enoxaparin in an enriched patient population at high-risk for VTE was the first study of extended thromboprophylaxis that showed similar efficacy in VTE prevention without an increase in major bleeding. Based on the APEX results, betrixaban recently gained FDA approval for extended thromboprophylaxis in acutely ill medical patients. Recognition that up to half of medically ill patients are not at sufficient risk to warrant thromboprophylaxis has driven extensive research towards development of scientifically derived and validated VTE risk assessment models intended to identify patients who do not warrant prophylaxis, as well as those at high risk who may derive benefit from extended thromboprophylaxis. This article will review prior and ongoing extended thromboprophylaxis studies, VTE and bleed risk assessment models, incorporation of biomarkers in VTE risk assessment and key issues in the paradigm shift towards individualized VTE prophylaxis in acutely ill medical patients.