Direct oral anticoagulants in deep vein thrombosis associated with inferior vena cava agenesis: A report of three cases and a systematic review.

Background: Inferior vena cava agenesis (IVCA) is a rare vascular abnormality characterised by the absence of one or more segments of the inferior vena cava and represents an underestimated cause of deep vein thrombosis (DVT). Given the very low prevalence of this condition and the lack of clinical trials, there is no consensus about the optimal anticoagulation strategy in IVCA-associated DVT. Objectives: To investigate efficacy and safety of direct oral anticoagulants (DOACs) in IVCA-associated DVT. Methods: We described three patients with IVCA-associated DVT followed at our Institution and treated with DOACs. Then, we performed a systematic review of the literature for ICVA-associated DVT treated with DOACs. Results: In addition to our 3 cases, we found data from 19 publications for a total of 30 patients with IVCA-associated DVT treated with DOACs (24 subjects treated with rivaroxaban, 8 with apixaban, and one with dabigatran). Most patients were males (72.7 %) with a median age at DVT onset of 26.0 years (min-max range 13-64 years). The majority of DVT events were unprovoked (76.0 %). The standard thrombophilia tests were mainly negative. The median follow-up period during DOAC therapy was 1.0 years (min-max range 0-10 years), with one recurrent splanchnic vein thrombosis reported and no haemorrhagic events. Conclusions: IVCA is a rare cause of DVT, which should be suspected in young adults with unprovoked DVT. Although future studies are needed, available data may support the use of DOACs in IVCA-associated DVT, with a reassuring profile of both efficacy and safety.