Endothermal heat-induced thrombosis (EHIT) is a thrombotic complication specific to endovenous thermal ablation of the great saphenous vein (GSV), for which no prophylactic regimen is standardized. This single-centre, single-operator randomized trial compared a brief 5-day post-procedural course of the direct oral anticoagulants apixaban and rivaroxaban against no anticoagulation for the prevention of EHIT after GSV endovenous laser ablation performed with concurrent below-knee foam sclerotherapy. Treated limbs were randomly allocated 2:1:1 (no anticoagulant : rivaroxaban : apixaban), and EHIT was graded on post-ablation duplex by the American Venous Forum (AVF) classification.

The unit of randomization was the treated limb, assigned by a computer-generated random sequence. Some participants underwent bilateral procedures and could contribute limbs to different arms; within-participant correlation was addressed with patient-clustered robust standard errors and a one-limb-per-patient sensitivity analysis. The primary endpoint was clinically significant (AVF class ≥II) EHIT on the first post-ablation duplex, which was performed and interpreted by two registered vascular technologists blinded to treatment allocation, with adjudication by the treating physician.

Inclusion Criteria:

Adults aged 18 years or older Undergoing great saphenous vein endovenous laser ablation for symptomatic reflux Concurrent below-knee foam sclerotherapy

Exclusion Criteria:

Known thrombophilia Current oestrogen or hormone-replacement therapy Family history of venous thromboembolism or thrombophilia Active malignancy Prior ipsilateral ablation Deep venous reflux or obstruction

Who is masked: Outcomes Assessor (duplex read by blinded technologists)