Extended Venous Thromboembolism Prophylaxis After One-Anastomosis Gastric Bypass: A Three-Arm Randomized Trial of Enoxaparin Duration and Rivaroxaban.

backgroundVenous thromboembolism (VTE) is a serious but preventable complication after bariatric surgery, most of them after hospital discharge. The optimal regimen and duration of post-discharge prophylaxis, particularly the role of direct oral anticoagulants, remain uncertain.

objectivesTo estimate 30-day VTE and bleeding event rates in high-risk patients undergoing one-anastomosis gastric bypass who received 15-day enoxaparin, 30-day enoxaparin, or 30-day rivaroxaban prophylaxis, and to perform exploratory comparisons among the regimens.

methodsIn this randomized, open-label, three-arm clinical trial, high-risk adults undergoing laparoscopic OAGB were randomized before discharge (1:1:1) to enoxaparin 40 mg subcutaneously twice daily for 15 days, enoxaparin 40 mg twice daily for 30 days, or rivaroxaban 10 mg orally once daily for 30 days, after standardized in-hospital enoxaparin and early ambulation. Participants underwent clinical assessment and duplex ultrasonography of the lower-limb and porto-mesenteric veins on postoperative days 15 and 30. The primary outcome was objectively confirmed VTE within 30 days. Bleeding was classified as International Society on Thrombosis and Haemostasis (ISTH) major bleeding or clinically relevant non-major bleeding (CRNMB). Because the expected event rate was low and no non-inferiority or equivalence margin was prespecified, comparisons were interpreted as exploratory.

resultsA total of 288 patients were randomized to 15-day enoxaparin (n = 97), 30-day enoxaparin (n = 97), or 30-day rivaroxaban (n = 94). One symptomatic lower-limb deep vein thrombosis occurred in the 15-day enoxaparin group (1.0%; 95% CI, 0.03%-5.6%); no VTE events occurred in the 30-day enoxaparin group (0%; 95% CI, 0%-3.7%) or the rivaroxaban group (0%; 95% CI, 0%-3.8%). Total bleeding occurred in 4/97 patients (4.1%) in each enoxaparin group and 8/94 patients (8.5%) in the rivaroxaban group. The absolute difference in total bleeding between rivaroxaban and 30-day enoxaparin was 4.4% points (95% CI, - 2.9 to 12.2), indicating substantial imprecision. No porto-mesenteric venous thrombosis was detected.

conclusionOnly one VTE event occurred, precluding reliable conclusions regarding comparative efficacy or prophylaxis duration. Bleeding estimates were also imprecise and do not establish comparative safety or equivalence between rivaroxaban and enoxaparin. The trial adds descriptive event-rate data from a standardized OAGB pathway, but larger multicenter studies with prespecified comparative hypotheses and assessment of adherence, oral tolerance, and drug exposure are required. The study was approved by the Research Ethics Committee and registered at ClinicalTrials.gov.