Perioperative Heparin Bridging in Patients With Mechanical Aortic Valves Undergoing Elective Surgery The AMBER Study

BACKGROUND: The benefit-risk balance of perioperative low-molecular-weight heparin (LMWH) bridging in patients with bileaflet mechanical aortic valves undergoing elective procedures is uncertain. While intended to prevent thromboembolism during warfarin interruption, LMWH may increase bleeding risk without a proven efficacy benefit. OBJECTIVES: This study aimed to evaluate the rates of thromboembolism and bleeding associated with different peri-operative LMWH bridging strategies compared to no bridging in this patient population. METHODS: In a multicenter retrospective cohort study, 553 patients requiring warfarin interruption were classified into 3 main analysis groups: preoperative and postoperative LMWH (n = 232), preoperative-only LMWH (n = 81), postoperative-only LMWH (n = 33), and no bridging (n = 207). The primary efficacy outcome was arterial thromboembolism within 30 days. Primary and secondary safety outcomes were major bleeding and clinically relevant non-major bleeding. Outcomes were analyzed with multivariable logistic regression and propensity-matched comparisons. RESULTS: Thromboembolic events were rare (<0.5%) and similar across all strategies. Compared to no bridging, full bridging was associated with significantly higher rates of major bleeding (3.0% vs 0%; P = 0.018) and any clinically relevant bleeding (9.5% vs 2.0%; P < 0.01). In multivariable models, full bridging predicted bleeding, whereas preoperative-only bridging did not. In a propensity-matched analysis, full bridging remained associated with a higher risk of any clinically relevant bleeding (10.6% vs 2.4%; P < 0.01). CONCLUSIONS: Among patients with bileaflet mechanical aortic valves undergoing elective procedures, 30-day thromboembolic events were rare. Full perioperative LMWH bridging was associated with increased bleeding. While this study provides valuable real-world data, prospective clinical trials are necessary to confirm and expand upon these findings.