Objectives: To assess if warfarin targeted to INR 1.8 (range 1.5-2.0) is safe for all patients with an On-X aortic mechanical valve.
Methods: This prospective, observational registry follows patients receiving warfarin targeted at an INR of 1.8 (range 1.5-2.0) plus daily aspirin (75-100 mg) after On-X aortic valve replacement. The primary end-point is a composite of thromboembolism, valve thrombosis, and major bleeding. Secondary end-points include the individual rates of thromboembolism, valve thrombosis, and major bleeding, as well as the composite in subgroups of home or clinic-monitored INR and risk categorization for thromboembolism. The control was the patient group randomized to standard-dose warfarin (INR 2.0-3.0) plus daily aspirin 81 mg from the PROACT trial.
Results: A total of 510 patients were enrolled at 23 centers in the UK, United States, and Canada. Currently, the median follow-up duration is 3.4 years, and median achieved INR is 1.9. The primary composite end-point rate in the low INR patients is 2.31% vs 5.39% (95% confidence interval 4.12%-6.93%) per patient-year in the PROACT control group, constituting a 57% reduction. Results are consistent in subgroups of home or clinic-monitored, and high-risk patients, with reductions of 56%, 57%, and 57%, respectively. Major and total bleeding are decreased by 85% and 73%, respectively, with similar rates of thromboembolic events. No valve thrombosis occurred.
Conclusions: Interim results suggest that warfarin targeted at an INR of 1.8 (range 1.5-2.0) plus aspirin is safe and effective in patients with an On-X aortic mechanical valve with or without home INR monitoring.
Keywords: On-X valve; anticoagulation; aortic valve replacement; low-dose warfarin; mechanical heart valve; prosthetic valve.
© The Author(s) 2024. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery.