Major Bleeding and Thromboembolic Events with the On-X Mechanical Aortic Valve Prosthesis: A SWEDEHEART Study

Area of Science:

• Cardiovascular Surgery
• Biomaterials Science
• Clinical Pharmacology

Background:

• Mechanical heart valves necessitate lifelong anticoagulation therapy.
• The On-X aortic valve is unique, approved for a lower target international normalized ratio (INR) of 1.5-2.0 compared to the standard 2.0-3.0.
• Limited evidence exists comparing the clinical benefits of the On-X valve against other mechanical aortic valves.

Purpose of the Study:

• To investigate the comparative risk of major bleeding and thromboembolic events in patients with the On-X aortic valve versus other mechanical aortic valves.
• To evaluate the safety and efficacy of the On-X aortic valve at a lower target INR in a real-world setting.

Main Methods:

• A nationwide, population-based cohort study using the target trial emulation framework.
• Inclusion of adult patients who underwent primary mechanical aortic valve replacement in Sweden between 2014 and 2022, sourced from the SWEDEHEART register.
• Analysis of major bleeding and thromboembolic event rates from national registers, with confounding addressed by weighting.

Main Results:

• The study included 3047 patients: 656 (22%) with On-X aortic valves and 2391 (78%) with other mechanical valves.
• After 8 years, weighted cumulative incidence of major bleeding was 7.2% for On-X vs. 7.0% for other valves.
• Weighted cumulative incidence of thromboembolic events was 7.3% for On-X vs. 6.4% for other valves.

Conclusions:

• No clinically significant differences in major bleeding or thromboembolic events were observed between the On-X aortic valve and other mechanical aortic valves.
• These findings suggest comparable safety profiles for the On-X valve at a lower INR target and other mechanical valves at standard INR targets.