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

OBJECTIVES

Lifelong anticoagulation therapy is mandatory in patients with mechanical heart valves. The On-X aortic valve is currently the only mechanical heart valve approved for a lower (1.5-2.0) target international normalized ratio (INR) compared to the standard INR target 2.0-3.0. There is limited evidence demonstrating clinical benefits of the On-X valve over other mechanical aortic valves. We therefore investigated the risk of bleeding and thromboembolic events in patients with the On-X aortic valve.

METHODS

This nationwide, population-based cohort study, using the target trial emulation framework, included all adults who underwent primary mechanical aortic valve replacement in Sweden 2014-2022 from the SWEDEHEART register. The rates of major bleeding and thromboembolic events were obtained from national registers. Confounding was addressed by weighting.

RESULTS

Of the 3047 patients, 656 patients (22%) received an On-X aortic valve and 2391 patients (78%) received other mechanical aortic valves. The mean age was 54 years and 23% were women. After 8 years, the weighted major bleeding cumulative incidence was 7.2% (95% CI: 4.8%-10.7%) in the On-X valve group vs 7.0% (95% CI: 5.5%-8.8%) in the other mechanical valves group, and the weighted cumulative incidence of thromboembolic events was 7.3% (95% CI: 5.3%-10.2%) in the On-X valve group vs 6.4% (95% CI: 5.0%-7.9%) in the other mechanical valves group.

CONCLUSIONS

We found no clinically relevant difference in major bleeding or thromboembolic events in patients with the On-X aortic valve compared to patients with other mechanical aortic valves.