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Low-Dose vs Standard Warfarin After Mechanical Mitral Valve Replacement: A Randomized Trial
Michael W A Chu1, Marc Ruel2, Allen Graeve3
1London Health Sciences Centre, Western University, London, Ontario, Canada.
The Annals of Thoracic Surgery
|January 7, 2023
Summary
Low-dose warfarin (target INR 2.0-2.5) did not prove noninferior to standard-dose warfarin (target INR 2.5-3.5) for On-X mechanical mitral valves. The composite event rate was similar, but noninferiority was not met.
Area of Science:
- Cardiology
- Biomedical Engineering
- Clinical Trials
Background:
- Current guidelines recommend a target INR of 2.5-3.5 for mechanical mitral prostheses.
- The PROACT trial investigated lower warfarin doses for On-X mechanical mitral valves.
Purpose of the Study:
- To assess the safety and efficacy of low-dose warfarin compared to standard-dose warfarin in patients with On-X mechanical mitral valves.
- To determine if a lower target INR range is noninferior to the current standard.
Main Methods:
- 401 patients with On-X mechanical mitral valves were randomized to low-dose (INR 2.0-2.5) or standard-dose (INR 2.5-3.5) warfarin.
- All patients received aspirin 81 mg daily, with encouragement for home INR monitoring.
- The primary endpoint was the combined rate of thromboembolism, valve thrombosis, and bleeding events.
Main Results:
- Mean follow-up was 4.1 years, with mean INRs of 2.47 (low-dose) and 2.92 (standard-dose).
- The primary endpoint event rates were 11.9%/year (low-dose) and 12.0%/year (standard-dose), failing to meet the noninferiority margin.
- Individual event rates for thromboembolism, valve thrombosis, and bleeding were similar between groups.
Conclusions:
- Low-dose warfarin did not achieve noninferiority compared to standard-dose warfarin for the composite endpoint in patients with On-X mechanical mitral valves.
- Further research may be needed to optimize anticoagulation strategies for specific mechanical valve types.
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