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Lower warfarin dose feasible after surgical AVR with mechanical valve
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Among patients who underwent surgical aortic valve replacement with a mechanical valve designed to be used with reduced anticoagulation therapy, reduced warfarin intensity did not lead to increased thrombotic risk, researchers reported.
However, using dual antiplatelet therapy instead of anticoagulants after surgical AVR was associated with elevated risk for thromboembolism and valve thrombosis.
For the PROACT trial, the researchers randomly assigned 201 low-risk patients undergoing surgical AVR with the mechanical valve (On-X, On-X Life Technologies) to DAPT (clopidogrel plus aspirin) or standard warfarin (INR, 2 to 3) plus aspirin 3 months after the procedure, and they randomly assigned 375 patients with at least one thromboembolic risk factor undergoing surgical AVR with the mechanical valve to lower-intensity warfarin (INR, 1.5 to 2) plus aspirin or standard warfarin plus aspirin 3 months after the procedure. Between the procedure and 3 months, all patients received standard warfarin plus aspirin.
At 8.8 years of follow-up, the low-risk arm of the study was terminated due to excess cerebral thromboembolic events in the DAPT group (3.12% per patient-year vs. 0.29% per patient-year; P = .02), John D. Puskas, MD, MSc, from Icahn School of Medicine at Mount Sinai, and colleagues wrote, noting there was no difference between the groups in bleeding or all-cause mortality.
In the high-risk arm, at 8.7 years, those assigned lower-intensity warfarin had lower rates of major bleeding (1.59% per patient-year vs. 3.94% per patient-year; P = .002) and minor bleeding (1.27% per patient-year vs. 3.49% per patient-year; P = .002), with no differences in thromboembolism (P = .2) or all-cause mortality, the researchers wrote.
“These findings led the FDA to support an indication for use for the On-X valve in the aortic
position with an INR of 1.5 to 2.0 plus 81 mg of aspirin after 3 postoperative months of standard warfarin therapy and aspirin 81 mg per day,” Puskas and colleagues wrote.
In a related editorial, Richard P. Whitlock, MD, PhD, from Population Health Research Institute, Hamilton, Ontario, Canada, and colleagues wrote: “The results clearly indicate that dual antiplatelet therapy is not a viable alternative to anticoagulation for patients with mechanical aortic valves and suggest that newer-generation bileaflet mechanical valves in the aortic position warrant less intense anticoagulation than is currently recommended.” – by Erik Swain
Disclosures: The study was funded by On-X Life Technologies. Puskas reports no relevant financial disclosures. Whitlock reports he receives consultant fees and speaker honoraria from Armetheon, Boehringer Ingelheim and Novartis. Please see the study and editorial for all the other authors’ relevant financial disclosures.
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