Anticoagulation After Bioprosthetic Aortic Valve Replacement
What is the safety and efficacy of anticoagulation following bioprosthetic aortic valve replacement using a meta-analysis of available studies?
A total of 13 studies were identified, which evaluated either no therapy/aspirin or anticoagulation with Coumadin in patients who had undergone bioprosthetic aortic valve replacement. The outcomes in all analyzed studies included venous thromboembolism, stroke, transient ischemic attack, and bleeding events. Within the 13 studies, there were 6,431 cases and 18,210 controls (controls included those on aspirin or no therapy). Results were assessed at 3 months and overall. Duration of therapy was 3 months in 8 of 13 studies, and varied from 1-24 months in the others.
Compared to aspirin or no therapy, anticoagulation was associated with an increased frequency of overall bleeding (odds ratio [OR], 1.38; p = 0.013) and a trend toward increased bleeding risk at 3 months (OR, 1.26; p = 0.084). There was no difference at 3 months in the rate of the composite primary endpoint (venous thromboembolism, stroke, or transient ischemic attack) (OR, 1.01; p = 0.967). For the time interval >3 months, anticoagulation was not shown to improve outcomes (OR, 1.08; p = 0.78).
A meta-analysis of available studies suggests that anticoagulation significantly increased bleeding risk without having a favorable effect on thromboembolic events in patients receiving a bioprosthetic aortic valve replacement.
Current American College of Cardiology/American Heart Association guidelines recommend 3 months of anticoagulation after bioprosthetic aortic valve replacement in an effort to reduce thromboembolic complications (Class IIb, Level of Evidence B). Thromboembolic events are theorized to occur related to formation of thrombus on the freshly implanted bioprosthetic valve. It is also hypothesized that after 3 months, the valve ring has become endothelialized and the risk of embolic events is negligible. This meta-analysis suggests that there may be no clinical benefit to anticoagulation following bioprosthetic aortic valve replacement, either in the short-term (3 months) or longer-term, and furthermore, anticoagulation increases bleeding complications.
As the authors appropriately point out, the studies incorporated in this meta-analysis are largely observational and many do not fully report patient specifics, which may have contributed to either beneficial outcomes or any increased likelihood of complications. Selection bias and variable management strategies also weaken the strength of the included studies. Furthermore, data regarding the degree of compliance and adherence to international normalized ratio targets were not available. Nevertheless, this study does raise concern that in the general population, use of anticoagulation following bioprosthetic aortic valve replacement may not be necessary and may result in increased bleeding complications. Obviously, a large-scale randomized trial of anticoagulation in this setting would be beneficial.
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