A meta-analysis of previous studies reveals that anticoagulation in aortic bioprosthesis significantly increases bleeding risk and did not reduce the risk of clinical thromboembolic events. Findings of the analysis were published in Circulation: Cardiovascular Quality and Outcomes.

The American College of Cardiology guidelines currently recommend 3 months of anticoagulation therapy after aortic valve replacement with a bioprosthesis. However, previous clinical studies have shown conflicting results, prompting researchers to assess bleeding risk and improved outcomes with anticoagulation in the setting of a new bioprosthesis via meta-analysis.

“The perioperative period is a well-known hypercoagulable milieu, and the risk of thromboembolism in these patients rapidly declines over time,” the study authors wrote. “As such, any benefit from anticoagulation would likely be seen very early after surgery.”


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“It is further important to recognize that the highest risk for thrombi occurs during a period (within the first 24 to 48 hours) when anticoagulant use is generally prohibited because of the risk for incisional bleeding, an event that is strongly linked to perioperative morbidity and mortality.”

The investigators identified observational studies or clinical trials via the PubMed database through April 2015 that assessed anticoagulation with warfarin compared with either aspirin or no antiplatelet or anticoagulant therapy. They selected studies that had thromboembolism or stroke ischemic attacks and bleeding events included in their outcome data.

They also performed quality assessment in accordance with the Newland Ottawa Scale, used random effects analysis to pool the data from the available studies, and conducted I2 testing to assess heterogeneity in the studies. A total of 170 articles were screened, and 13 studies (6431 cases; 18 210 controls) were included in the final analysis.

Warfarin use was associated with significantly increased risk of overall bleeding (odds ratio [OR]: 1.96; 95% confidence interval [CI]: 1.25-3.08; P<.0001) and bleeding risk at 3 months (OR: 1.92; 95% CI: 1.10-3.34; P<.0001) compared with aspirin or placebo.

Researchers saw no significant difference with warfarin use regarding composite primary outcome variables—risk of venous thromboembolism, stroke, or transient ischemic attack (OR: 1.13; 95% CI: 0.82-1.56; P=0.67). They also observed that anticoagulation did not improve outcomes after more than 3 months (OR: 1.12; 95% CI: 0.80-1.58; P=.79).

The authors noted that it is currently unknown whether these findings would be applicable to patients undergoing transcatheter aortic valve replacement (TAVR).

“The best manner in which to determine the value of anticoagulation in these [TAVR] patients and patients with surgical AVR would be with a randomized controlled trial that would ideally be triple armed (antiplatelet vs anticoagulant vs placebo),” they explained. “Until that time, our analysis suggests that anticoagulation of bioprosthetic valves in the absence of other indications for thrombosis prevention seems to be a dangerous practice.”

Reference

Riaz H, Alansari SAR, Khan MS, et al. Safety and use of anticoagulation after aortic valve replacement with bioprostheses: A meta-analysis. Circ Cardiovasc Qual Outcomes. 2016; doi: 10.1161/circoutcomes.115.002696.