Direct oral anticoagulants versus vitamin k antagonists in patients with atrial fibrillation and bioprosthesis: a systematic review and meta-analysis
Authors: Guardia Martinez P , Aviles Toscano A L , Martinez Mayoral M A , Molto Miralles J 
Published: November 2023

Abstract

Background/Introduction
The large randomized clinical trials published to date have shown that direct oral anticoagulants (DOACs) are as or more effective than vitamin K antagonists (VKAs) in the prevention of thromboembolic events in atrial fibrillation (AF) and generally show a better bleeding risk profile. However, patients with bioprosthetic valves have been underrepresented in RCTs.
The aim of this study was to assess the safety and efficacy of DOAC in patients with AF and bioprosthetic valves through a systematic review and meta-analysis including recent evidence from comparative cohort studies and real-world results.

Methods
A systematic review of the scientific literature and a subsequent meta-analysis were carried out.
We included RCTs or comparative observational studies, published from January 2017 to January 2022 comparing DOACs versus vitamin K antagonists in patients with AF or atrial flutter and bioprostheses.
We collected data of all-cause mortality, major bleeding, and systemic embolism.
The primary outcome of interest was all-cause mortality. Secondary outcomes were systemic embolism or stroke. The primary safety outcome was major bleeding.

Results
Our analysis included 12 studies, 4 RCTs and 8 observational studies that enrolled a total of 30.283 patients.
All-cause mortality
6 observational and 3 RCT were combined. A 9% reduction was found for all-cause mortality in patients treated with DOACs (HR,0.91; P=.0068;95%CI,0.85–0.97;I2=8%).
Stroke and systemic embolism
4 RCT and 8 observational studies were combined. No evidence showing a significant effect of DOAC therapy on risk reduction for stroke and embolism was obtained (HR, 0.87; P =.29; 95%CI, 0.67–1.14; I2=45%).
Major bleeding
The results of the 12 studies were combined. A robustness analysis was performed, and the ENVISAGE RCT was identified as atypical. We therefore proceeded to re-run the meta-analysis without this study’s results. The overall effect size was HR, 0.79 (P = .0001; 95%CI, 0.73-0.85; I2 = 0%), with a 21.1% reduction of major bleeding with DOAC therapy compared with VKA.
The present study has several limitations. It has the inherent limitations of the studies included and the combination of findings from comparative observational cohort studies and ad hoc studies from RCTs, which entails a potential source of bias. Second, individual risks for each type of bioprosthesis were not studied. Finally, the four currently marketed DOACs were included in our meta-analysis, but their efficacy and safety were not evaluated separately.

Conclusions
Our study found that DOAC therapy is associated with a significant reduction of all-cause mortality with no significant increase in the risk of systemic embolism or stroke. This reduction could be attributed to a decrease in major bleeding. Our results therefore suggest that DOACs could be a safer alternative than VKAs in this group of patients.