Anticoagulation for Pregnant Individuals With Mechanical Heart Valves: A Methodologic Review of Systematic Reviews

In this study we aimed to describe methodologic variations in systematic reviews (SRs) that estimated clinical outcomes with different anticoagulant strategies for pregnant individuals with mechanical heart valves (MHVs), and present the most reliable risk estimates. We identified eligible SRs through a search involving 8 databases and critically appraised: 1) study quality using A MeaSurement Tool to Assess systematic Reviews (AMSTAR 2); 2) search strategies using Peer Review of Electronic Search Strategies (PRESS) guidelines and operationalized criteria of SR searches; and 3) meta-analytic approaches using a self-designed checklist. We determined most reliable estimates for clinical outcomes using an algorithm considering AMSTAR 2 scores, quality of search strategy, and recency of publication. Of the 12 eligible SRs, most (9 of 12) were of critically low quality based on AMSTAR 2. Of the 4 SRs that published search strategies, 3 were of low quality based on PRESS guidelines. Meta-analytic approaches varied widely. The most reliable risk estimates with vitamin K antagonists were 0.9% (95% confidence interval [CI] 0.1%-1.6%) for maternal mortality, 2.7% (1.4%-4.0%) for thromboembolism, 35.5% (19.8%-51.2%) for fetal loss, and 2.0% (0.3%-3.7%) for congenital anomalies. These risks with sequential therapy were 2.0% (0.8%-3.1%), 5.8% (3.8%-7.7%), 20.1% (14.4%-25.7%), and 1.4% (0.3%-2.5%), and with low-molecular-weight heparin they were 2.9% (0.2%-5.7%), 8.7% (3.9%-13.4%), 8.0% (2.0%-13.9%), and 0.0% (0.0), respectively. SRs on anticoagulation for pregnant individuals with MHVs demonstrated considerable heterogeneity in terms of study quality, search strategies, and meta-analytical approaches. The risk estimates provided could inform shared decision-making and clinical practice guidelines.