Contemporary cardiac surgery outcomes databases: Data sources, variables, and applications.

Objective: Large-scale multicenter databases are foundational to observational research in cardiac surgery, enabling robust analysis of clinical outcomes, practice patterns, and population-level trends. We characterize the databases most frequently used in contemporary cardiac surgery outcomes research. Methods: We reviewed all retrospective observational studies published between January 2019 and August 2025 in 7 high-impact journals and identified 905 eligible articles utilizing 217 distinct databases. The 16 most frequently used databases were further evaluated on their specific characteristics including structure, patient coverage, clinical granularity, and follow-up. Results: The selected databases broadly included (1) clinical databases such as the Society of Thoracic Surgeons databases, European Registry for Patients with Mechanical Circulatory, and the Australia and New Zealand Fontan Registry; (2) administrative claims databases like Medicare Fee-for-Service and Taiwan's National Health Insurance Research Database; and (3) linkage-based sources such as the National Death Index. These databases varied in procedural detail, national coverage, follow-up, population score and data completeness. Conclusions: This study comprehensively characterized common contemporary large databases used in cardiac surgery outcomes research. A thorough understanding of databases, and how they align with specific research questions is essential to generating meaningful, generalizable clinical evidence to guide clinical practice.