BACKGROUNDDisparities in congenital heart disease care exist between high-income and low- and middle-income countries (LMICs), likely extending to congenital cardiac catheterization (CCC).OBJECTIVESThis study compares patient characteristics and outcomes of CCC in the U.S.-based Congenital Cardiac Catheterization Project on Outcomes (C3PO) and the International Quality Improvement Collaborative-Congenital Heart Disease Catheterization Registry (IQIC-CHDCR) from LMICs.METHODSThe analysis included all CCC procedures recorded in C3PO (19 sites) and IQIC-CHDCR (19 sites) from 2019 to 2022. Patient and procedural characteristics, resource utilization, and outcomes were compared.RESULTSA total of 28,957 C3PO and 6,485 IQIC-CHDCR cases were analyzed. Single ventricle patients accounted for 30% of C3PO and 13% of International Quality Improvement Collaborative (IQIC), with high-risk procedures (procedural risk in congenital cardiac catheterization 3-5) performed more frequently in C3PO (42% vs 23%). Median procedure duration was longer in C3PO (1.5 vs 0.8 hours). Clinically meaningful adverse event (CMAE) rates were higher in C3PO (3.9% vs 1.5%), though mortality was comparable (0.5% vs 0.7%). Risk-adjusted analysis showed a lower ratio in IQIC for both CMAE (0.50; 95% CI: 0.39-0.62) and severity level 4/5 events (0.71; 95% CI: 0.52-0.96). However, failure-to-rescue rates were higher in IQIC (7.1% vs 2.1%).CONCLUSIONSThe harmonized databases facilitated direct comparison of CCC practices, revealing more complex patients and resource-intensive procedures in C3PO, while the IQIC cohort demonstrated lower CMAE rates but a slightly higher mortality rate. These findings emphasize the need for further risk adjustment modeling for LMICs and identify areas to enhance global resource access and patient outcomes.