Assessing the applicability of Society of Thoracic Surgeons-European Association for Cardio-Thoracic Surgery (STAT) categories in neonatal and low-weight congenital cardiac surgery: Insights from 20 years at a single center.

OBJECTIVE: The Society of Thoracic Surgeons-European Association for Cardio-Thoracic Surgery (STAT) Mortality Categories were developed from large multicenter databases to stratify surgical risk in congenital heart surgery. However, their predictive validity in high-risk subgroups such as neonates and infants of low birth weight, especially in small- to medium-volume centers, remains unclear. METHODS: We retrospectively analyzed all congenital cardiac surgeries performed at our center between 2005 and 2025. We assessed 30-day mortality by STAT category in the overall cohort and in prespecified subgroups: neonates (<31 days), non-neonates (≥31 days), and low birth weight (<2.5 kg). We performed correlation analyses and multivariable logistic regression models with interaction terms (STAT × neonate, STAT × low weight). RESULTS: Among 4768 operations, 1257 (26.3%) were in neonates and 191 (4.0%) in patients <2.5 kg. Overall mortality increased progressively with STAT category (1: 1.1%, 2: 3.7%, 3: 5.8%, 4: 12.8%, 5: 26.7%). Neonates exhibited greater mortality across all STAT levels, including categories considered low risk in older children (STAT 1: 9%, STAT 2: 6%). Logistic regression showed that STAT was a strong predictor of mortality (odds ratio [OR], 2.26; 95% CI, 1.94-2.64), whereas neonates had a greater baseline risk (OR, 3.88; 95% CI, 1.60-9.40); however, the STAT × neonate interaction suggested attenuated predictive performance in neonates (OR, 0.80; 95% CI, 0.63-1.01). CONCLUSIONS: STAT categories were associated with mortality overall but demonstrated attenuated discrimination in neonates, highlighting the limitations of procedure-only stratification in physiology-dominated subgroups.