Impact of age at Norwood surgery on pre–stage II outcomes in neonates with hypoplastic left heart syndrome

Objective:The timing of Norwood surgery, a potentially modifiable component of hypoplastic left heart syndrome management, lacks expert consensus, and its relationship to longer-term outcomes remains unclear. Methods:We performed a retrospective cohort study of neonates with hypoplastic left heart syndrome who underwent Norwood surgery between 2006 and 2023.The primary outcome was a composite of pre-stage II mortality or transplant and prolonged intensive care unit length of stay.The relationship between age at Norwood surgery and the composite outcome was assessed primarily through Cox proportional hazards analysis, modeling age as a restricted cubic spline, as a binary factor, and as a linear variable.Log-rank tests were used to compare subgroups based on age cutoffs determined from regression analysis. Results:In multivariable analysis with age modeled as restricted cubic spline, age at surgery (chi-square = 8.31, P = .0400),moderate or worse preoperative tricuspid regurgitation (chi-square = 3.94, P = .0472),and use of the valved Sano shunt compared with the Blalock-Taussig shunt ( = -1.1642,P = .0431)were independently associated with the composite outcome.When age at surgery was modeled as a binary variable, surgery on days 3 to 5 conferred a reduced risk compared with other days (hazard ratio, 0.53; 95% CI, 0.31-0.89;P = .0173).After day 4, a linear relationship is observed with a 34% increase in hazard per each additional day of age.Conclusions: Age at Norwood surgery is independently associated with pre-stage II outcomes.Surgery between days 3 and 5 may represent an optimal window for intervention, with delays in surgery beyond this period being associated with increased risk of adverse outcomes.(JTCVS Open 2025;:101550) 3 Hazard Ratio Age at Norwood (Days) Adjusted Hazard Ratio vs Age at Surgery 2 3 8 7 6 5 4 9 1 0 2 Visualization of the nonlinear relationship between age at Norwood surgery and adjusted HRs for the composite outcome of pre-stage II mortality, transplant, or prolonged ICU LOS, derived from a multivariable Cox proportional hazards model with age modeled as a restricted cubic spline. CENTRAL MESSAGEAge at Norwood surgery is independently associated with adverse outcomes.Days 3 to 5 of life may represent an optimal window for surgical intervention. PERSPECTIVEThis study expands on existing literature by further elucidating the relationship between age at Norwood surgery and clinical outcomes in neonates with HLHS.We found age at surgery to have a nonlinear relationship with the composite outcome of pre-stage II mortality/transplant or prolonged ICU LOS.A trough in hazard between age 3 and 5 days of life suggests a possible "golden window" for intervention.