Comparison of Morbidity and Mortality Outcomes between Hybrid Palliation and Norwood Palliation Procedures for Hypoplastic Left Heart Syndrome: Meta-Analysis and Systematic Review

Background/Objectives: Hybrid palliation (HP) procedures for hypoplastic left heart syndrome (HLHS) are increasing. Our objective was to compare mortality and morbidity following HP and NP (Norwood palliation) procedures. Methods: Systematic review and meta-analysis of HLHS patients of peer-reviewed literature between 2000 and 2023. Mortality and/or heart transplantation in HP versus NP in the neonatal period, interstage period, and at 1, 3 and 5 years of age, and morbidity including completion of Stage II and Stage III palliation, unexpected interventions, pulmonary artery pressures, right ventricle function, neurodevelopmental outcomes and length of hospital stay were evaluated. Results: Twenty-one (meta-analysis: 16; qualitative synthesis: 5) studies evaluating 1182 HLHS patients included. HP patients had higher interstage mortality (RR = 1.61; 95% CI: 1.10–2.33; p = 0.01) and 1-year mortality (RR = 1.22; 95% CI: 1.03–1.43; p = 0.02) compared to NP patients without differences in 3- and 5-years mortality. HP procedure in high-risk HLHS patients had lower mortality (RR = 0.48; 95% CI: 0.27–0.87; p = 0.01) only in the neonatal period. HP patients underwent fewer Stage II (RR = 0.90; 95% CI: 0.81–1.00; p = 0.05) and Stage III palliation (RR = 0.78; 95% CI: 0.69–0.90; p < 0.01), had more unplanned interventions (RR = 3.38; 95% CI: 2.04–5.59; p < 0.01), and longer hospital stay after Stage I palliation (weighted mean difference = 12.88; 95% CI: 1.15–24.62; p = 0.03) compared to NP patients. Conclusions: Our study reveals that HP, compared to NP for HLHS, is associated with increased morbidity risk without an improved survival rate.