Hybrid Alternatives To Norwood Stage-1 Are Not A Lower Risk Alternative: Norwood-Rvpa Offers Better Outcome In Comparable Neonates

Introduction: Hybrid strategies (HYBRID) for critical LVOTO have emerged as alternatives to stage-1 Norwood-BT shunt (BT) or Norwood-RV to PA conduit (RVPA) and may be pursued in neonates with unfavorable risk profile. An RCT determining the merit of HYBRID seems unlikely. We investigated the potential survival advantage of HYBRID strategies. Methods: In an inception cohort of neonates with critical LVOTO (2005-2014; 21 institutions) 564 had initial surgical palliation consisting of; stage-1 HYBRID (110; 20%), BT (232; 41%) or RVPA (222; 39%). Risk of death without Fontan/transplant was analyzed using risk-adjusted parametric competing risks models. Additional comparisons between HYBRID and BT/RVPA were made via propensity-matching using baseline morphologic and demographic variables. Results: At 6-years post stage-1, 49% and 8% had transitioned to Fontan and transplant respectively, 9% were alive without transition and 34% died; mortality plateaued at 3-years. Risk factors for death included small/atretic LVOT, small branch pulmonary arteries and low birth weight (BW). HYBRID was associated with a lower median BW (kg) than BT or RVPA (p Matched Comparison: Propensity matching resulted in 82 paired HYBRID/BT neonates (c-statistic=.77). Risk-adjusted 3-year mortality tended to be lower for HYBRID (32% vs. 40%, P=.28). Matching between HYBRID and RVPA resulted in 82 pairs (c-statistic=.75). Risk-adjusted mortality was significantly higher for HYBRID (42% vs. 25%; p=0.02). However, at low BW HYBRID had a survival advantage over RVPA at Conclusions: In neonates with critical LVOTO RVPA offers better survival to Fontan. Although baseline characteristics suggest an appropriate bias towards HYBRID in some higher risk neonates (e.g. low BW), HYBRID may not be lower risk alternative to Norwood in otherwise equivalent patients.