Callahan CP, Miller P, Carvajal H, Wan F, Canter M, Mannie C, Hill GD, Eghtesady P. Hybrid vs. Norwood: An Analysis of the NPC-QIC Database to Determine Optimal Approach for High-Risk Single Ventricle Patients. Pediatric Cardiology. 2026. doi:10.1007/s00246-026-04166-7.
PubMed: https://pubmed.ncbi.nlm.nih.gov/41579199/
Take-Home Points
- Among 398 high-risk (patients with birth weight ≤ 2.5 kg or gestation ≤ 35 weeks, and age ≤ 30 days at admission were included) single-ventricle neonates from 57 centers, primary Norwood palliation was associated with superior one-year survival compared with hybrid strategies.
- One-year survival was 70% after Norwood, compared with 54% after surgical hybrid palliation and 55% after pulmonary artery banding with prostaglandin infusion (PAB/PGE).
- Stage 2 completion rates were significantly higher after Norwood (90%) than after hybrid (61%) or PAB/PGE (67%) management.
- The survival advantage of Norwood disappeared in infants weighing ≤2.12 kg at birth, where one-year survival was similarly poor regardless of strategy.
- Genetic abnormalities, post-stage I ECMO support, and hybrid strategy were independently associated with worse outcomes.
- Infants with birth weight ≤2.12 kg combined with genetic abnormalities represented an exceptionally high-risk group, with fewer than 25% surviving and reaching Stage 2 palliation during follow-up.
Commentary from Dr. Varun Aggarwal (Wilmington, DE, USA), editor-in-chief of Congenital Heart Disease Journal Watch:
Few questions in congenital heart surgery are more difficult than determining the optimal management strategy for the fragile neonate with hypoplastic left heart syndrome (HLHS) or related single-ventricle anatomy who is born too small, too premature, or too medically complex for conventional pathways to feel comfortable. While the Norwood operation remains the standard first-stage palliation for most infants with HLHS, clinicians have long searched for alternative approaches that might reduce risk in the most vulnerable patients. Hybrid strategies, which seek to avoid neonatal cardiopulmonary bypass by combining pulmonary artery banding with ductal maintenance, have emerged as an attractive concept. Yet after nearly two decades of experience, uncertainty persists regarding which patients truly benefit.
This study provides one of the largest contemporary evaluations of that question. Drawing from the National Pediatric Cardiology Quality Improvement Collaborative (NPC-QIC), the investigators analyzed 398 high-risk single-ventricle infants from 57 centers. High risk was defined pragmatically as birth weight ≤2.5 kg or gestational age ≤35 weeks, two of the most powerful predictors of adverse outcomes throughout congenital heart surgery. The resulting cohort reflects the exact population that often generates the greatest debate in multidisciplinary conferences and family counseling sessions.
The headline finding is straightforward: among high-risk single-ventricle infants overall, the Norwood operation was associated with superior one-year survival and significantly greater progression to Stage 2 palliation. Survival reached 70% in the Norwood group compared with approximately 55% among hybrid and PAB/PGE patients. Likewise, 90% of Norwood survivors progressed to Stage 2 palliation compared with 61% and 67% in the hybrid groups. These differences are difficult to ignore.
At first glance, these findings appear to challenge the rationale behind hybrid palliation. If avoiding bypass and circulatory arrest does not improve survival, why should hybrid strategies remain attractive?
The answer is that patient selection still matters enormously.
Patients undergoing hybrid palliation in this study were not equivalent to those undergoing Norwood. They had lower birth weight, younger gestational age, and substantially higher rates of chromosomal and extracardiac abnormalities. In other words, clinicians were already using hybrid strategies for the infants they perceived to be at highest risk. Therefore, the poorer outcomes observed after hybrid palliation likely reflect, at least in part, the increased vulnerability of those patients rather than an inherent inferiority of the strategy itself.
The most important contribution of this study may therefore be its subgroup analysis. When investigators examined the smallest infants, those weighing ≤2.12 kg at birth, the survival advantage of Norwood disappeared. One-year survival fell to approximately 56% to 59% regardless of whether patients underwent Norwood, surgical hybrid palliation, or PAB/PGE. This observation suggests that there may be a threshold below which the biology of extreme prematurity and low birth weight overwhelms the benefits of any particular surgical approach.
The implications of this finding are profound. For years, debates have focused on whether Norwood or hybrid palliation is superior for the highest-risk infants. This study raises the possibility that the more relevant question may be whether either strategy meaningfully alters prognosis in the most vulnerable subgroups. When survival remains poor across all approaches, the conversation shifts from selecting the optimal operation to understanding the limits of current therapy.
The study also provides important insight into predictors of outcome. Genetic abnormalities increased mortality risk and reduced progression to Stage 2 palliation. Postoperative ECMO emerged as one of the strongest markers of adverse outcome, increasing mortality risk more than sevenfold. These findings align with longstanding observations that outcomes in single-ventricle palliation are strongly influenced by factors extending beyond cardiovascular anatomy alone. Prematurity, genetics, end-organ function, and perioperative instability remain major determinants of success.
Particularly interesting is the experience with PAB/PGE. More than 80% of infants managed initially with pulmonary artery banding and prostaglandin infusion eventually underwent a delayed Norwood procedure. Furthermore, those who successfully progressed to delayed Norwood demonstrated substantially better survival than those who did not. This supports the concept of pulmonary artery banding as a bridge-to-decision strategy rather than a definitive pathway. In some patients, time itself may function as a therapeutic intervention, allowing somatic growth, stabilization, and refinement of risk before undertaking definitive reconstruction.
For congenital heart surgeons, the findings reinforce a difficult reality. High-risk HLHS remains one of the greatest challenges in pediatric cardiovascular medicine. Despite advances in perioperative care, interstage monitoring, surgical technique, and hybrid technologies, outcomes remain substantially worse than those seen in standard-risk single-ventricle populations. Even among the best-performing pathway in this study, nearly one-third of high-risk infants failed to survive the first year.
The discussion regarding futility is perhaps the most courageous aspect of the manuscript. The authors explicitly sought to identify patient subsets in whom intervention may offer very limited benefit. While no definitive threshold emerged, the combination of extreme low birth weight and genetic abnormalities identified a population with extraordinarily poor outcomes. The authors appropriately stop short of recommending comfort care based on any single variable but highlight the need for transparent family counseling grounded in realistic expectations.
Importantly, these data should not be interpreted as evidence that hybrid palliation lacks value. Hybrid approaches remain indispensable in many centers and may provide the only feasible pathway for extremely unstable patients. Rather, the lesson is that hybrid palliation should be viewed as a strategy to address specific physiologic challenges rather than as a universally superior rescue approach for all high-risk patients.
Ultimately, this study suggests that Norwood remains the benchmark against which alternative strategies should be measured. For most high-risk single-ventricle infants, primary Norwood was associated with the best survival and greatest likelihood of reaching Stage 2 palliation. However, the data also remind us that some infants remain at extraordinarily high risk regardless of operative strategy. For those patients, the next advances in care may come not from choosing a different operation but from developing entirely new approaches to risk modification, prenatal optimization, and myocardial support.
Clinical Perspective
Among contemporary high-risk single-ventricle infants, primary Norwood palliation was associated with superior one-year survival and greater progression to Stage 2 reconstruction compared with hybrid strategies. However, in infants weighing ≤2.12 kg at birth, this advantage disappeared, suggesting that extreme low birth weight may define a population in whom current surgical strategies provide similarly limited outcomes. Careful patient selection, comprehensive counseling, and individualized decision-making remain central to management of this challenging population.
