The Norwood operation represents one of the major milestones in pediatric cardiovascular surgery. Its development radically changed the natural history of hypoplastic left heart syndrome (HLHS) and other forms of single-ventricle physiology, transforming a condition that was virtually incompatible with neonatal survival into one associated with the possibility of prolonged life. This remarkable achievement has also changed the questions we need to ask. Once survival is no longer the sole objective, it becomes essential to understand how these patients live and how the disease affects their development, independence, and quality of life.
Against this background, Hill et al. reported the sixteen-year follow-up of the landmark Single Ventricle Reconstruction (SVR) trial, accompanied by an editorial by Winlaw et al. Although the original trial was designed to address a predominantly technical question, its long-term follow-up ultimately raises a much broader issue: whether the traditional criteria used to define success after the Norwood operation remain appropriate for a disease whose complexity accompanies patients throughout their lives.
Few controversies have had a comparable impact on congenital cardiac surgery. The SVR trial compared two different physiological strategies for providing pulmonary blood flow during neonatal reconstruction. The modified Blalock-Taussig-Thomas shunt (MBTTS), used for decades as the reference technique, supplies pulmonary blood flow from the systemic circulation. In contrast, the right ventricle-to-pulmonary artery shunt (RVPAS) provides antegrade flow from the right ventricle to the pulmonary arteries, aiming to improve early hemodynamic stability and reduce ventricular volume overload. The possibility that an apparently limited technical modification might alter the course of such a complex disease turned this comparison into one of the most relevant debates in contemporary congenital cardiology.
The initial publication of the trial appeared to provide a clear answer. The greater transplant-free survival observed during the first year among patients receiving an RVPAS led many centers to modify their clinical practice and was widely interpreted as a genuine paradigm shift in the Norwood operation.
Long-term follow-up has required that conclusion to be reconsidered. Sixteen years later, the early advantage of the RVPAS is no longer evident, and the overall analysis shows no significant differences between MBTTS and RVPAS when outcomes are assessed comprehensively. Rather than contradicting the original findings, this result illustrates an inherent feature of single-ventricle physiology: an advantage observed during one particular phase of the disease does not necessarily translate into a better clinical trajectory over the patient’s lifetime.
Perhaps the most important contribution of the study, however, is not the demonstration that both shunts ultimately provide comparable overall outcomes, but rather the recognition that the question guiding this debate for more than two decades may itself have been too narrow. For years, the objective was to determine which surgical strategy improved early survival. Today, an important portion of children survive that initial critical period, it has become clear that the real challenge lies elsewhere. Single-ventricle disease does not end after the Norwood operation; it continues to shape cardiovascular, neurological, and functional outcomes for decades. Assessing it exclusively through mortality or transplant-free survival captures only part of that reality.
Perhaps the problem was never simply determining which shunt was superior, but continuing to evaluate a lifelong disease using outcomes designed primarily to measure the first few months after surgery.
With this premise in mind, one of the study’s most innovative methodological features is its use of a global rank endpoint. This approach integrates and hierarchically ranks multiple clinical events according to their severity, assigning each patient a position within an overall spectrum of outcomes. Unlike traditional endpoints focused on a single event, the global rank endpoint simultaneously incorporates mortality, heart transplantation, and other major complications, while also considering ventricular function, lymphatic complications, neurodevelopment, adaptive functioning, and quality of life.
More than a statistical tool, the global rank endpoint represents a conceptual shift in how therapeutic success is interpreted. It acknowledges that the clinical course of these patients cannot be reduced to a single event and that single-ventricle disease must be understood as a chronic condition whose consequences extend far beyond survival. In this respect, the study shifts attention away from the success of an individual procedure and toward the patient’s overall life trajectory, a perspective that is far more consistent with the current challenges of congenital cardiology.
The results obtained with this approach are both revealing and clinically important. Approximately 87% of the cohort experienced death or at least one of the major adverse outcomes considered in the analysis, whereas only a small minority reached adolescence without experiencing any of these events. The figure is striking in itself, but its significance extends much further. Rather than simply quantifying a high burden of disease, it demonstrates that survival, although indispensable, is clearly insufficient to characterize the long-term course of these patients.
Many survivors continue to live with sequelae that profoundly influence their life trajectory yet remain invisible when therapeutic success is defined only as freedom from death or transplantation. Neurodevelopmental abnormalities, functional limitations, impaired adaptive functioning, ventricular dysfunction, and lymphatic complications are all part of a clinical reality that is rarely captured by conventional endpoints. From this perspective, the principal value of the global rank endpoint lies not only in its methodological sophistication, but also in providing an assessment that more closely reflects the real experience of patients and their families.
The study also conveys a particularly relevant clinical message. Whereas the pulmonary shunt strategy used during the Norwood operation no longer influenced overall long-term outcome, other factors remained associated with patient trajectory. Specifically, both prematurity and study site were independently associated with outcomes.
The association between prematurity and worse outcomes probably reflects greater biological vulnerability from birth, a phenomenon already described in other forms of complex congenital heart disease. The influence of study site is perhaps even more thought-provoking. Although the study cannot establish causal relationships or identify the mechanisms responsible, this finding broadens the focus of the discussion. Team experience, perioperative management, interstage surveillance, neurodevelopmental follow-up, multidisciplinary coordination, and access to specialized resources could all contribute to this variability.
In some ways, this finding shifts the discussion from surgical technique toward the broader model of care. If shunt type is no longer the main determinant of long-term prognosis, the next major improvement may depend less on further modifications of the Norwood operation and more on understanding which organizational characteristics allow some centers to achieve better outcomes. The question therefore evolves from “which technique should we perform?” to a potentially more important one: “which model of care provides these patients with the best clinical trajectory throughout their lives?”
Although the overall analysis identified no significant differences between MBTTS and RVPAS, the study did report an interesting finding in one subgroup analysis. Patients with moderate or severe tricuspid regurgitation appeared to have better outcomes when treated with an MBTTS. However, the small size of this subgroup requires cautious interpretation. This should be regarded as an exploratory, hypothesis-generating observation that does not, by itself, justify a change in clinical practice.
Nevertheless, this observation introduces a highly relevant concept for future research. The optimal surgical strategy may not be universal but instead may depend on specific anatomical and functional characteristics of each patient. If future studies confirm this hypothesis, the debate may shift away from identifying the single best shunt toward individualized selection of the most appropriate strategy for each clinical profile.
COMMENTARY:
The accompanying editorial probably provides the most compelling interpretation of these findings. Rather than viewing the absence of long-term differences between the two strategies as a failure of the Norwood operation, it suggests that this is the logical consequence of one of its greatest successes. By transforming a lethal disease into a condition compatible with prolonged survival, the procedure has created an entirely new set of challenges. Neonatal reconstruction is only the beginning of a care pathway that will extend over decades, and its ultimate outcome will depend not only on surgery but also on neurodevelopment, cardiovascular function, multidisciplinary care, family environment, and access to specialized resources.
This perspective represents a paradigm shift. For decades, research focused on refining surgical technique and reducing early mortality. The current challenge is to optimize the lifetime trajectory of these patients through care models capable of providing longitudinal, coordinated, patient-centered follow-up. Neurodevelopmental surveillance, rehabilitation, psychological support, early detection of complications, and structured transition to adult congenital heart disease programs are likely to become as important as the operation itself.
The principal merit of this study therefore lies not only in the answers it provides, but also in the questions it forces us to ask. For years, we debated which shunt was better. Sixteen years later, we now understand that although this debate was necessary, it was not sufficient. The real challenge is no longer simply to improve survival, but to improve the quality of that survival.
This may ultimately be the true legacy of the SVR trial: not the demonstration of definitive superiority of one technique over another, but a change in how success is defined in single-ventricle disease. Survival remains an extraordinary achievement and the essential foundation upon which everything else is built. Future progress, however, will no longer be measured solely by the number of years of life gained, but also by the quality of those years. If the past decades made it possible for these patients to live, the challenge for the decades ahead will be to help them live better.
REFERENCE:
Hill KD, Kang L, Wang Q, Newburger JW, Gaynor JW, Burns KM, et al. Single- ventricle disease: long-term outcomes and global morbidity in the Single Ventricle Reconstruction Trial. J Am Coll Cardiol. 2026;87(22):3114-3133. doi:10.1016/j.jacc.2026.01.049.
