Evolution of the Norwood procedure has culminated in there currently being three treatment strategies available for initial management: the ‘classical’ Norwood (utilizing a Blalock-Taussig shunt), the Norwood with right-ventricle to pulmonary artery (RV-PA) conduit, and the ‘hybrid’ Norwood procedure utilizing bilateral pulmonary artery banding and ductal stenting. Each variant has its potential advantages and disadvantages, and this paper looks to examine the evidence in favor of each strategy, with emphasis on the supportive data for the RV-PA conduit. The ‘classical’ procedure has the benefit of the greatest accumulated surgical experience and avoids any incision into the ventricle. However, the diastolic run-off of the Blalock-Taussig shunt can cause hemodynamic instability and unpredictable coronary steal phenomenon. The RV-PA conduit has the advantage of maintaining diastolic pressure with a more stable postoperative course, but at the cost of a ventriculotomy that may have detrimental long-term sequelae. The ‘hybrid’ procedure has the advantage of avoiding cardiopulmonary bypass, but does not always secure coronary blood flow and has a high inter-stage morbidity and reintervention rate. The evidence shows that each technique may have its place in future management, and that treatment algorithms could emerge that direct the choice of procedure for specific patient groups.
Introduction
In the field of congenital heart disease, no procedure has undergone greater scrutiny and debate more than the Norwood operation over the past 15 years. Constant refinements in technique and peri-operative management have led to a dramatic improvement in outcomes that, in turn, have had widespread influence in advancing neonatal surgery and intensive care. Early mortality for the procedure has fallen from 25% to 30% in the early 1990s to just 5% to 10% in many contemporary series.1, 2, 3 The reasons behind this improvement are many-fold and it can be difficult to measure the true benefit of each refinement amongst constantly re-engineered management strategies.
The most significant developments in the past decade have been the emergence of the right-ventricle to pulmonary artery (RV-PA) conduit as an alternative source of pulmonary blood supply to the Blalock-Taussig (BT) shunt, and the ‘Hybrid’ procedure of utilizing bilateral pulmonary artery banding and ductal stenting (Fig. 1).
Consequently, we are currently in a situation where three major treatment strategies co-exist: the ‘classical’ Norwood (utilizing a BT shunt), the RV-PA conduit, and the Hybrid procedure. This paper will discuss the evidence and rationale for each of these strategies, with a focus in the potential advantages of the RV-PA conduit, and will propose an algorithm for patient selection and operative strategy in hypoplastic left heart syndrome (HLHS).
Section snippets
The Rationale for the RV-PA Conduit
Throughout the 1980s and through to the early 2000s, the definitive technique for the Norwood procedure utilized a BT shunt as the source of pulmonary blood flow. During this period, the outcomes steadily improved as experience accumulated and advancements were characterized by shorter bypass times, the use of smaller shunt sizes, and better manipulation of Qp:Qs in the intensive care, particularly in the use of systemic vasodilatation.4, 5, 6 However, even by the late 1990s the operative
The Randomized Study: The Single Ventricle Reconstruction Trial
Prospective randomized trials are notoriously difficult to run in pediatric cardiac surgery, partly because of the number of cases necessary to stand up to meaningful statistical analysis. The Single Ventricle Reconstruction (SVR) trial, run by the Pediatric Heart Network Investigators in North America, has been an outstanding achievement and is one of the most remarkable triumphs of multi-center collaboration of the modern era.16 The trial successfully randomized 555 patients to either BT
Conventional Surgery Versus the Hybrid Procedure
The hybrid procedure has emerged over the past 10 years as an alternative to conventional surgery. It is an innovative concept that has the great advantage of avoiding cardio-pulmonary bypass, achieving a balanced circulation with bilateral pulmonary artery banding, atrial septostomy, and placement of a ductal stent (Fig. 1C). Comparison with conventional surgery is difficult because there is no Class I evidence and the procedure has generally been reserved for high-risk cases where the risks
Improvements in the RV-PA Conduits
There have been several proposed refinements to the RV-PA conduit technique that may further improve its outcomes.
Collating the Evidence: A Paradigm for the Management of HLHS
If a condition has three widely accepted operative techniques to treat it, then we can be certain that we have not yet found the perfect solution. Perhaps a less cynical interpretation would be to say that we need to recognize that HLHS forms a complex and highly variable spectrum, and that we now have the tools to apply different surgical approaches according to the specific morphology and physiology of the individual patient.
Despite the convincing evidence of the SVR trial, there remains
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