Norwood Procedure — How It Works, Benefits & Recovery — Procedure Guide, Recovery & Risks | MyMedicPlus

The Norwood procedure is the first-stage surgical palliation for hypoplastic left heart syndrome (HLHS) and functionally equivalent single-ventricle congenital cardiac defects. HLHS is a spectrum of severe congenital anomalies characterised by hypoplasia (underdevelopment) of the left ventricle, mitral valve, aortic valve, and ascending aorta, rendering the left ventricle incapable of sustaining systemic circulation. Without intervention HLHS is universally fatal within days of birth when the ductus arteriosus closes. The Norwood procedure — first performed by William Norwood in 1979 with the first successful series reported in the NEJM in 1983 — is a complex open-heart operation performed on neonates in the first week of life on cardiopulmonary bypass with deep hypothermic circulatory arrest (DHCA). Its three principal goals are: (1) creating an unobstructed connection between the single functioning right ventricle and the systemic circulation via a reconstructed 'neo-aorta' that incorporates the patient's own pulmonary trunk; (2) establishing controlled pulmonary blood flow sufficient for oxygenation but not causing pulmonary over-circulation via a systemic-to-pulmonary shunt or right ventricle-to-pulmonary artery conduit; and (3) creating an unrestrictive interatrial communication (atrial septectomy) to ensure unrestricted mixing of oxygenated and deoxygenated blood at atrial level. The Norwood is the first of three staged palliative operations; it is followed by the bidirectional Glenn procedure at 4–6 months (Stage II) and the Fontan completion at 2–4 years (Stage III), which progressively separate pulmonary and systemic circulations.

The Norwood procedure is performed on neonates with HLHS or functionally equivalent single-ventricle defects where the left ventricle cannot support systemic circulation. HLHS affects approximately 1 in 3,400 live births, accounting for 2–3% of all congenital heart defects, and is the most common cause of cardiac death in the first week of life. Variants amenable to Norwood palliation include aortic atresia with mitral atresia (AAMD), aortic atresia with mitral stenosis (AAMS), and severe aortic stenosis with a small left ventricle. Prenatal diagnosis by fetal echocardiography (typically at 18–22 weeks gestation) allows delivery at a centre with paediatric cardiac surgery capability and planned prostaglandin E1 infusion at birth to maintain ductal patency while surgical planning is completed. Prostaglandin E1 infusion at 0.01–0.1 mcg/kg/min is started immediately after birth and continued until surgery. Families are counselled about the three-stage surgical pathway, the significant mortality risk of the Norwood (25–30% 30-day mortality at experienced centres), inter-stage mortality, neurodevelopmental risks, and the alternative of compassionate care or cardiac transplantation listing. The Norwood is not indicated for HLHS variants where biventricular repair is feasible after ventricular rehabilitation.

The neonate is brought to the operating room and placed on cardiopulmonary bypass (CPB) via ascending aortic and right atrial cannulation. Core temperature is progressively cooled to 18°C (deep hypothermia) and circulatory arrest initiated, giving the surgeon a bloodless field in which to perform the aortic reconstruction. The main pulmonary artery is transected and the branch pulmonary arteries are temporarily occluded. The small native ascending aorta is augmented and reconstructed into a 'neo-aorta' by anastomosing the pulmonary trunk to the ascending aorta, with patch augmentation of the aortic arch using homograft or Gore-Tex to correct any arch hypoplasia — this creates an unobstructed pathway from the right ventricle to the systemic circulation. The interatrial septum is excised (atrial septectomy) under direct vision to create unrestricted atrial communication. Controlled pulmonary blood flow is established with one of two techniques: the modified Blalock-Taussig (BT) shunt — a 3.5–4 mm polytetrafluoroethylene (PTFE) tube graft connecting the innominate artery to the right pulmonary artery — or the Sano shunt — a 5 mm PTFE conduit connecting the right ventricle directly to the branch pulmonary artery. The patient is rewarmed and weaned off CPB. The chest is often left open (open sternum) for 48–72 hours if oedema is anticipated, and closed on the third to fifth post-operative day.

Without the Norwood procedure, HLHS is uniformly fatal; thus the primary benefit is survival itself, converting a universally lethal condition into a survivable one with a reasonable long-term prognosis. The three-stage Norwood-Glenn-Fontan palliation achieves survival to Fontan completion in 50–70% of patients at high-volume centres, with those completing all three stages having a 10-year survival of 60–80% (Hypoplastic Left Heart Syndrome Registry, Pediatrics 2012). Surviving Fontan patients can attend mainstream school, participate in moderate physical activity, and achieve meaningful quality of life, with neurodevelopmental support optimising educational and social outcomes. The Norwood also provides parents and families with a planned medical pathway and avoids neonatal death within days of birth. Advances including modified ultrafiltration on CPB, antegrade cerebral perfusion during DHCA (replacing full circulatory arrest with selective brain perfusion at higher temperatures), improved PCICU monitoring protocols including near-infrared spectroscopy for cerebral oximetry, and the inter-stage home monitoring programme (weekly weight monitoring, pulse oximetry) have progressively improved Stage I survival at experienced centres from over 40% mortality in the early 1990s to 25–30% today at the best programmes, with some reporting 10–15% 30-day mortality.

The Norwood procedure carries the highest mortality of any congenital cardiac operation. Thirty-day mortality at experienced paediatric cardiac centres is 25–30%; at low-volume centres mortality may exceed 50%. Early post-operative complications include low cardiac output syndrome (the single right ventricle is pressure and volume overloaded supporting both circulations), shunt thrombosis causing acute desaturation and haemodynamic collapse (treated with emergency intervention — thrombolysis or surgical revision), pulmonary over-circulation if the shunt is too large (causing systemic hypoperfusion), and neurological injury from DHCA (periventricular leukomalacia, stroke, seizures) affecting up to 30% of neonates. Between the Norwood and Stage II Glenn, inter-stage sudden death occurs in 5–15% — most commonly from shunt thrombosis or acute haemodynamic decompensation — which is the rationale for the standardised home monitoring programme with daily weight and SpO2 recording. Long-term risks after Fontan completion include protein-losing enteropathy (3–5% per year), plastic bronchitis, Fontan-associated liver disease (fibrosis progressing to cirrhosis), arrhythmias, thromboembolic events, and Fontan failure requiring heart transplantation in 20–30% by mid-adulthood. Neurodevelopmental impairment — particularly deficits in executive function, attention, and processing speed — affects the majority of HLHS survivors and requires long-term specialist support.

After the Norwood procedure, neonates are admitted to the paediatric cardiac intensive care unit (PCICU) for 2–4 weeks of intensive haemodynamic monitoring and management. The early post-operative period is the most vulnerable: oxygen saturations of 75–85% are the physiological target (reflecting balanced pulmonary and systemic blood flow), rather than the normal range of 95–100%. The balance between pulmonary vascular resistance and systemic vascular resistance is manipulated pharmacologically with milrinone, dopamine, oxygen concentration adjustments, and occasionally inhaled carbon dioxide or nitric oxide to maintain this delicate equilibrium. Feeding via nasogastric tube is introduced cautiously and caloric intake optimised for the increased metabolic demands of the single ventricle heart. Discharge home occurs at 4–6 weeks if haemodynamically stable, with an organised inter-stage monitoring programme: parents are trained to record daily weight, oxygen saturation (home pulse oximeter), and feeding intake and to contact the cardiac team urgently if weight loss exceeds 30 g per day, oxygen saturation falls below the prescribed alarm threshold, or feeding deteriorates. Stage II — the bidirectional Glenn operation (superior vena cava to pulmonary artery anastomosis) — is performed at 4–6 months of age when pulmonary vascular resistance has fallen sufficiently. Stage III — the Fontan completion (inferior vena cava to pulmonary artery anastomosis) — is performed at 2–4 years. All HLHS patients require lifelong specialist cardiology follow-up.