Paeds · cardiology
Hypoplastic left heart syndrome
Also known as Hypoplastic left heart syndrome · HLHS · Single-ventricle physiology of the left heart · Aortic and mitral atresia · Norwood sequence · Univentricular heart of the left-heart type
Fellowship guide to hypoplastic left heart syndrome: the most severe ductal-dependent systemic-outflow obstruction, presenting as the day-two-to-four neonatal collapse with weak pulses and acidosis; the prostaglandin-E1-first resuscitation before the echo; the echocardiographic anatomy of atretic mitral and aortic valves with a hypoplastic ascending aorta and a right ventricle doing all the work; and the three-stage single-ventricle palliation — Norwood, Glenn, Fontan — whose SVR-trial evidence, interstage mortality and neurodevelopmental burden every candidate must own.
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- A neonate who was feeding and thriving then collapses on day two to four with weak pulses, mottled skin and metabolic acidosis has a ductal-dependent lesion until proven otherwise — start prostaglandin E1 immediately and do not wait for the echocardiogram, because the partially-open duct may still be reopenable
- A restrictive atrial septum in HLHS is a preoperative emergency: pulmonary venous return is trapped behind the left atrium, causing profound hypoxaemia and pulmonary oedema, and demands an urgent balloon atrial septostomy or atrial stent, not more oxygen
- The interstage period between the Norwood and the Glenn carries the highest mortality in the whole pathway — any fever, tachypnoea, poor feeding or colour change in an interstage infant is presumed circulatory failure until proven otherwise and is referred immediately
- Prostaglandin E1 apnoea is common and often requires intubation — an HLHS infant on PGE1 being retrieved must travel intubated or with airway expertise, because an unplanned apnoea in transit is a preventable death
- All pulses are weak in HLHS collapse, not just the femorals — this distinguishes it from coarctation where the upper-limb pulses remain strong, and the difference drives the bedside differential of ductal-dependent lesions
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- Hypoplastic left heart syndrome
- Ductal-dependent congenital heart disease
- Single-ventricle palliation: Norwood, Glenn and Fontan
- Neonatal collapse at ductal closure
- Neonatal cyanosis and collapse
- Prostaglandin E1 in ductal-dependent lesions
- Short case: post-Norwood infant in interstage
- Long case: Fontan survivor and late complications
- Single-ventricle circulations
- Staged palliation and the SVR trial
- Cardiovascular examination of the shocked neonate
- Ductal-dependent systemic circulation
- Patient Care: complex congenital heart disease
- Medical Expert: hypoplastic left heart syndrome
The single idea that organises this topic is that the right ventricle does all the work, and the ductus arteriosus is the lifeline: while the duct is open the baby survives, and when it closes the baby dies unless prostaglandin E1 reopens it. Every clinical feature, every resuscitation step and every surgical stage flows from that mechanism. [2] [3]
This page covers the recognition and neonatal stabilisation of HLHS, the echocardiographic anatomy, the three-stage palliation and the SVR-trial evidence behind the shunt choice, the interstage mortality that is the dominant modifiable risk, the neurodevelopmental burden, and the lifelong follow-up every Fontan survivor needs. It links to the ductal-dependent congenital heart disease leaf for the broader differential and to the neonatal cyanosis leaf for the saturation-based approach. [1] [2]
Overview & Definition
HLHS is not a single defect but a spectrum of underdevelopment of the left heart. The mitral and aortic valves are atretic or critically stenotic, the left ventricle is a slit-like or absent cavity that cannot generate systemic pressure, and the ascending aorta and arch are hypoplastic — sometimes thread-like — because they never carried meaningful forward flow in fetal life. The right ventricle is structurally normal and becomes the systemic ventricle, pumping the whole circulation. [2]
What makes HLHS lethal without intervention is its absolute ductal dependence. The right ventricle ejects into the pulmonary artery, and in HLHS the only route for that blood to reach the body is retrograde through the ductus arteriosus into the descending aorta, and from there back up the hypoplastic arch to the head, neck and coronary arteries. While the duct is patent in fetal life and the early hours after birth, this parallel circulation sustains the child. The moment the duct constricts, systemic output collapses. [3]
HLHS sits at the severe end of the ductal-dependent congenital heart disease family, alongside coarctation, interrupted aortic arch and critical aortic stenosis. The unifying principle for the general paediatrician is that any neonate who collapses after a period of wellbeing, with shock, acidosis and weak pulses, has a ductal-dependent lesion until proven otherwise and gets prostaglandin E1 before the echo. [2]
References12ShowHide
- [1]Ohye RG; Sleeper LA; Mahony L; et al Comparison of shunt types in the Norwood procedure for single-ventricle lesions. N Engl J Med, 2010.PMID 20505177
- [2]Feinstein JA; Benson DW; Dubin AM; et al Hypoplastic left heart syndrome: current considerations and expectations. J Am Coll Cardiol, 2012.PMID 22192720
- [3]Rychik J Hypoplastic left heart syndrome: can we change the rules of the game? Circulation, 2014.PMID 25052402
- [4]Ghanayem NS; Allen KR; Tabbutt S; et al Interstage mortality after the Norwood procedure: Results of the multicenter Single Ventricle Reconstruction trial. J Thorac Cardiovasc Surg, 2012.PMID 22795436
- [5]Ahmed H; Anderson JB; Krawczeski PA; et al Development of a validated risk score for interstage death or transplant after stage I palliation for single-ventricle anatomy. J Thorac Cardiovasc Surg, 2020.PMID 31924360
- [6]Rudd NA; Ghanayem NS; Hill GD; et al Interstage Home Monitoring for Infants With Single Ventricle Heart Disease: Education and Management. J Am Heart Assoc, 2020.PMID 32777961
- [7]Ahmed H; Oster ME; Krawczeski PA; et al Characteristics of Interstage Death After Discharge from Stage I Palliation. Pediatr Cardiol, 2021.PMID 33948710
- [8]Newburger JW; Sleeper LA; Gaynor JW; et al Transplant-Free Survival and Interventions at 6 Years in the SVR Trial. Circulation, 2018.PMID 29437119
- [9]Goldberg CS; Trachtenberg FL; Krawczeski PA; et al Longitudinal Follow-Up of Children With HLHS and Association Between Norwood Shunt Type and Outcomes. Circulation, 2023.PMID 37795623
- [10]Sananes R; Goldberg CS; Bove EL; et al Six-Year Neurodevelopmental Outcomes for Children With Single-Ventricle Physiology. Pediatrics, 2021.PMID 33441486
- [11]Bergemann A; Hansen JH; Rotermann I; et al Neuropsychological performance of school-aged children after staged surgical palliation of hypoplastic left heart syndrome. Eur J Cardiothorac Surg, 2015.PMID 25100716
- [12]Oster ME; Chen S; Kugler JD; et al Development and impact of arrhythmias after the Norwood procedure: A report from the Pediatric Heart Network. J Thorac Cardiovasc Surg, 2017.PMID 27939495