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Hypoplastic Left Heart Syndrome Medical and Surgical Management

Michael E. Mitchell, MD , is medical director of Cardiothoracic Surgery at Children’s Hospital of Wisconsin and professor of Cardiothoracic Surgery at the Medical College of Wisconsin.

Hypoplastic left heart syndrome is one of the most severe congenital heart defects. It occurs in 0.016 to 0.036 percent of live births and makes up between 1.4 to 3.8 percent of congenital heart disease. It is associated with hypoplasia of the ascending and transverse aorta, stenosis or atresia of the aortic valve, stenosis or atresia of the mitral valve, and hypoplasia of the left ventricle.

It varies as to when a patient presents clinically with HLHS, depending on ductal patency and the degree of atrial level restriction. A quarter of infants present during the first 24 hours after birth. Most infants present after 48 hours with feeding difficulties and respiratory distress that can rapidly progress to congestive heart failure and shock. If unrecognized or untreated, this condition is uniformly fatal, accounting for 25 percent of infant cardiac deaths during the first week of life and 15 percent during the first month of life.

 Typical appearance of a hypoplastic arch
in hypoplastic left heart syndrome

Until the 1990s, the treatment of HLHS was associated with surgical mortality rates approaching or exceeding 90  percent.Children’s Hospital of Wisconsin has the best-reported outcomes in the treatment of HLHS, with the lowest-reported mortality rates (less than 6 percent)  for the critical first-stage Norwood procedure. We have achieved these results through teamwork and innovations in prenatal diagnosis, neonatal management, surgical innovation, postoperative monitoring, and home monitoring following discharge.

 Diagnosis and neonatal management 

The majority of HLHS cases in Wisconsin are diagnosed prenatally, allowing for planned delivery at a center of excellence and the immediate initiation of prostaglandins to maintain patency of the ductus arteriosus. Diagnosis is often made when a prenatal ultrasound indicates a hypoplastic left ventricle. Following delivery, postnatal echocardiography is essential to confirm the diagnosis and to make observations on several critical anatomic points, including the following:

  • Atrial septum: An intact or restrictive atrial septum results in obligate obstruction to pulmonary venous return, wet lungs, and moderate to severe hypoxia requiring emergent intervention with atrial septectomy.
  • Aorta: Severely hypoplastic aortas can be as tiny as 1 millimeter, essentially the size of a neonatal coronary artery, and result in reconstructive challenges at the time of the Norwood operation.
  • Tricuspid valve: The tricuspid valve will serve as the systemic AV valve and can be associated with insufficiency, requiring repair at the time of the Norwood operation.

Preoperative management

HLHS results in a parallel circulation with each cardiac contraction ejecting blood from the right ventricle to both the lungs and the systemic circulation via the patent ductus arteriosus. Following initial diagnosis and stabilization with prostaglandin E1, newborns with HLHS are managed with therapies directed at balancing systemic and pulmonary circulation, critically avoiding pulmonary overcirculation and systemic underperfusion as the pulmonary vascular resistance drops.

Children’s Hospital of Wisconsin has championed the consistent use of two-site NIRS monitoring of tissue oxygen saturation to ensure adequate tissue perfusion and to allow the real-time optimization of clinical measures to balance the circulations. If the ductus arteriosus is widely patent, prostaglandin E1 is initiated at 0.01 mcg/kg/minute. The most common side effect is apnea and is often managed with intravenous caffeine, minimizing the need for preoperative intubation. Pulse oximetry is typically in the low to mid-90s for the relatively asymptomatic neonate with HLHS. Initial palliation most commonly occurs during the first week of life.

Operative management

Surgical management of HLHS involves three operations. The first and most significant is the Norwood procedure, which entails an atrial septectomy, aortic arch reconstruction with combination of the pulmonary artery and the hypoplastic aorta as a single outflow tract, and creation of a source of pulmonary blood flow either via a right ventricle to pulmonary artery conduit (Sano shunt) or via a shunt from the innominate artery to the pulmonary artery (Blalock-Taussig shunt). Our center has pioneered several technical improvements on arch reconstruction and on the creation of right ventricle to pulmonary artery conduits.

Perioperative management

The patient with HLHS faces similar physiologic challenges prior to surgery, during the early postoperative period and through the interstage period until the second-stage palliation. The single right ventricle inefficiently pumps blood in parallel to the pulmonary and systemic vascular beds. Given the low pulmonary vascular resistance, systemic blood flow remains at risk regardless of optimal shunt size and placement. At the time of the second operation, the child is no longer shunt-dependent for pulmonary blood flow, and the heart pumps blood to the systemic vascular bed alone, leading to more efficient circulation.

Typical appearance of a hypoplastic aortic arch
in hypoplastic left heart syndrome

To attenuate the expected increases in systemic vascular resistance at the time of the Norwood operation, we routinely use pharmacologic alpha blockade. This tactic, along with perioperative monitoring of venous oximetry and multisite near-infrared spectroscopy of oxygen delivery to the brain and kidney region, was pioneered at Children’s Hospital of Wisconsin and has been widely adopted across the globe. These strategic improvements that target optimizing oxygen delivery have paralleled improved survival and been linked to improved neurologic outcomes.

Home monitoring between Norwood operation and Stage 2 palliation

The average hospital stay after the Norwood operation is five weeks. Due to the persistence of high-risk, vulnerable circulation at discharge, vigilant monitoring is necessary to identify destabilizing pathology and ensure adequate nutrition and somatic growth. Initiation of a home monitoring program between discharge after the Norwood operation and the second-stage operation marks another milestone in the management of HLHS that has increased survival rates. The home monitoring program pioneered at Children’s in 2000 reduced local interstage mortality from 15 percent to 1 percent, and more than 50 institutions nationwide have adopted our home monitoring program. 


To detect acute hypoxemia, dehydration and somatic growth deficiency, patients are discharged with an infant scale and pulse oximeter so parents can obtain daily saturations and weights. Pulse oximetry less than 75 percent or greater than 90 percent, weight loss of 30 grams or failure to gain 20 grams over two days prompts a call to a member of the dedicated home monitoring team for investigation. Additionally, patients are enrolled in a high-risk interstage clinic staffed by cardiology nurse practitioners, dietitians, speech pathologists, cardiologists and cardiac intensivists.


Beyond infancy

Care of children with HLHS is most intensive during the first few months of life. Stage 2 palliation is most commonly performed at 4 to 5 months of age and the third Fontan operation at 2 to 4 years of age. Completion of the Fontan operation does not mark the end of interventions, however, as these patients have a lifelong risk of arrhythmias that may require a pacemaker and heart failure refractory to medical management that can lead to cardiac transplantation. Furthermore, these patients are likely to have extracardiac morbidity, necessitating ongoing collaboration with numerous physician specialists, therapists, psychologists, social workers and others. For the first time in history, large cohorts of children with HLHS are developing into adolescents and young adults. Thus, it’s important to incorporate strategies to facilitate their development into routine clinical surveillance and care.


  1. Construction of the Right Ventricle-to-Pulmonary Artery Conduit in the Norwood: The “Dunk” Technique. James S. Tweddell, MD; Michael E. Mitchell, MD; Ronald K. Woods, MD; Thomas L. Spray, MD; and James A. Quintessenza, MD. Operative Techniques in Thoracic and Cardiovascular Surgery. 2012.
  2. Perioperative monitoring in high-risk infants after stage 1 palliation of univentricular congenital heart disease. Nancy S. Ghanayem, MD; George M. Hoffman, MD; Kathleen A. Mussatto, PhD, RN; Michelle A. Frommelt, MD; Joseph R. Cava, MD; Michael E. Mitchell, MD; and James S. Tweddell, MD. Journal of Thoracic and Cardiovascular Surgery. 2010 Oct;140(4):857-63.
  3. Perioperative cerebral oxygen saturation in neonates with hypoplastic left heart syndrome and childhood neurodevelopmental outcome. George M. Hoffman, MD; Cheryl L. Brosig, PhD; Kathleen A. Mussatto, PhD, RN; James S. Tweddell, MD; and Nancy S. Ghanayem, MD. Journal of Thoracic and Cardiovascular Surgery. 2013 Nov;146(5):1153-64.
  4. Monitoring the brain before, during, and after cardiac surgery to improve long-term neurodevelopmental outcomes. Nancy S. Ghanayem, MD; Michael E. Mitchell, MD; James S. Tweddell, MD; and George M. Hoffman, MD. Cardiology in the Young. 2006 Sep;16 Suppl 3:103-9.

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