Pediatric Hypoplastic Left Heart Syndrome Treatment & Management

Updated: Dec 15, 2020
  • Author: Syamasundar Rao Patnana, MD; Chief Editor: Stuart Berger, MD  more...
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Approach Considerations

No consensus has been reached in the approach to the treatment of neonates with hypoplastic left heart syndrome (HLHS). Supportive care, multistage surgical intervention (ie, Norwood, Glenn, and Fontan procedures) and cardiac transplantation are available options. A thorough explanation of each of these options, including their advantages and disadvantages, should be provided to the parents.

Occasionally, some anatomic features favor one choice over the others. In the presence of severe tricuspid or pulmonary valve anomalies, the multistage surgical approach is not likely to be beneficial; cardiac transplantation is the only surgical choice. In most cases, the choice of treatment is based on the parents' preference. While such a decision is being made, the infant should be stabilized.

If supportive care is chosen by the parents, they need strong emotional support because the condition is fatal without active treatment.


Medical Care

Prenatal diagnosis of hypoplastic left heart syndrome (HLHS) by fetal echocardiography is possible. When the HLHS is identified, it is advisable to have the baby deliver at an institution where tertiary care, including neonatal cardiac surgery, is performed routinely. There was some suggestion in the past that elective cesarean delivery may provide better outcomes. A recent study examining this issue found that there was no hemodynamic advantage for elective cesarean delivery section over vaginal delivery. [48]

Successful preoperative management depends on providing adequate systemic blood flow while limiting pulmonary overcirculation.

Note the following:

  • Initial preoperative management and postoperative care of hypoplastic left heart syndrome (HLHS) take place in the neonatal, pediatric, or cardiac ICUs.

  • When postoperative patients are clinically stable, transfer them to the general cardiac unit for adjusting oral medications, addressing feeding issues, and completing discharge teaching.

  • Involve a pediatric cardiologist during any noncardiac hospital admission of a patient who is status post (S/P) Norwood procedure. This is because of the complex cardiovascular physiology in infants after this surgery.

  • Hospitalization and inpatient care may be required for cardiac catheterizations, catheter interventions, and surgical procedures and for treatment of intercurrent infections as well as for management of postsurgical complications, including those after Fontan operation.

Open the ductus arteriosus

Blood flow to the systemic circulation (coronary arteries, brain, liver, kidneys) depends on flow through the ductus arteriosus. If a diagnosis of hypoplastic left heart syndrome is suspected, start prostaglandin E1 infusion immediately to establish ductal patency and ensure adequate systemic perfusion.

If the diagnosis is made prenatally or when the infant is relatively asymptomatic, a smaller dose of prostaglandin E1 may be sufficient to keep the ductus arteriosus patent while limiting its side effects.

A larger dose of prostaglandin E1 is often required to reopen the ductus arteriosus if an infant has cardiovascular collapse and shock due to ductal closure.

Ideally, prostaglandin E1 is administered centrally via an umbilical venous catheter.

Correct metabolic acidosis

Metabolic acidosis indicates inadequate cardiac output to meet the metabolic demands of the body. Acidosis adversely affects the myocardium.

Correction of metabolic acidosis with sodium bicarbonate infusion is essential in early management. This therapy is futile if the ductus arteriosus remains constricted.

Manipulate pulmonary vascular resistance

The pulmonary vascular resistance of a newborn is slightly less than the systemic vascular resistance and begins to fall soon after birth. In the patient with hypoplastic left heart syndrome, decreased pulmonary vascular resistance causes increased pulmonary blood flow and an undesirable obligatory decrease in systemic blood flow. Increased alveolar oxygen decreases pulmonary vascular resistance, leading to increased pulmonary blood flow. Therefore, oxygen should not be administered unless pulmonary parenchymal disease or pulmonary edema, causing severe hypoxemia, is present. The oxygen should be discontinued once these abnormalities resolve.

Consequently, most infants should remain in room air with acceptable oxygen saturation (pulse oximeter) in the low 70s. An exceptional circumstance is the infant with severe hypoxemia caused by pulmonary venous hypertension.

Achieving a slightly higher PaCO2, in the range of 45-50 mm Hg, can increase pulmonary vascular resistance. This can be accomplished by intubation, sedation, mechanical hypoventilation, or the addition of nitrogen or carbon dioxide (FIO2 of 15-19%) to the infant's inspired gas via the endotracheal tube or hood.

Intubation is not preferred. However, intubation and ventilation along with measures to balance pulmonary and systemic flows may improve tricuspid regurgitation. [49]

Serial blood gas analysis is necessary. Initially, an umbilical arterial catheter is useful to obtain frequent blood samples.

Although administration of subambient inspired oxygen to balance systemic and pulmonary blood flows is an attractive concept and should be applied during stabilization of the neonate, it should not be pursued for long periods because severe pulmonary hypertension may complicate the postoperative course. However, this does not seem to adversely affect the pulmonary vasculature on long-term follow-up. [50]



Inotropic support is indicated only in severely ill neonates with concurrent sepsis or profound cardiogenic shock and acidosis. The administration of inotropes can adversely affect the balance between pulmonary and systemic vascular resistance.

If needed, wean from inotropic support as soon as the infant is clinically stable.


Consider diuretics to manage pulmonary overcirculation before surgery. Agents commonly used include furosemide and spironolactone.


Antibiotics are indicated if the infant is at risk for antepartum infection.

Discontinue antibiotics after obtaining negative blood cultures.


Consult a pediatric cardiologist, pediatric cardiovascular surgeon, genetic specialist if a chromosomal abnormality is suspected, and an interventional pediatric cardiologist.


Transfer the infant to a hospital with appropriate ICUs. Pediatric cardiology and cardiovascular surgery services must be immediately available.

Carefully monitor the infant for apnea during transfer while on prostaglandin E1 therapy. If prostaglandin E1 has been started, consider elective endotracheal intubation before transfer.


Surgical Care

Sinha and associates, [15] Caylor and colleagues, [51] and Dotty and associates [52] proposed various palliative operations; however, survival was not feasible until Norwood and associates [3, 4] demonstrated that a multistage operative approach could be used to treat hypoplastic left heart syndrome.

After Fontan and Kreutzer's initial description of the physiologically corrective operation for tricuspid atresia, [53, 54] corrective surgery was widely adapted to treat this entity. The concept was extended to treat other cardiac defects with a functionally single ventricle, including hypoplastic left heart syndrome.

The originally described Fontan operation consisted of the following [53] :

  • Superior vena cava–to–right pulmonary artery end-to-end anastomosis (Glenn procedure)

  • Anastomosis of the proximal end of the divided right pulmonary artery to the right atrium directly or by means of an aortic homograft

  • Closure of the atrial septal defect

  • Insertion of a pulmonary valve homograft into the inferior vena caval orifice

  • Ligation of the main pulmonary artery, thus completely bypassing the right ventricle

Kreutzer performed anastomosis of the right atrial appendage and pulmonary artery directly or via a pulmonary homograft and closed the atrial septal defect. [54] A Glenn procedure was not performed, and a prosthetic valve was not inserted into the inferior vena cava. Fontan's concept was to use the right atrium as a pumping chamber [53] ; therefore, he inserted prosthetic valves into the inferior vena cava and right atrial–pulmonary artery junction. Kreutzer’s view was that the right atrium may not function as a pump and that the left ventricle functions as a suction pump in the system. [54]

Numerous modifications to the aforementioned procedures were undertaken by these and other workers in the field (see Tricuspid Atresia). Currently, staged total cavopulmonary connection is the procedure of choice. [55]

The goal of surgical reconstruction of hypoplastic left heart syndrome is to eventually separate the pulmonary and systemic circulations by achieving a Fontan circulation. The right ventricle remains the systemic ventricle while blood passively flows to the lungs. This ultimate reconstruction is accomplished in the following 3 stages:

Norwood procedure (stage I)

This procedure is usually performed during the first weeks of life, after the infant has been stabilized in the neonatal intensive care unit (ICU). The goals of the procedure are (1) to establish reliable systemic circulation without the ductus arteriosus and (2) to provide enough pulmonary blood flow for adequate oxygenation, while simultaneously protecting the pulmonary vascular bed in preparation for stages II and III.

The Norwood procedure includes (1) performing an atrial septectomy to provide unrestricted blood flow across the atrial septum, (2) ligating the ductus arteriosus, (3) creating an anastomosis between the main pulmonary artery and the aorta to provide systemic blood flow, (4) eliminating coarctation of the aorta, and (5) placing an aorta–to–pulmonary artery shunt (usually a modified Blalock-Taussig shunt) to provide pulmonary circulation.

Connecting a Gore-Tex graft from the right ventricular outflow tract to the pulmonary artery (ie, Sano operation) was advocated instead of conventional modified Blalock-Taussig (BT) shunt; [56, 57] some surgeons showed better results with the Sano procedure than with the conventional Norwood approach. [58] However, prospective randomized studies from a single institution, [59] as well as multiple institutions, [60] compared the techniques and have not found significant advantage of Sano over Blalock-Taussig shunt or vice versa.

Upon hospital discharge, most infants remain on digoxin to augment cardiac function, on diuretics to help manage right ventricular volume overload, and on aspirin to prevent thrombosis of the shunt. If tricuspid regurgitation is present, use afterload reduction with captopril. [3] Oxygen saturation is typically 70-80% in room air. [5]

A retrospective study (2005-2013) reported that mitral stenosis and aortic atresia was a risk factor for perioperative myocardial ischemia and mortality in patients who underwent a modified Norwood procedure. [61] Compared to patients with other hypoplastic left heart syndrome anatomic subgroups, operative mortality was higher in the mitral stenosis/aortic atresia group (29% vs 7%) and accounted for 50% of the total operative mortality, despite the mitral stenosis/aortic atresia patients comprising only 19% of the total study population. [61]

Bidirectional Glenn procedure (stage II)

This procedure is performed approximately 6 months after the Norwood procedure. Before surgery, perform a cardiac catheterization to assess right ventricular function, pulmonary artery anatomy, and pulmonary vascular resistance. If results are favorable, schedule elective surgery.

The bidirectional Glenn procedure includes creating an anastomosis between the superior vena cava and the right pulmonary artery, end-to-side so that venous return from the upper body can flow directly into both lungs. In the hemi-Fontan, the superior vena cava–right atrial junction is closed with a patch that is removed during the next stage. Blood from the inferior vena cava continues to drain into the right atrium. The aorta–to–pulmonary artery shunt that was placed at stage I is ligated.

When both right and left superior vena cavae are present, bilateral bidirectional Glenn shunts should be performed, especially if the bridging innominate vein is absent or small.

At the time of bidirectional Glenn, repair of pulmonary artery narrowing, if present, should be undertaken. Issues related to tricuspid valve regurgitation, restrictive atrial septum and any other abnormalities should also be addressed.

At discharge, infants usually remain on digoxin, diuretics, aspirin, and captopril for the reasons mentioned above.

Fontan procedure (stage III)

The Fontan procedure is performed approximately 12 months after the bidirectional Glenn procedure. Again, catheterization is necessary to ensure that the child is a candidate for surgery.

Completion of the Fontan procedure includes directing blood flow from the inferior vena cava to the pulmonary arteries either via a lateral tunnel procedure or via an extracardiac conduit. Extracardiac conduit diversion of inferior vena caval blood into the right pulmonary artery is currently preferred by most surgeons. To address the growth issue related to extracardiac Fontan, some surgeons use autologous pericardial roll grafts. At the conclusion of the procedure, systemic venous blood returns to the lungs passively without passing through a ventricle.

Choussat et al's criteria have been modified by many cardiologists and surgeons. [62] Patients violating these criteria are at a higher risk for poor prognosis following Fontan operation than patients within the limits set by Choussat. In this high-risk group, the concept of leaving a small atrial septal defect open to facilitate decompression of the right atrium has been advanced. Laks et al advocated closure of the atrial defect by constricting the preplaced suture in the postoperative period, [63] whereas Bridges et al used a transcatheter closure technique. [64] Although the fenestrated Fontan was initially conceived for high-risk patients, it has since been used in patients with modest or even low risk. Rare reports of cerebrovascular or other systemic arterial embolic events following the fenestrated Fontan procedure tend to contraindicate its use in non–high-risk patients. Some studies suggest routine fenestration is unnecessary [65]

At discharge, most children remain on digoxin, diuretics, aspirin, and captopril if necessary. In an uncomplicated case, most of these medications can be weaned over 6 months following the Fontan operation. Some cardiologists advocate using aspirin indefinitely. Routine use of more aggressive anticoagulation with Coumadin is debated. When warfarin and aspirin regimens were compared, no difference in thrombotic complications between the groups was detected. [66] Similar early uncontrolled studies indicated similar finding; thus, most pediatric cardiologists use aspirin for prevention of thrombotic events in children. Use of more potent drugs such clopidogrel (Plavix) may be reasonable in adolescents and adults.

Ruotsalainen et al investigated the impact of initial shunt type, comparing outcomes of a Blalock-Taussig (BT) shunt with a right ventricle to pulmonary artery conduit (RV-PA), on myocardial function at different stages of surgical palliation in a population-based cohort of 63 Finnish children with hypoplastic left heart syndrome. Investigators studied patients retrospectively by echocardiography prior to stages I, II, and III palliation and 0.5-3 years after stage III. Patients with a BT shunt had better systolic performance after stage III compared to patients with an RV-PA conduit. [67]

Heart transplantation is another surgical option. [5, 6] The infant must remain on prostaglandin E1 infusion to keep the ductus arteriosus patent while waiting for a donor heart to become available. Approximately 20% of infants listed for heart transplantation die while waiting for a suitable donor organ. After successful cardiac transplantation, infants require multiple medications for modulation of the immune system and prevention of graft rejection. Perform frequent outpatient surveillance to identify rejection early and prevent lasting damage to the transplanted heart. Periodic endomyocardial biopsy usually is performed for more precise monitoring.

Emerging therapies

Catheter-assisted Fontan

Following Norwood procedure, 2-stage cavopulmonary connection is currently recommended for achieving Fontan circulation. Konert et al proposed a staged surgical-catheter approach; [68] they initially perform a modified hemi-Fontan procedure that is later completed by transcatheter methodology. This reduces the total number of operations required.

The modified hemi-Fontan procedure involves the usual bidirectional Glenn procedure. The lower end of the divided superior vena cava is anastomosed to the undersurface of the right pulmonary artery. The superior vena cava is then banded around a 16-gauge catheter with 6-0 Prolene slightly above the cavoatrial junction. A lateral tunnel with a Gore-Tex baffle is created, diverting the inferior vena caval blood toward the superior vena cava. The Gore-Tex baffle is then fenestrated with three to five 5-mm holes. Thus, the first stage achieves a physiologic bidirectional Glenn procedure.

At the time of the second stage (the transcatheter stage), the superior vena caval constriction is balloon dilated, and fenestrations are closed with devices or by placement of covered stent. These procedures have been performed in a limited number of patients, and preliminary data suggest that the usual post-Fontan operation complications, such as pleural effusion and ascites, have not occurred with this approach. Additional experience is reported; [69, 70] however, scrutiny of results of larger experience and longer-term follow-up and ready availability of covered stents are necessary for routine application of this innovative approach. To the authors knowledge, this approach is not well documented in patients with hypoplastic left heart syndrome.

Sano’s modification of the Norwood procedure

Because of high mortality that Sano and his associates observed with the conventional Norwood procedure, they performed right ventricular outflow–to–pulmonary artery Gore-Tex graft anastomosis to provide for the pulmonary blood flow instead of conventional modified aortopulmonary shunt. [56, 57] Significant improvement was demonstrated in both immediate and late mortality with this modification. [58]

A multi-institutional study comparing the results of these 2 types of stage I palliation of hypoplastic left heart syndrome suggested no significant difference between the groups. [60]

Other hybrid approaches

Again, because of high mortality following stage I Norwood reconstruction, several groups have performed bilateral banding of the branch pulmonary arteries via median sternotomy and implant stent in the ductus arteriosus. [71, 72] Maintaining ductal patency with long-term prostaglandin infusion instead of ductal stenting is advocated by some. At the time of the second stage, aortic arch reconstruction, atrial septectomy, and bidirectional Glenn shunt are performed. This is followed by Fontan conversion. Although reduction of early mortality is theoretically feasible, larger experience with this approach than is currently available is necessary prior to general adaptation of this method of management of hypoplastic left heart syndrome.

Bugnitz et al evaluated right ventricular functional changes in 20 neonates with hypoplastic left heart syndrome who underwent the hybrid procedure under steady-state conditions. Systolic and diastolic functions significantly decreased after the hybrid procedure, even though patients avoided cardiopulmonary bypass. Results were comparable with prior reports in patients with hypoplastic left heart syndrome who underwent the Norwood procedure. [73]

Prevention by fetal intervention

Fetal echocardiography studies have shown development of hypoplastic left heart syndrome in fetuses initially found to have severe/critical aortic stenosis or absent of markedly restrictive patent foramen ovale. Some data suggest that fetal intervention to relieve aortic valve stenosis (by balloon aortic valvuloplasty) or creation of atrial septal defects (by percutaneous septostomy), both under the guidance of ultrasonography), may promote normal development of the left ventricle or confer benefit following birth. [74, 75] Further research into this type of approach is needed.



Adequate nutrition is important before and after surgery. Many infants require nasogastric feeding with increased-calorie breast milk or formula after the Norwood procedure. [76] Routine insertion of gastrostomy tube in the immediate postoperative period is used in some institutions to provide adequate caloric intake. However, normal oral feeding is reestablished with time. Adequate oral iron intake prevents development of iron deficiency anemia.

After completion of the Fontan operation, specific dietary restrictions are not necessary unless protein-losing enteropathy develops. [45] In such cases, a medium-chain triglyceride diet may be helpful.



Specific activity restrictions are not imposed on children after completion of the Fontan operation. In general, encourage children to participate in activities that they are able to tolerate. Children who underwent a Fontan procedure may not be able to tolerate highly competitive sports.

Studies have shown that these children may have impaired exercise performance when compared to age-matched peers. Perform an exercise stress test when the child is old enough.

Neurodevelopmental abnormalities occur often in patients with hypoplastic left heart syndrome.


Long-Term Monitoring

Note the following:

  • Schedule outpatient follow-up care 2 weeks after discharge in the typical postoperative patient.

  • Schedule those who are S/P cardiac transplantation earlier for necessary laboratory studies.

  • Earlier follow-up care is also necessary if a pericardial effusion is discovered on the discharge echocardiogram.

  • Periodic follow-up visits after stage I, II, and III operations are mandatory. Individualize outpatient follow-up care based on the needs of each patient.

  • Substantial (5-15%) interstage mortality (between stages I and II) is observed. [77] Restrictive atrial communication, obstruction of aortic arch (coarctation), obstructed Blalock-Taussig shunt or Sano shunt, pulmonary artery distortion, and tricuspid valve insufficiency are associated with interstage mortality. In addition, childhood GI or respiratory diseases may produce hypovolemia and/or acute hypoxemia, leading to interstage death. [77] Careful observation, follow-up and home surveillance with optimal nutrition with good growth may decrease interstage mortality. [78, 79] Interstage mortality between stage II (bidirectional Glenn) and stage III (Fontan) is lower that after stage I (Norwood) [80] ; however, follow-up is necessary.