eMedicine Specialties > Pediatrics: Cardiac Disease and Critical Care Medicine > Cardiothoracic Surgery

Hypoplastic Left Heart Syndrome and the Staged Norwood Procedure

Richard G Ohye, MD, Director, Pediatric Cardiac Transplantation, Fellowship Program Director, Pediatric Cardiac Surgery, Assistant Professor, Department of Surgery, Section of Cardiac Surgery, University of Michigan Medical Center
Ralph S Mosca, MD, Director, Pediatric Cardiac Surgery, Associate Professor, Department of Surgery, New York Presbyterian Medical Center; Edward L Bove, MD, Associate Director, PICU, CS Mott Children's Hospital; Director, Department of Surgery, Section of Thoracic Surgery, Division of Pediatric Cardiovascular Surgery, Professor, University of Michigan Medical Center

Updated: Jul 15, 2008

Introduction

Hypoplastic left heart syndrome (HLHS) refers to a constellation of congenital cardiac anomalies characterized by marked hypoplasia or absence of the left ventricle and severe hypoplasia of the ascending aorta.

The first successful palliation of HLHS was reported by Norwood et al in a series of infants who underwent surgery from 1979-1981.¹ The procedure has been technically refined over the years, but the essential components remain (1) atrial septectomy, (2) anastomosis of the proximal pulmonary artery to the aorta with homograft augmentation of the aortic arch, and (3) aortopulmonary shunt (or right ventricle–to–pulmonary artery conduit [RVPAC]). Staged orthoterminal correction of HLHS with a Fontan operation using the right ventricle as the systemic ventricle was first reported in 1983 by Norwood et al.² More recent reviews describe continued improvement in short-term and long-term survival rates.

An alternative approach to staged reconstructive surgery is orthotopic cardiac transplantation. This was first successfully performed by Bailey in November 1985 when he transplanted the heart and ascending aorta of an 8-day-old neonate into a 4-day-old 2.8-kg infant.³ This followed years of research, including experimentation with xenotransplantation.⁴ The advantage of cardiac transplantation is replacement of an abnormal circulation with a normal 4-chambered heart in a single operation. Chief disadvantages of this approach are the limited availability of donor hearts and the requirement for lifelong immunosuppression.

Dramatic improvements in both staged reconstructive approaches and transplantation techniques have been achieved in recent years. Currently, both staged reconstruction and transplantation have a role in the management of HLHS. Staged reconstruction includes 3 procedures with an overall 5-year survival rate of approximately 70%. Long-term durability of the tricuspid valve and right ventricle at systemic workloads remains to be determined.

Cardiac transplantation offers a single operation with, perhaps, a lower operative mortality rate; however, 25% of neonates listed for transplantation do not receive donor hearts. In addition, after transplantation, neonates face a lifetime of immunosuppression with the attendant risks of rejection and infection. Both staged reconstructive surgery and transplantation have shown remarkable improvements in results with ongoing evolution of surgical techniques and improvements in perioperative care.

Supportive care only, without intervention, is becoming a less acceptable alternative for neonates with HLHS. Recommendations by any given pediatric cardiac surgical unit must take into consideration that center's results and expertise with the 2 approaches. Surgical techniques and results of staged reconstruction are reviewed in this article (see Surgical therapy).

History of the Procedure

The term hypoplastic left heart syndrome was introduced by Noonan and Nadas in 1958 to describe the morphologic features of combined aortic atresia and mitral atresia.⁵ This followed Lev's description in 1952 of congenital cardiac malformations associated with underdevelopment of the chambers on the left side and a small ascending aorta and arch.⁶

Frequency

HLHS is a relatively common form of congenital heart disease, occurring in 7-9% of neonates in whom heart disease is diagnosed in the first year of life. Without surgical intervention, HLHS is fatal, accounting for 25% of cardiac deaths in the first week of life.

Etiology

Although the etiology of HLHS is unknown, Lev has postulated that premature narrowing of the foramen ovale leads to a faulty transfer of blood from the inferior vena cava (IVC) to the left atrium during fetal life.⁷ Thus, altered intrauterine hemodynamics may be the physiologic cause of HLHS. Other authors have postulated that the embryologic cause is severe underdevelopment of the left ventricular outflow in the form of isolated aortic valve atresia. This aortic atresia results in abnormal development of the remaining cardiac structures, resulting from the associated blood flow patterns.

Pathophysiology

Systemic circulation depends on the right ventricle via a patent ductus arteriosus, and obligatory mixing of pulmonary and systemic venous blood occurs in the right atrium.

Presentation

HLHS is often diagnosed in patients during the newborn period because of tachypnea and cyanosis within 24-48 hours of birth. When the ductus arteriosus begins to close, diminished systemic perfusion rapidly occurs, with pallor, lethargy, and diminished pulses. Cardiac examination reveals a dominant right ventricular impulse, a single second heart sound, and a nonspecific soft systolic murmur at the left sternal border. Ductal closure results in diminished systemic perfusion with the development of metabolic acidosis and renal failure.

Indications

The presence of hypoplastic left heart syndrome (HLHS) is an indication for therapy. Without intervention, HLHS is essentially universally fatal within the first month of life. As survival rates for both staged repair and transplantation have improved, the continued role of comfort-measures-only therapy can be questioned. Certainly, both pediatric and adult patients routinely undergo therapy for conditions with far worse prognosis than HLHS.

Relevant Anatomy

Hypoplastic left heart syndrome (HLHS) refers to a constellation of congenital cardiac anomalies characterized by marked hypoplasia or absence of the left ventricle and severe hypoplasia of the ascending aorta.

Pathologic findings by Bharati et al in a series of 230 patients with HLHS included 105 with aortic atresia and mitral stenosis (45%), 95 with aortic and mitral atresia (41%), and 30 with severe aortic and mitral stenosis (13%).⁸ The dilated and hypertrophied right ventricle is the dominant ventricle and forms the apex of the heart. The tricuspid valve annulus is invariably dilated, and significant anomalies in morphology have been described in 5-7% of patients. Clinically significant tricuspid regurgitation has been reported by both Barber and Chang in 8-10% of patients studied and has been identified as a significant risk factor in short-term and long-term survival.^9,10

In 95% of these infants, the ventricular septum is intact and the left ventricular cavity is only a small slit with thick endocardial fibroelastosis. The ascending aorta is usually very small, ranging in size from 1-8 mm as measured using 2-dimensional echocardiography; mean diameter is 3.8 mm, and, in 55% of patients, the ascending aorta is smaller than 3 mm. The portion of ascending aorta between the atretic valve and the innominate artery serves only as a conduit for the retrograde flow of blood into the coronary arteries. The main pulmonary artery is very large and is the origin of a large ductus arteriosus that carries blood from the right ventricle into the aorta. A localized coarctation of the aorta is present in 80% of patients.

Contraindications

Other than the presence of a lethal chromosomal anomaly, other anomalies, or an extremely poor clinical condition, no absolute contraindications to surgical repair are recognized. However, several factors have been noted to convey higher surgical risk. Patients older than 1 month undergoing the Norwood procedure, patients with severe obstruction to pulmonary venous return, patients with significant noncardiac congenital conditions (eg, prematurity, low birth weight, chromosomal anomalies), and patients with the anatomic subtype of hypoplastic left heart syndrome (HLHS) with aortic atresia are at increased risk. Details of the outcomes for patients who are at standard-risk and those who are at high-risk are outlined in Outcome and Prognosis.

Workup

Laboratory Studies

• Routine laboratory studies, such as CBC count, platelets, electrolytes, BUN levels, creatinine levels, liver function tests, and coagulation studies, are indicated. In addition to ensuring that laboratory test values return to reference ranges, maintain the hematocrit level at 45% or more if the patient is cyanotic.
• Routine serial monitoring of ABGs is important in balancing the relative pulmonary and systemic blood flows in patients with single ventricle physiology (see Medical therapy, Surgical therapy).

Imaging Studies

• Chest radiography
  • Chest radiographs reveal cardiomegaly and increased pulmonary vascular markings.
  • In 2% of patients, a reticular pattern of obstructed pulmonary venous return is seen because of a restrictive atrial septal defect.
• Doppler echocardiography
  • Diagnosis is made using 2-dimensional and color Doppler echocardiography for determination of cardiac morphology and evaluation of the arch hypoplasia.
  • Color-flow Doppler images reveal that the blood flow in the ascending aorta is typically retrograde.

Other Tests

• Electrocardiography reveals right atrial enlargement and right ventricular hypertrophy.

Diagnostic Procedures

• Cardiac catheterization is rarely necessary. An exception would be to gain additional information in patients with borderline left ventricle size to assist in the decision-making process regarding the optimal treatment method.

Treatment

Medical Therapy

Oxygen saturation is monitored by pulse oximetry. Acidosis is rapidly reversed using sodium bicarbonate. The fraction of inspired oxygen (FIO₂) is adjusted to maintain a relative hypoxemia (oxygen saturation 75-80%), which aids in preventing the pulmonary vasodilatation associated with high oxygen concentrations. Even in the neonate who is being resuscitated because of circulatory collapse, ventilation with a high concentration of oxygen is avoided because it may only further decrease pulmonary vascular resistance and systemic blood flow.

Blood transfusion should be performed to maintain the hematocrit between 45-50%. Mechanical ventilation is avoided when possible, but infants on ventilation may require sedation with intravenous fentanyl to prevent tachypnea. In patients with significant pulmonary overcirculation, hypoventilation to maintain a mild respiratory acidosis (partial pressure of carbon dioxide [PCO₂] of 45-55 mm Hg) and elevation of pulmonary vascular resistance may be used. Occasionally, inhaled nitrogen or carbon dioxide can be added to reduce the FIO₂ to between 16-18% to increase pulmonary vascular resistance. Inotropic support is advantageous in patients with depressed right ventricular function.

Nourishment is usually provided via intravenous hyperalimentation, which avoids the added risk of necrotizing enterocolitis prior to surgery. Diuretics are added, as necessary, when pulmonary congestion becomes apparent. This regimen simulates the fetal balance of pulmonary and systemic vascular resistance, stabilizing the infant while deciding on therapeutic options.

Surgical Therapy

The goal of staged reconstruction is a Fontan procedure, creating separate pulmonary and systemic circulations supported by a single (right) ventricle. The initial stage must provide unobstructed systemic blood flow from the right ventricle to the aorta and coronary arteries, relieve any obstruction to pulmonary venous return, and limit pulmonary blood flow by virtue of an appropriately sized systemic–to–pulmonary artery shunt or RVPAC.

As a result of the relatively high pulmonary vascular resistance present in the newborn period, a systemic shunt is necessary, and the right ventricle performs the increased volume of work of both the pulmonary and systemic circulations. Preservation of right ventricular function has been aided by using smaller initial aortopulmonary shunts to limit right ventricular volume overload, by using an RVPAC, and by using an interim procedure between the Norwood and Fontan operations. This staging procedure, either a bidirectional Glenn anastomosis or a hemi-Fontan procedure, is usually performed at age 6 months.

Recently, the use of an RVPAC as an alternative to the traditional modified Blalock-Taussig shunt (MBTS) has been proposed. Initially described by Norwood in his original description of the Norwood procedure, the use of the MBTS quickly became the preferred source of pulmonary blood flow. In 2002, Sano and colleagues described their experience with the Norwood procedure, with improvements in hospital survival from 53-89% when compared with historical controls.¹¹ Several other groups also reported similar improvements in outcomes, based on historical controls. A recent comparison using nonrandomized, but contemporary, controls by Tabbutt and colleagues revealed no difference in hospital survival.¹²

The general trend in the literature has been that centers that have had difficulties in achieving optimal survivals with the Norwood procedure have found a benefit to using the RVPAC, whereas institutions that have had better success with the Norwood procedure have found no improvement. The optimal source of pulmonary blood flow remains to be determined. Each source has inherent advantages and disadvantages, and the long-term, or even intermediate-term, effects are unknown. The MBTS results in significant diastolic run-off and potential coronary steal. The RVPAC avoids this run-off but adds the undesirable need to place an incision on the right ventricle.

Currently, a multi-institutional, randomized, controlled trial is being performed by the Pediatric Heart Network with funding from the National Heart, Lung, Blood Institute of the National Institutes of Health. The trial is predicted to complete enrollment in June 2008. Allowing 12 months for the primary outcome of death or cardiac transplantation at 12 months, the results are anticipated to be published in late 2009.

Whichever source of pulmonary blood flow is selected, these procedures provide adequate pulmonary blood flow while decreasing volume overload to the right ventricle and improving effective pulmonary blood flow until the patient can undergo a completion Fontan procedure. As described in detail in Second-stage palliation: Hemi-Fontan or bidirectional Glenn anastomosis, the hemi-Fontan procedure is a modification of the bidirectional Glenn procedure. The hemi-Fontan procedure involves (1) a side-to-side connection between the superior vena cava (SVC)/right atrial junction and the pulmonary arteries, (2) routine augmentation of the branch pulmonary arteries, and (3) temporary patch closure between the pulmonary arteries and the right atrium.

Preoperative Details

See Medical therapy.

Intraoperative Details

First-stage palliation: Norwood procedure

Through a midline sternotomy, cardiopulmonary bypass (CPB) is established. A minimum of 20 minutes of cooling to a core temperature of 18°C is begun for deep hypothermic circulatory arrest. Alternatively, some groups have reported the use of regional low-flow cerebral perfusion in lieu of deep hypothermic circulatory arrest (see Future and Controversies).

Regardless of the technique used, the septum primum is completely excised (atrial septectomy). The ductus is ligated and divided. The main pulmonary trunk is proximally divided to the bifurcation of the pulmonary arteries. The resultant opening in the pulmonary artery is closed with a patch of pericardium, polytetrafluoroethylene, or homograft. The remaining ductal tissue (on the undersurface of the aortic arch) is completely excised, and the incision is extended at least 10 mm further down the descending aorta into a normal-appearing and normal-caliber aorta (see Media file 1). This incision is proximally extended under the transverse arch and down the diminutive ascending aorta until the level of the previously divided main pulmonary trunk is reached (see Media file 2).

A cryopreserved pulmonary allograft is trimmed to fashion a patch that serves to enlarge the aorta and allow anastomosis to the proximal main pulmonary trunk (see inset in Media file 2). The remainder of the aorta is attached to the pulmonary allograft, proximally incorporating the main pulmonary trunk. The cannulae are replaced to begin bypass and commence systemic rewarming to 37°C.

A polytetrafluoroethylene shunt is placed from the innominate artery to the central pulmonary artery during rewarming (see Media file 3). A 4-mm shunt is used in patients who weigh more than 3.5-4 kg; smaller patients receive a 3.5-mm shunt. The distal end of the shunt is centrally placed on the pulmonary arteries, rather than onto the right pulmonary artery, to promote even distribution of blood flow to both lungs. Alternatively, the right ventricle–to–pulmonary artery conduit can be placed. These polytetrafluoroethylene grafts are generally either 5 mm or 6 mm in diameter. 

The hemi-Fontan operation or a bidirectional Glenn anastomosis is typically performed in infants aged 3-10 months to minimize the period of time during which the right ventricle is subject to volume overload. Cardiac catheterization is performed prior to this procedure to evaluate pulmonary vascular resistance, pulmonary artery anatomy, tricuspid valve regurgitation, and right ventricular function.

To perform a bidirectional Glenn procedure, CPB is achieved with neoaortic arch cannulation and separate right-angle IVC and right-angle SVC cannulae. The aortopulmonary shunt is ligated and divided when CPB is initiated. If any stenosis of the pulmonary artery secondary to the prior shunt or patch is present, the stenosis is repaired with patch augmentation. The azygous vein is ligated and divided. The SVC is transected and anastomosed in an end-to-side fashion to the superior aspect of the right pulmonary artery. The cardiac end of the transected SVC is oversewn. Some groups routinely perform the bidirectional Glenn procedure without CPB, with or without an SVC-to–right aorta temporary shunt, during the anastomosis to minimize high cerebrovenous pressures.

The hemi-Fontan procedure has the same physiologic factors as a bidirectional Glenn anastomosis but includes an anastomosis of the pulmonary arteries to an incision in the atriocaval junction. The cavopulmonary connection may be performed under a brief period of deep hypothermic circulatory arrest. Alternatively, cannulation of the IVC and high on the SVC can be used to perform the procedure entirely during CPB.

Whether the procedure is performed under circulatory arrest or during CPB, the remainder of the procedure is the same. The aortopulmonary shunt is divided, and the pulmonary arteries are mobilized from the right to the left upper lobe. The azygous vein is ligated. The right atrium is opened along the superior aspect of the appendage, and a corresponding incision is made transversely along the confluence of the branch pulmonary arteries (see upper left of Media file 4). The posterior aspect of the right arteriotomy is anastomosed to the inferior aspect of the pulmonary arteriotomy (see upper right of Media file 4).

A patch of pulmonary allograft tissue is fashioned to augment the pulmonary arteries. The allograft patch is begun at the left upper lobe, incorporating a separate end-to-side anastomosis for a left SVC, if necessary (see lower portion of Media file 4). A patch is placed within the right atrium, which isolates SVC return into the pulmonary arteries and provides an unobstructed pathway for connection of IVC return during the Fontan procedure (see lower portion of Media file 4). The atrial septal defect is inspected and enlarged, if necessary, which is completed best by cutting back the coronary sinus into the left atrium. Tricuspid valve repair is also performed as needed.

The advantage of the hemi-Fontan is that it shortens the length of time of CPB and dissection required for the completion Fontan procedure, which requires only the removal of the intra-atrial patch and placement of a lateral tunnel in the right atrium from the IVC to the SVC. In addition, routine augmentation of the branch pulmonary arteries helps optimize the anatomy for the completion Fontan procedure.

Third-stage palliation: Fontan procedure

The completion Fontan procedure is usually performed in children aged 18-24 months. The infant is evaluated using cardiac catheterization prior to surgery. The Fontan technique used by the authors for HLHS anatomy is the technique termed total cavopulmonary connection with a lateral tunnel. After achieving CPB, the right atrium is opened.

If a hemi-Fontan procedure has been performed, the intra-atrial baffle is resected. In bidirectional Glenn anastomosis, a right atrium–to–pulmonary artery anastomosis is created. A baffle of polytetrafluoroethylene is fashioned and placed inside of the right atrium to convey the IVC return to the cavopulmonary connection (see Media file 5). This technique minimizes the possibility of obstruction of the pulmonary venous return, which can be caused by an atriopulmonary anastomosis. Fenestration of the baffle may help prevent complications in high-risk patients and shorten the period of pleural drainage. Some centers opt for an extracardiac, instead of an intracardiac, lateral tunnel Fontan.

Postoperative Details

First-stage palliation: Norwood procedure

After weaning from CPB, an atrial-monitoring catheter is placed to measure central venous pressure, and infusion of inotropes is initiated. University of Michigan medical staff routinely use continuous infusions of milrinone and low-dose dopamine, adding epinephrine in doses of 0.02-0.06 mcg/kg/min if hypotension is significant. Ventilation, with an initial FIO₂ of 100% to achieve a PCO₂ of approximately 35 mm Hg, is initiated and adjusted depending on the systemic arterial oxygen saturation and the systemic perfusion. If poor peripheral perfusion with systemic saturation in excess of 80-85% is noted, the FIO₂ and minute ventilation are decreased to avoid excess pulmonary vasodilatation. The opposite maneuvers are used if systemic oxygen saturation is less than 70-75%.

Postoperative management is aimed at maintaining the delicate balance between the systemic and pulmonary vascular resistances and, therefore, relative systemic and pulmonary blood flow. Many regimens of ventilation, inotropic support, and vasodilatory support have been used, and multiple indicators of perfusion adequacy (mixed venous oxygen, lactate) have been measured with varying degrees of success.

Ideally, systemic arterial saturation should be maintained at 75-80%, which usually indicates that an optimal pulmonary-to-systemic blood flow ratio of less than 1 has been achieved. However, measurements of mixed venous oxygen saturation and pulmonary venous oxygen saturation are necessary to accurately assess the ratio of pulmonary blood flow (Qp) to systemic blood flow (Qs). The authors have found that serial lactate measurements provide an excellent indication of low cardiac output, and they rely on these determinations rather than mixed venous oxygen saturations.

Second- and third-stage palliation: Hemi-Fontan and Fontan procedures

For second- and third-stage operations, maintaining a low pulmonary vascular resistance is paramount. The pulmonary blood flow no longer is driven by an arterial shunt (or systemic RV, in cases of Sano modification), but by central venous pressure. Hypoxia and acidosis, which increase pulmonary vascular resistance, are avoided. Although mild respiratory alkalosis may be beneficial for pulmonary vascular resistance, a pH higher than 7.45-7.5 decreases cerebral blood flow and, hence, SVC return. After the hemi-Fontan procedure is performed, this decrease in SVC return decreases pulmonary blood flow. Inhaled nitrous oxide (NO) may also be used to decrease pulmonary vascular resistance but is infrequently needed.

Follow-up

After discharge from the hospital, regular cardiovascular evaluations are important. The child should be carefully observed for aortic arch obstruction, tricuspid insufficiency, and increasing cyanosis secondary to a limited atrial septal defect, shunt stenosis, or pulmonary artery distortion. For other long-term concerns, see Complications and Outcomes and Prognosis.

Complications

Complications that result from a procedure of the magnitude of the Norwood palliation are fairly common. Complications may include bleeding, low cardiac output syndrome, and arrhythmia in the immediate postoperative period. Aggressive correction of thrombocytopenia and coagulation factors is warranted. Poor peripheral and end-organ perfusion may represent poor cardiac output or pulmonary overcirculation, which may be treated by inotropic support or manipulation of relative pulmonary and systemic resistances. Common arrhythmias include junctional ectopic tachycardiac, which can be treated either with surface cooling to 35-36°C and pacing or with amiodarone infusion.

Incidence of unexplained sudden death, both in the immediate postoperative period and after discharge, remains problematic. In the postoperative period, the authors found that serial serum lactate determinations demonstrating failure to clear lactic acidosis have been helpful in predicting patients who will do poorly despite an apparently stable clinical condition.

Shunt complications, such as thrombosis, can occur. All patients are started on low-dose aspirin when they begin enteral nutrition. Other causes of increasing cyanosis during the postoperative period include pulmonary artery stenosis or distortion and restriction at the level of the atrial septal defect.

Evaluation prior to the hemi-Fontan procedure may reveal pulmonary artery stenosis, particularly of the left branch or at the insertion of the shunt. These stenoses are managed with patch augmentation during the hemi-Fontan procedure. Residual coarctation should be rare if the initial homograft patch is brought sufficiently onto the descending aorta during the Norwood procedure. Postoperative coarctation can usually be managed with balloon dilatation or, if necessary, surgical augmentation.

Long-term complications following the Fontan operation include atrial arrhythmia, thromboembolic events, and protein-losing enteropathy. Atrial arrhythmias are less common with the current techniques of cavopulmonary connections and may be treated with standard antiarrhythmic therapy. All of the authors' patients who undergo the Fontan procedure are maintained on aspirin therapy, whereas others have advocated low-dose warfarin as prophylaxis against thromboembolism. Patients in whom the classic atriopulmonary connection Fontan procedure is performed with a dilated right atrium may benefit from conversion to a lateral tunnel or extracardiac Fontan operation to treat both arrhythmia and thrombosis.

Protein-losing enteropathy remains a difficult problem, affecting as many as 5% of patients who undergo the Fontan procedure. Treatment with intravenous infusions of albumin and immunoglobulin are supportive but not curative. Several other methods, including intravenous heparin, Fontan takedown, and cardiac transplantation, have been used with varying success.

Outcome and Prognosis

First-stage palliation

Bove et al at the University of Michigan studied first-stage palliation of hypoplastic left heart syndrome (HLHS) from January 1990 to August 1995 in 158 patients.¹³ All patients had classic HLHS, defined as right ventricle–dependent circulation, in association with atresia or severe hypoplasia of the aortic valve. Patients were subdivided into a standard-risk (n=127) population and a high-risk (n=31) population. High-risk patients included those undergoing the Norwood procedure after age 1 month, patients with severe obstruction to pulmonary venous return, and patients with significant noncardiac congenital conditions (ie, prematurity, low birth weight, chromosomal anomalies).

Hospital survivors numbered 120 (76%). The hospital survival rate was significantly better in the 127 standard-risk patients (86%) than in the high-risk group (42%). The risk factor analysis failed to reveal any effect on outcome by the morphologic subgroup, ascending aorta size, shunt size, initial pH at hospital presentation, or duration of circulatory arrest.

Among 151 patients at The Children's Hospital of Philadelphia in a report by Norwood et al, 42 (28%) early deaths and 9 (5%) late deaths occurred.¹⁴ In a Children's Hospital Boston series reported by Jonas et al, 78 neonates underwent palliative reconstructive surgery from 1983-1991.¹⁵ Hospital deaths numbered 29 (37%). Analysis of deaths revealed a greater risk of hospital death for infants with aortic atresia and mitral atresia, especially those with ascending aortic dimensions of less than 2 mm. However, in the authors' experience, these conditions have not been associated with increased risk.

The results for the hospital survival for the Norwood procedure has continued to improve. In 2002, Tweddell and colleagues reported a 93% hospital survival in 81 patients undergoing a Norwood procedure for HLHS.¹⁶

Second-stage palliation

Hospital records of 114 patients undergoing the hemi-Fontan procedure for HLHS between August 1993 and April 1998 at the University of Michigan Medical Center were reviewed by Douglas et al.¹⁷ The overall hospital survival rate was 98% (112 patients). Sinus rhythm was present in 92% of patients. At the time of publication, 79 of the patients had undergone the completion Fontan procedure, with 74 survivors (94%). A similar study by Forbess et al from the Children's Hospital Boston also revealed that a cavopulmonary anastomosis performed as a second-stage procedure for HLHS reduced mortality and improved intermediate survival rates.¹⁸

Third-stage palliation

One hundred consecutive patients with classic HLHS underwent a Fontan procedure at the University of Michigan between February 1992 and April 1998.¹⁹ The survival rate in patients (n=52) undergoing surgery in the second half of the study and treated with a prior hemi-Fontan procedure at second-stage palliation was 98%. No deaths have occurred in patients undergoing the last 125 consecutive Fontan procedures for HLHS. Several other centers also have reported significant improvements in survival rates following the Fontan procedure in patients with HLHS.

Neurodevelopmental outcomes

As survivals have improved, other endpoints, such as patient neurodevelopmental outcome, have become of increasing interest to the healthcare provider caring for the patient with HLHS. Similar to any patient with cyanotic congenital heart disease, patients with HLHS are at risk for neurodevelopmental delay for multiple reasons. Cyanosis, congestive heart failure, and CNS abnormalities are associated with HLHS and can contribute to developmental delay. In addition, CPB and hypothermic circulatory arrest at the time of repair can cause neurologic injury.

In a recent study from the University of Michigan Medical Center, Goldberg and colleagues evaluated 51 patients with single ventricle physiology, 26 patients with HLHS, and 25 patients with other cardiac anomalies.²⁰ The primary testing methods were the Wechsler Preschool and Primary Scales of Intelligence, revised for children aged 34-87 months, and the Wechsler Intelligence Scale, third edition, for children aged 72 months to 17 years. Additional tests included the Bayley Scales of Infant Development, the Vineland Adaptive Behavior Scales, and the Child Behavior Checklist.

Results indicated that children with HLHS scored statistically lower than children without HLHS with single ventricles. However, neither group scored significantly differently than population standards. As has been seen in children with congenital heart disease in general, patients in this study scored significantly better on tests of verbal intelligence than on tests of motor skills. Socioeconomic status, hypothermic circulatory arrest, and perioperative seizures were significant risk factors for impaired neurodevelopmental outcome. Duration of CPB, cardiac arrest requiring resuscitation, and clinical shock or pH less than 7.1 did not correlate with a poor neurodevelopmental result.

Future and Controversies

Several groups have begun to use the techniques of regional cerebral perfusion for aortic arch reconstruction in lieu of deep hypothermic circulatory arrest. For this technique, the proximal anastomosis of the modified Blalock-Taussig shunt is performed prior to arresting the heart. Then, the arterial cannula can be placed into the shunt, and perfusion is administered to the innominate artery. Whether these techniques will improve perioperative survival rates or long-term neurodevelopmental outcomes has yet to be determined. Several recent abstracts have failed to demonstrate any improvement in outcome with regional cerebral perfusion.

Currently, numerous groups are advocating the use of an extracardiac conduit to complete the Fontan procedure. This technique may offer significant advantages; however, patients may be exposed to the risks of thromboembolic complications inherent in prosthetic conduits in the venous system. Lack of growth is also of concern. The literature does not have a consensus that favors one technique over the other.

Future considerations for the Fontan procedure in this subgroup of patients include minimization of thromboembolic events, preservation of right ventricular and tricuspid valve function, and prevention of arrhythmias.

Multimedia

Media file 1: The main pulmonary artery and ductus arteriosus have been divided. Dashes indicate the line of incision on the hypoplastic ascending aorta. Image courtesy of Edward L. Bove, MD.

Media file 2: The ascending aorta is opened and sutured to the adjacent proximal main pulmonary artery. A patch of pulmonary homograft is fashioned to create the neoaorta (inset). Image courtesy of Edward L. Bove, MD.

Media file 3: Completed Norwood procedure showing reconstructed neoaorta and modified Blalock-Taussig shunt from the innominate artery to the confluence of the branch pulmonary arteries. Image courtesy of Edward L. Bove, MD.

Media file 4: Hemi-Fontan procedure. The modified Blalock-Taussig shunt is ligated, and incisions are made in the right atrial appendage and pulmonary arteries (upper left). The posterior aspect of the right atriotomy is anastomosed to the inferior aspect of the pulmonary arteriotomy (upper right). A patch of polytetrafluoroethylene is placed to prevent the superior vena cava return from entering the right atrium. The cavopulmonary connection is roofed with a patch of pulmonary homograft (lower). Image courtesy of Koji Kagasaki, MD.

Media file 5: Fontan procedure. Through a right atriotomy, the polytetrafluoroethylene (PTFE) patch has been removed. A new PTFE patch is placed to baffle the inferior vena cava return to the cavopulmonary connection constructed during the hemi-Fontan procedure (left). The arrows indicate the systemic venous return bypassing the right heart to directly enter the pulmonary arteries (right). Image courtesy of Edward L. Bove, MD.

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Keywords

hypoplastic left heart syndrome, staged Norwood procedure, HLHS, left ventricular hypoplasia, absence of left ventricle, ascending aorta hypoplasia, staged orthoterminal correction, cardiac anomaly, cardiac disease, cardiac surgery, heart surgery, heart disease, orthotopic cardiac transplantation, cardiac transplantation, staged reconstructive cardiac surgery, right ventricle–to–pulmonary artery conduit, RVPAC, heart transplantation, aortic atresia, mitral atresia, congenital heart disease, patent ductus arteriosus, metabolic acidosis, renal failure, aortic stenosis, mitral stenosis, tricuspid regurgitation, cardiomegaly, obstructed pulmonary venous return, atrial septal defect, Fontan procedure

Contributor Information and Disclosures

Author

Richard G Ohye, MD, Director, Pediatric Cardiac Transplantation, Fellowship Program Director, Pediatric Cardiac Surgery, Assistant Professor, Department of Surgery, Section of Cardiac Surgery, University of Michigan Medical Center
Richard G Ohye, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Cardiology, American College of Chest Physicians, American College of Surgeons, Association for Academic Surgery, International Society for Heart and Lung Transplantation, and Society of Thoracic Surgeons
Disclosure: Nothing to disclose.

Coauthor(s)

Ralph S Mosca, MD, Director, Pediatric Cardiac Surgery, Associate Professor, Department of Surgery, New York Presbyterian Medical Center
Ralph S Mosca, MD is a member of the following medical societies: American College of Surgeons, Central Surgical Association, Congenital Heart Surgeons Society, International Society for Heart and Lung Transplantation, Michigan State Medical Society, and Society of Thoracic Surgeons
Disclosure: Nothing to disclose.

Edward L Bove, MD, Associate Director, PICU, CS Mott Children's Hospital; Director, Department of Surgery, Section of Thoracic Surgery, Division of Pediatric Cardiovascular Surgery, Professor, University of Michigan Medical Center
Edward L Bove, MD is a member of the following medical societies: American Association for Thoracic Surgery, American College of Cardiology, American College of Chest Physicians, American College of Surgeons, American Heart Association, American Medical Association, American Surgical Association, Central Surgical Association, Congenital Heart Surgeons Society, Medical Society of the State of New York, Society of Thoracic Surgeons, and Society of University Surgeons
Disclosure: Nothing to disclose.

Medical Editor

Jonah Odim, MD, PhD, MBA, Senior Medical Officer, Transplantation Immunology Branch, Division of Allergy, Immunology, and Transplantation, National Institute of Allergy and Infectious Diseases, National Institutes of Health
Jonah Odim, MD, PhD, MBA is a member of the following medical societies: American College of Cardiology, American College of Chest Physicians, American College of Physician Executives, American College of Surgeons, American Heart Association, American Society for Artificial Internal Organs, American Society of Transplant Surgeons, Association for Academic Surgery, Association for Surgical Education, Canadian Cardiovascular Society, International Society for Heart and Lung Transplantation, National Medical Association, New York Academy of Sciences, Royal College of Physicians and Surgeons of Canada, Society of Critical Care Medicine, and Society of Thoracic Surgeons
Disclosure: Nothing to disclose.

Pharmacy Editor

Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine.com, Inc
Disclosure: Pfizer Inc Stock Investment from broker recommendation; Avanir Pharma Stock Investment from broker recommendation

Managing Editor

Mary C Mancini, MD, PhD, Professor, Department of Surgery, Louisiana State University Health Sciences Center
Mary C Mancini, MD, PhD is a member of the following medical societies: American Heart Association, American Medical Association, American Thoracic Society, Association for Academic Surgery, Association for Surgical Education, International College of Surgeons, International Society for Heart and Lung Transplantation, New York Academy of Sciences, Phi Beta Kappa, and Southern Thoracic Surgical Association
Disclosure: Nothing to disclose.

CME Editor

Daniel Rauch, MD, FAAP, Director, Pediatric Hospitalist Program, Associate Professor, Department of Pediatrics, New York University School of Medicine
Daniel Rauch, MD, FAAP is a member of the following medical societies: Ambulatory Pediatric Association, American Academy of Pediatrics, and Society of Hospital Medicine
Disclosure: Baxter Honoraria Consulting; Pfizer Honoraria Consulting

Chief Editor

Stuart Berger, MD, Professor of Pediatrics, Division of Cardiology, Medical College of Wisconsin; Chief of Pediatric Cardiology, Medical Director of Pediatric Heart Transplant Program, Medical Director of The Heart Center, Children's Hospital of Wisconsin
Stuart Berger, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology, American College of Chest Physicians, American Heart Association, and Society for Cardiac Angiography and Interventions
Disclosure: Nothing to disclose.

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