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

Hypoplastic Left Heart Syndrome and the Staged Norwood Procedure

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
Coauthor(s): 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
Contributor Information and Disclosures

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.

More on Hypoplastic Left Heart Syndrome and the Staged Norwood Procedure

Overview: Hypoplastic Left Heart Syndrome and the Staged Norwood Procedure
Workup: Hypoplastic Left Heart Syndrome and the Staged Norwood Procedure
Treatment: Hypoplastic Left Heart Syndrome and the Staged Norwood Procedure
Follow-up: Hypoplastic Left Heart Syndrome and the Staged Norwood Procedure
Multimedia: Hypoplastic Left Heart Syndrome and the Staged Norwood Procedure
References
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References

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Further Reading

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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

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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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