Hypoplastic left heart syndrome

Hypoplastic left heart syndrome (also known as HLHS), is a rare congenital heart defect in which the left side of the heart is severely underdeveloped.

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Causes

While many authorities believe the cause of HLHS is unknown [1], [2], [3] recent research indicates that HLHS may be caused due to genetic factors. [4], [5]

Presentation

In babies with HLHS, the aorta and left ventricle are very small, and the aortic and mitral valves are either too small to allow sufficient blood flow or are atretic (closed) altogether. As blood returns from the lungs to the left atrium, it must pass through an atrial septal defect to the right side of the heart.

In a healthy human, the left side of the heart receives oxygen-rich blood from the lungs and pumps it out to the rest of the body; with these structures underdeveloped, they cannot circulate blood to other organs, and the right ventricle must pump blood to both the lungs, as it would normally, and to the rest of the body, a situation which cannot be sustained for long.

In cases of HLHS, the right side of the heart often must pump blood to the body through a patent ductus arteriosus. As the ductus arteriosus usually closes within eleven days after birth, blood flow is severely restricted and eventually cut off, leading to dangerously low circulation and eventually to shock.

Treatment

Without treatment, HLHS is fatal, but with intervention, an infant may survive. A pediatric cardiothoracic surgeon may perform a series of operations or a full heart transplant. In the meantime, the ductus may be kept open to allow bloodflow using medication containing prostaglandin. Because these operations are complex and need to be individualized for each patient, a cardiologist must assess all medical and surgical options on a case-by-case basis.

The two methods for treatment of HLHS are transplantation and a 3-stage surgical procedure.

The 3-stage procedure is a palliative procedure (not a cure), as the child's circulation is made to work with only two of the heart's four chambers.

• The first step is the Norwood procedure or the Sano shunt. The first step makes the right ventricle pump blood to the whole body (which the left ventricle normally does) AND to the lungs. During this time the baby may be medically fragile and have feeding problems because the heart is working very hard.

• The second stage, the bi-directional Glenn or Hemi-Fontan, allows greater blood flow to the upper body and reduces some of the workload from the right ventricle.

• The final procedure, the Fontan (Fontan procedure) allows blood to automatically flow to the lungs (rather than being pumped there) and allows the right ventricle to only pump blood out to the body. The blood travels passively to the lungs because of the blood pressure throughout the body.

The Norwood Procedure is generally performed within a week of birth, the second stage at 3-6 months of age, and the Fontan at 18 months to 4 years of age. There are two types of Fontan: the Lateral Tunnel Fontan, and the Extracardiac Fontan. When the Fontan Procedure was first being done for children with HLHS, the only Fontan was the Lateral Tunnel Fontan. This requires actual cutting in the heart itself to create a "tunnel" by which the blood can travel passively to the lungs. Within the last decade, doctors have created an Extracardiac Fontan. This operation creates a tunnel outside the heart itself which reduces the chances of Fontan patients developing scar tissue on the heart which might later cause arrythmias.

Prognosis

While infants successfully treated for HLHS have a good chance of survival, they may experience chronic health problems for the rest of their lives. The 3-stage surgeries were developed in the early 1980's with no survivors prior to that time. Therefore, the earliest survivors are in their early 20's and the long term prognosis is unknown. However, the advances in surgical and medical techniques have helped increase the survival rate dramatically since the surgeries were first developed.

As is true for patients with other types of heart defects involving malformed valves,^[1] HLHS patients run a high risk of endocarditis, and must be monitored by a cardiologist for the rest of their lives to check on their heart function.

References

• 1 "Hypoplastic Left Heart Syndrome: Causes" Copyright ©2001-2007 Mayo Foundation for Medical Education and Research.

• 2 "Hypoplastic Left Heart Syndrome" eMedicine by WebMD, August 15, 2006.

• 3 "Hypoplastic Left Heart Syndrome" MedLinePlus a service of the U.S. National Library of Medicine and the National Institutes of Health. Updated by Anne J. L. Chun, M.D., Assistant Professor of Pediatrics, Division of Pediatric Cardiology, New York University School of Medicine, New York, NY. Review provided by VeriMed Healthcare Network, 5-30-06.

• 4 "Hypoplastic left heart syndrome likely caused by genetic factors" Medical Condition News, 11-Oct-2007.

• 5 "Identification of connexin43 (alpha1) gap junction gene mutations in patients with hypoplastic left heart syndrome by denaturing gradient gel electrophoresis (DGGE)" Dasgupta C, Martinez AM, Zuppan CW, Shah MM, Bailey LL, Fletcher WH. Mutation Research 2001 Aug 8;479(1-2):173-86.

• Congenital Heart Defects.com http://www.congenitalheartdefects.com - the most comprehensive site on the Internet for congenital heart defect information

• Hypoplastic Left Heart Syndrome information from Seattle Children's Hospital Heart Center

• HLHS Information Page - created for parents expecting a child with HLHS. Includes questions to ask the physicians and insurance company. at homestead.com

• Card-AG, The Cardiologycal Working Group of the University Pediatric Clinic Munster

• Hypoplastic Left Heart Syndrome, American Heart Association

• Overview at Cincinnati Children's Hospital Medical Center

• Overview at University of Michigan Congenital Heart Center