Hypoplastic left heart syndrome
Encyclopedia
Hypoplastic left heart syndrome (also known as HLHS), is a rare congenital heart defect
in which the left ventricle of the heart
is severely underdeveloped.
There is evidence associating it with Gap junction protein, alpha 1
.
Colleagues at Cincinnati Children’s Hospital in Ohio studied 1,500 newborns from 38 children’s hospitals in the United States from the 1990s to 2006. They found that babies born between April and July were more likely to have this defect, establishing strong evidence that seasonality and environmental factors play a significant role in causation. PMID: 20817208
and left ventricle
are underdeveloped before birth, and the aortic
and mitral valve
s are either too small to allow sufficient blood flow or are atretic (closed) altogether. As blood
returns from the lung
s 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 cutoff, leading to dangerously low circulation and eventually to shock.
. 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.
Currently, infants who undergo either the staged reconstructive surgery (Norwood procedure
almost immediately after birth, Glenn procedure
at 3 to 6 months of age, and the Fontan procedure
at 3 to 5 years of age) or who undergo cardiac transplantation have a 5-year survival of approximately 50-60% as a group. However, it is becoming clear that there are higher risk subsets where 5 year survival is lower (including those with lower birth weight,additional congenital anomalies, a genetic syndrome or those with a highly restrictive atrial septum. For patients without these additional risk factors, 5 year survival now approaches 80%. Further, studies show that about 50% of those children who survived surgery in the early development of staged reconstruction have developmental delay or need special education; about 25% of these surgical survivors have severe disabilities. There is growing evidence that while the incidence of developmental and behavioral disabilities continues to be higher than that in the general population, children operated upon in the more current era have shown significantly better neurological outcomes. An alternative to the traditional Norwood is the Hybrid procedure.
Some parents choose an option referred to as compassionate care, and these infants receive treatment aimed at relieving suffering without extending life. Compassionate care is overseen by a physician, and may be carried out either in the hospital or at home. Studies show that when presented with all options, about half of parents choose life-prolonging interventions and half choose compassionate care. A study in 2003 concluded that a selection of physicians who are experts in the care of children with HLHS were evenly split when asked what they would do if their own children were born with HLHS, with 1/3 stating that they would choose surgery, 1/3 stating that they would choose palliative (compassionate) treatment without surgery, and 1/3 stating that they are uncertain which choice they would make.
The three-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.
. In this procedure, the right ventricle is used to pump blood into the systemic circulation. Since the right ventricle is no longer directly pumping blood to the lungs, a shunt is required in order to pass deoxygenated blood through the lungs. Either the subclavian artery can be connected to the pulmonary circulation (Blalock-Taussig shunt), or a shunt is made directly from the right ventricle to the pulmonary circulation (Sano shunt). The narrow aorta is enlarged using a patch to improve blood flow to the body.
http://hlhs-awareness-uk.com/images/new%20norwood.gif
During this time the baby may be medically fragile and have feeding problems because the heart is working very hard. There is a considerable degree of venous mixing in the right ventricle, leading to lower oxygenation saturation. In addition, the Blalock-Taussig shunt and the Sano shunt both expose the lungs to systemic arterial pressures, leading in the long term to pulmonary hypertension and eventually to heart failure.
Hybrid (Sano) procedure
The Hybrid procedure is used in place of the Norwood. The Hybrid procedure does not necessitate the use of heart-lung bypass or performing a sternotomy
. Instead of a six-hour surgery, the Hybrid typically takes one to two hours. In the procedure, a stent is placed in the Ductus Arteriosis to maintain its patency, and the Pulmonary Artery has a band placed over it to limit over-circulation to the lungs. Outcomes with the Hybrid approach are comparable with the Norwood.
http://www.miothospitals.com/images/news/at_miot/hybrid_norwood/3.jpg
) relieves some of the above problems. In this operation, the superior vena cava is ligated from the heart and connected to the pulmonary circulation. At this time, the Blalock-Taussig or Sano shunt is taken down. At this point, the lungs are no longer exposed to systemic arterial pressures, but much lower venous pressures. Although venous blood from the upper half of the body is no longer mixing with oxygenated blood in the right ventricle, there is still venous mixing from the lower half of the body, leading to some degree of oxygen desaturation.
During this time the child may have improved quality of life as the heart does not have to work as hard.
http://www.severinbrenny.com/bidirectionalglenn.jpg
) completes the repair of the hypoplastic left heart. Although there are several variations, the functional effect is to redirect venous blood from the lower body (through the inferior vena cava) away from the right atrium to the pulmonary artery. Now, there should not be any mixing of oxygenated and deoxygenated blood in the right ventricle. The right ventricle performs the traditional job of the left, supplying the body with oxygenated blood, while the passive systemic venous pressure performs the traditional job of the right, passing deoxygenated blood to the lungs.
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 four 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 arrhythmias.
As is true for patients with other types of heart defects involving malformed valves, 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.
The three stage Norwood procedure only increases the life of the heart as HLHS cannot be cured. The child may need a heart transplant at some point in the child's lifetime.
There is an extensive network of parents and children who have experienced this problem, and a number of targeted small press publications and websites.
Patients receiving the Fontan Procedure have an increased incidence of "Plastic Bronchitis."
Congenital heart defect
A congenital heart defect is a defect in the structure of the heart and great vessels which is present at birth. Many types of heart defects exist, most of which either obstruct blood flow in the heart or vessels near it, or cause blood to flow through the heart in an abnormal pattern. Other...
in which the left ventricle of the heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
is severely underdeveloped.
Causes
If part of the endocardial tube gets pinched shut in a region that becomes the future ventricle, hypoplastic heart syndrome will occur. If the pinched part of the endocardial tube is the bulbus-cordis region of the developing heart, hypoplastic RIGHT syndrome will occur. If it is in the ventricle region it will be the LEFT side that is hypoplastic.There is evidence associating it with Gap junction protein, alpha 1
Gap junction protein, alpha 1
-Interactions:Gap junction protein, alpha 1 has been shown to interact with MAPK7, Caveolin 1, Tight junction protein 1 CSNK1D, and PTPmu .-Further reading:...
.
Colleagues at Cincinnati Children’s Hospital in Ohio studied 1,500 newborns from 38 children’s hospitals in the United States from the 1990s to 2006. They found that babies born between April and July were more likely to have this defect, establishing strong evidence that seasonality and environmental factors play a significant role in causation. PMID: 20817208
Presentation
In babies with HLHS, the aortaAorta
The aorta is the largest artery in the body, originating from the left ventricle of the heart and extending down to the abdomen, where it branches off into two smaller arteries...
and left ventricle
Left ventricle
The left ventricle is one of four chambers in the human heart. It receives oxygenated blood from the left atrium via the mitral valve, and pumps it into the aorta via the aortic valve.-Shape:...
are underdeveloped before birth, and the aortic
Aortic valve
The aortic valve is one of the valves of the heart. It is normally tricuspid , although in 1% of the population it is found to be congenitally bicuspid . It lies between the left ventricle and the aorta....
and mitral valve
Mitral valve
The mitral valve is a dual-flap valve in the heart that lies between the left atrium and the left ventricle...
s are either too small to allow sufficient blood flow or are atretic (closed) altogether. As blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
returns from the lung
Lung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...
s to the left atrium
Left atrium
The left atrium is one of the four chambers in the human heart. It receives oxygenated blood from the pulmonary veins, and pumps it into the left ventricle, via the mitral valve.-Foramen ovale:...
, it must pass through an atrial septal defect
Atrial septal defect
Atrial septal defect is a form of congenital heart defect that enables blood flow between the left and right atria via the interatrial septum. The interatrial septum is the tissue that divides the right and left atria...
to the right side of the heart.
In a healthy human, the left side of the heart receives oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
-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
Patent ductus arteriosus
Patent ductus arteriosus is a congenital disorder in the heart wherein a neonate's ductus arteriosus fails to close after birth. Early symptoms are uncommon, but in the first year of life include increased work of breathing and poor weight gain...
ductus arteriosus
Ductus arteriosus
In the developing fetus, the ductus arteriosus , also called the ductus Botalli, is a shunt connecting the pulmonary artery to the aortic arch. It allows most of the blood from the right ventricle to bypass the fetus's fluid-filled lungs. Upon closure at birth, it becomes the ligamentum arteriosum...
. As the ductus arteriosus usually closes within eleven days after birth, blood flow is severely restricted and eventually cutoff, leading to dangerously low circulation and eventually to shock.
Treatment
Without life-prolonging interventions, 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 blood-flow using medication containing prostaglandinProstaglandin
A prostaglandin is any member of a group of lipid compounds that are derived enzymatically from fatty acids and have important functions in the animal body. Every prostaglandin contains 20 carbon atoms, including a 5-carbon ring....
. 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.
Currently, infants who undergo either the staged reconstructive surgery (Norwood procedure
Norwood procedure
The Norwood Procedure is a surgery performed on the heart, the first successful use of the procedure was reported by Norwood and colleagues in 1981.Cardiopulmonary bypass is required.-Indications:...
almost immediately after birth, Glenn procedure
Glenn procedure
Glenn procedure is a palliative surgical procedure performed for patients with Tricuspid atresia. This procedure is largely replaced by Bidirectional Glenn procedure .It connects the SVC to the right PA....
at 3 to 6 months of age, and the Fontan procedure
Fontan procedure
The Fontan procedure, or Fontan/Kreutzer procedure, is a palliative surgical procedure used in children with complex congenital heart defects. It involves diverting the venous blood from the right atrium to the pulmonary arteries without passing through the morphologic pulmonary ventricle...
at 3 to 5 years of age) or who undergo cardiac transplantation have a 5-year survival of approximately 50-60% as a group. However, it is becoming clear that there are higher risk subsets where 5 year survival is lower (including those with lower birth weight,additional congenital anomalies, a genetic syndrome or those with a highly restrictive atrial septum. For patients without these additional risk factors, 5 year survival now approaches 80%. Further, studies show that about 50% of those children who survived surgery in the early development of staged reconstruction have developmental delay or need special education; about 25% of these surgical survivors have severe disabilities. There is growing evidence that while the incidence of developmental and behavioral disabilities continues to be higher than that in the general population, children operated upon in the more current era have shown significantly better neurological outcomes. An alternative to the traditional Norwood is the Hybrid procedure.
Some parents choose an option referred to as compassionate care, and these infants receive treatment aimed at relieving suffering without extending life. Compassionate care is overseen by a physician, and may be carried out either in the hospital or at home. Studies show that when presented with all options, about half of parents choose life-prolonging interventions and half choose compassionate care. A study in 2003 concluded that a selection of physicians who are experts in the care of children with HLHS were evenly split when asked what they would do if their own children were born with HLHS, with 1/3 stating that they would choose surgery, 1/3 stating that they would choose palliative (compassionate) treatment without surgery, and 1/3 stating that they are uncertain which choice they would make.
The three-stage procedure is a palliative
Palliative care
Palliative care is a specialized area of healthcare that focuses on relieving and preventing the suffering of patients...
procedure (not a cure), as the child's circulation is made to work with only two of the heart's four chambers.
Step 1: Norwood procedure
The first step is the Norwood procedureNorwood procedure
The Norwood Procedure is a surgery performed on the heart, the first successful use of the procedure was reported by Norwood and colleagues in 1981.Cardiopulmonary bypass is required.-Indications:...
. In this procedure, the right ventricle is used to pump blood into the systemic circulation. Since the right ventricle is no longer directly pumping blood to the lungs, a shunt is required in order to pass deoxygenated blood through the lungs. Either the subclavian artery can be connected to the pulmonary circulation (Blalock-Taussig shunt), or a shunt is made directly from the right ventricle to the pulmonary circulation (Sano shunt). The narrow aorta is enlarged using a patch to improve blood flow to the body.
http://hlhs-awareness-uk.com/images/new%20norwood.gif
During this time the baby may be medically fragile and have feeding problems because the heart is working very hard. There is a considerable degree of venous mixing in the right ventricle, leading to lower oxygenation saturation. In addition, the Blalock-Taussig shunt and the Sano shunt both expose the lungs to systemic arterial pressures, leading in the long term to pulmonary hypertension and eventually to heart failure.
Hybrid (Sano) procedure
The Hybrid procedure is used in place of the Norwood. The Hybrid procedure does not necessitate the use of heart-lung bypass or performing a sternotomy
Median sternotomy
Median sternotomy is a type of surgical procedure in which a vertical inline incision is made along the sternum, after which the sternum itself is divided, or "cracked"...
. Instead of a six-hour surgery, the Hybrid typically takes one to two hours. In the procedure, a stent is placed in the Ductus Arteriosis to maintain its patency, and the Pulmonary Artery has a band placed over it to limit over-circulation to the lungs. Outcomes with the Hybrid approach are comparable with the Norwood.
http://www.miothospitals.com/images/news/at_miot/hybrid_norwood/3.jpg
Step 2: Glenn procedure
The second stage, the bi-directional Glenn procedure or Hemi-Fontan (see also Kawashima procedureKawashima procedure
The Kawashima procedure is used for congenital heart disease with a single effective ventricle and an interrupted inferior vena cava . It was first performed in 1978 and reported in 1984.-Procedure:...
) relieves some of the above problems. In this operation, the superior vena cava is ligated from the heart and connected to the pulmonary circulation. At this time, the Blalock-Taussig or Sano shunt is taken down. At this point, the lungs are no longer exposed to systemic arterial pressures, but much lower venous pressures. Although venous blood from the upper half of the body is no longer mixing with oxygenated blood in the right ventricle, there is still venous mixing from the lower half of the body, leading to some degree of oxygen desaturation.
During this time the child may have improved quality of life as the heart does not have to work as hard.
http://www.severinbrenny.com/bidirectionalglenn.jpg
Step 3: Fontan procedure
The final procedure, the Fontan (Fontan procedureFontan procedure
The Fontan procedure, or Fontan/Kreutzer procedure, is a palliative surgical procedure used in children with complex congenital heart defects. It involves diverting the venous blood from the right atrium to the pulmonary arteries without passing through the morphologic pulmonary ventricle...
) completes the repair of the hypoplastic left heart. Although there are several variations, the functional effect is to redirect venous blood from the lower body (through the inferior vena cava) away from the right atrium to the pulmonary artery. Now, there should not be any mixing of oxygenated and deoxygenated blood in the right ventricle. The right ventricle performs the traditional job of the left, supplying the body with oxygenated blood, while the passive systemic venous pressure performs the traditional job of the right, passing deoxygenated blood to the lungs.
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 four 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 arrhythmias.
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 1980s with no survivors prior to that time. Therefore, the earliest survivors are in their mid 20s 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, HLHS patients run a high risk of endocarditis
Endocarditis
Endocarditis is an inflammation of the inner layer of the heart, the endocardium. It usually involves the heart valves . Other structures that may be involved include the interventricular septum, the chordae tendineae, the mural endocardium, or even on intracardiac devices...
, and must be monitored by a cardiologist for the rest of their lives to check on their heart function.
The three stage Norwood procedure only increases the life of the heart as HLHS cannot be cured. The child may need a heart transplant at some point in the child's lifetime.
There is an extensive network of parents and children who have experienced this problem, and a number of targeted small press publications and websites.
Patients receiving the Fontan Procedure have an increased incidence of "Plastic Bronchitis."
External links
- HLHS Information Page Questions to ask medical professionals and insurance company, plus resources
- Hypoplastic Left Heart Syndrome information from Seattle Children's Hospital Heart Center
- Card-AG, The Cardiologycal Working Group of the University Pediatric Clinic Munster
- Hypoplastic Left Heart Syndrome, American Heart AssociationAmerican Heart AssociationThe American Heart Association is a non-profit organization in the United States that fosters appropriate cardiac care in an effort to reduce disability and deaths caused by cardiovascular disease and stroke. It is headquartered in Dallas, Texas...
- Overview at Cincinnati Children's Hospital Medical CenterCincinnati Children's Hospital Medical CenterCincinnati Children's Hospital Medical Center is a 523-bed pediatric hospital located in Cincinnati, Ohio. It is currently ranked the third-best pediatric medical center in the United States by US News and World Report...
- Overview at University of MichiganUniversity of MichiganThe University of Michigan is a public research university located in Ann Arbor, Michigan in the United States. It is the state's oldest university and the flagship campus of the University of Michigan...
Congenital Heart Center - Cardiac Center at The Children's Hospital of Philadelphia
- Little Hearts Matter, a charity providing support and information on HLHS and other single ventricle heart defects
- Baby Hearts Press
- www.congenitalheartdefects.com
- 120+ stories of children born with Hypoplastic Left Heart Syndrome hosted by the The Congenital Heart Information Network.
- HLHS email support groups/discussion list hosted by the The Congenital Heart Information Network (membership required).
- Little Hearts, Inc. - Providing hope with stories of children with HLHS and other CHDs. Email support group (membership required)
- HeartLine, a charity for children with heart conditions and their families
- Designer Heart, A Congenital Heart Defect Network.
- It's My Heart, a non-profit organization created to provide support to and advocating for those affected by Acquired and Congenital Heart Defects.