Hypoplastic left heart syndrome (HLHS)

Hypoplastic left heart syndrome (HLHS) is one of the most challenging congenital heart defects to care for. But Children’s Hospital Boston is a world pioneer in innovative HLHS care—including fetal cardiac intervention—and our team is well-qualified to care for your child.

We are known for our science-driven approach. We’re home to the world’s most extensive pediatric hospital research enterprise and we partner with elite health care and biotech organizations around the globe. But as specialists in innovative, family-centered care, our physicians never forget that your baby is precious, and not just a patient.
 

What characterizes HLHS?

Hypoplastic left heart syndrome is one of several congenital (present at birth) heart defects in which the heart has only one fully functioning ventricle (single ventricle defect).

In HLHS, most of the structures on the left side of the heart are too small and underdeveloped (hypoplastic) to provide enough red blood flow for the body’s needs. The most critical defect in HLHS is the small left ventricle, which needs to be large enough and strong enough to pump blood out to the body. If it’s too small, it simply can’t function effectively.

 Other left heart structures can also be underdeveloped in varying degrees, including:

• the mitral valve, which controls blood flow between the left atrium and left ventricle in the heart
• the aortic valve, which regulates blood flow from the left ventricle or main pumping chamber into the aorta
• the aorta, the largest artery in the body, which supplies oxygen-rich blood to the body and is one of the two great arteries in the heart

In HLHS, despite the severity of the heart defect, the fetus or newborn is able to survive because of two naturally occurring “holes in the heart,” which allow for the communication of blood between the left and right sides of the heart. These are the:

• patent ductus arteriosus (PDA): a blood vessel (the ductus arteriosus) that connects the two great arteries (the aorta and the pulmonary artery) and usually closes soon after birth. As long as the ductus remains open (patent), blood can pass from the right ventricle and pulmonary artery to the aorta and body, allowing some oxygen-rich blood to circulate.
   
• patent foramen ovale (PFO): The foramen ovale is a small opening between the right and left atria, normally present in utero, but which usually closes shortly after birth. With HLHS, it’s important that the foramen ovale stay open (patent) as this allows blood returning from the lungs to cross from the left atrium to the right atrium and out to the body via the right ventricle and pulmonary artery.

In HLHS, blood returning to the right atrium from the lungs must pass through the PFO to reach the right side of the heart. The right ventricle must then do “double duty”—pumping blood to the lungs through the pulmonary artery and to the body through the PDA.

Once the PDA begins to close (a natural occurrence), the baby will become extremely sick (go into “shock”) due to lack of blood supply to the body. At this point, treatment is necessary for the baby to survive.
 

How is HLHS diagnosed?

• prenatal, or fetal, diagnosis: made by fetal ultrasound. When you go for your routine fetal ultrasound, your doctor should be able to identify:
  • a four-chamber heart
  • two valves entering the heart
  • two valves and blood vessels exiting the heart

HLHS can be diagnosed on fetal ultrasound when the person performing the ultrasound notices that the left heart structures are small. If HLHS is suspected, you should be referred to a fetal pediatric cardiologist for a fetal echocardiogram (a specialized fetal cardiac ultrasound).

• postnatal diagnosis: If HLHS wasn’t diagnosed prenatally, HLHS is usually diagnosed after the newborn baby shows signs of distress.
   

What is the value of diagnosing HLHS prenatally?

A diagnosis of HLHS through prenatal cardiac ultrasound enables us to plan to treat your newborn immediately after delivery. The family and medical team should plan for delivery at, or next to, a cardiac center that’s equipped to care for the newborn, such as:

• a children’s hospital with an adult or obstetric hospital attached or very near
• a medical center that has adult/obstetric care, as well as neonatal and pediatric cardiac services
   

What are the symptoms of HLHS?

At first, a newborn with HLHS may appear normal. But symptoms usually develop in the first few hours or days of life. Lack of vital blood flow causes the baby to go into profound shock, endangering the brain, liver, kidneys and other vital organs. Symptoms may include:

• rapid breathing or shortness of breath
• rapid heartbeat or pounding heart
• poor suckling and feeding
• cold extremities (poor perfusion)
• blue color of the skin, lips and nailbeds (cyanosis)
• lethargy
   

How do you treat HLHS?

• fetal cardiac intervention: A small number of prenatally diagnosed fetuses with HLHS may benefit from fetal intervention.

• stabilization and intervention of the newborn: If the diagnosis of HLHS is known before birth, the neonatal and cardiac teams will begin caring for the newborn with HLHS immediately after birth. A few newborns will need to have a procedure to open up a too-small foramen ovale immediately after birth (performed in the cardiac catheterization laboratory), but most will be stable and require mostly close observation in the cardiac intensive care unit.

An intravenous medication called prostaglandin (PGE), to keep the ductus arteriosus from closing, will be started and administered until the surgery.

• staged surgical interventions: All children with HLHS will undergo at least three surgeries within the first three years of life.
  
  There are three variations of the first surgery (“Stage I”). Which variation is used will depend on the surgeon’s preference, the baby’s size, and the exact anatomic features of the heart. These surgical options are:

• the Norwood operation
• the Sano modification
• the hybrid procedure

The second surgery is called the bidirectional-Glenn shunt, and the third is called the Fontan. Together, they make up a series of surgeries called the Fontan Sequence. The goals of these surgeries are to:

• enable the fully-functioning right ventricle to do the work normally done by two ventricles
• separate the blue (low-oxygen-content) blood (pulmonary circulation) from the red (well-oxygenated) blood (systemic circulation)

 For details, see Treatment & care.

Read the story of HLHS patient Parker.
 

Will my child be OK?

Open heart surgery at Children’s has the one of the highest success rates in the United States among large pediatric cardiac centers. However, your child will need at least three staged surgeries in his first few years of life.

Note: Infants who’ve had initial surgery for a single ventricle defect are typically enrolled in Children’s Home Monitoring Program between the baby’s Stage I and Stage II operations in the Fontan sequence. For more, see “Children’s Home Monitoring Program for your child” in Treatment & care.
                              

What about later in life?

Children with hypoplastic left heart syndrome will need follow-up care throughout their lives to ensure that their hearts continue to function adequately. Most children will also need heart medication(s). Complications going forward can include arrhythmias (abnormal heart rhythms), heart failure, blood clots, and a few other rare problems.

Your cardiologist will help you create a long-term care program as your baby grows into childhood and his teen years. Families with a child with HLHS will have an ongoing relationship with their cardiologist. We will treat your child if complications arise, and we’ll advise on daily-life issues such as exercise, activity levels, nutrition and pregnancy precautions.
 

Where can my child find care and support when he grows up?

• Our Boston Adult Congenital Heart and Pulmonary Hypertension Service (BACH) provides long-term inpatient and outpatient care and advanced therapeutic options for patients with congenital heart disease and pulmonary hypertension as they progress into adulthood.

BACH is an international center for excellence, with physicians and services from Children’s, Brigham and Women’s Hospital and Beth Israel Deaconess Medical Center. The center promotes and supports clinical and scientific research for the advancement of care of these patients, and is a leader in the education of providers caring for this unique population.

• The Adult Congenital Heart Association (ACHA) is a national not-for-profit organization dedicated to improving and extending the life of adults with congenital heart defects, now thought to number at least one million. The organization serves and supports many such adults, their families and the medical community, as well as conducting research and providing advocacy, outreach and education.
   

What causes HLHS?

It’s important for parents to understand that you’ve done nothing to cause HLHS and its accompanying defects. Nothing you have ingested or have been exposed to environmentally has been definitively linked to having a child with HLHS.

HLHS is the result of the underdevelopment of sections of the fetal heart during the first eight weeks of pregnancy. Congenital heart defects usually occur sporadically (by chance), with no clear reason for their development. Familial cases have been reported, but the genetic link has yet to be clarified.

FAQ
 

Q: What is hypoplastic left heart syndrome (HLHS)?

A: In the congenital heart defect HLHS, most of the structures on the left side of the heart are too small and underdeveloped (hypoplastic) to provide enough red blood flow for the body’s needs. The small left ventricle, which needs to be strong in order to pump blood out to the body, simply can’t function effectively. Other left heart structures can also be underdeveloped in varying degrees—including the mitral valve, aortic valve and aorta.

Q: How common is hypoplastic left heart syndrome (HLHS)?

A: A rare and complex heart defect, HLHS occurs in about four out of every 10,000 live births and represents 8 percent of all cases of congenital heart disease. It occurs slightly more often in boys than girls.

Q: Will my baby need a heart transplant?

A: A very few institutions perform heart transplants—rather than the staged Fontan reconstructive surgeries—as a primary therapy. At Children’s, we perform transplants only if patients don’t respond to other surgery. Such an occurrence at Children’s is very unusual.

Q: If my child has HLHS, will he be OK?

A: Open-heart surgery at Children’s has one of the highest success rates in the United States among large pediatric cardiac centers. However, your child will need additional staged surgeries in his first few years of life, and will need continued cardiac care throughout his life.

Q: What treatment does Children’s perform that other centers do not?

A: Children’s physicians have refined fetal cardiac intervention, in which catheterization techniques are used to open the baby’s blocked heart valves or foramen ovale in utero. Children’s is the world’s largest and most experienced center successfully performing fetal cardiac interventions. Patient families from all over the world seek us out for this advanced capability.

Q: How does Children’s treat newborns with HLHS?

A: We treat HLHS with a series of three palliative surgeries performed in the baby’s first few years. The goals of the surgeries are to:

• enable the fully-functioning right ventricle to do the work normally done by two ventricles
• separate the blue, or low-oxygen-content blood (pulmonary circulation), from the red, or well-oxygenated blood (systemic circulation)

For details, see Treatment & care.

Q: What are the symptoms of HLHS?

A: At first, a newborn with HLHS may appear normal. But symptoms usually develop in the first few hours or days of life. Lack of vital blood flow causes the baby to go into profound shock, endangering the brain, liver, kidneys and other vital organs. Symptoms may include:

• rapid breathing or shortness of breath
• rapid heartbeat or pounding heart
• poor suckling and feeding
• cold extremities (poor perfusion)
• blue color of the skin, lips and nailbeds (cyanosis)
• lethargy
   

Q: If my child has HLHS, what should I ask my doctor?

A: If your child is diagnosed with hypoplastic left heart syndrome, you may feel overwhelmed with information. It can be easy to lose track of the questions that occur to you. Lots of parents find it helpful to jot down questions as they arise—that way, when you talk to your child’s doctors, you can be sure that all of your concerns are addressed.

Some of the questions you may want to ask include:

• What is happening to my child, and why?
• What further tests will you perform to diagnose my child?
• What actions might you take after you reach a diagnosis?
• Are there alternative therapies?
• Will there be restrictions on my child’s activities?
• Will there be long-term effects?
• What can we do at home?
   

Q: When is HLHS usually diagnosed, and how?

A: Most pregnant women have fetal ultrasounds in the course of their pregnancies. If a basic (level one) ultrasound shows the potential for heart abnormalities, a more detailed cardiac ultrasound (fetal echocardiogram) can correctly diagnose your baby’s heart defect. In addition, an advanced general (level two) ultrasound at Children’s Advanced Fetal Care Center (AFCC) can detect some other anomalies, if these are present.

Q: What benefit is there to a prenatal (fetal) ultrasound that detects HLHS while the baby is still in the womb?

A: Being able to diagnose HLHS through prenatal cardiac ultrasound gives doctors a head-start in determining next steps. In a few select situations, a fetus with HLHS can be a candidate for fetal therapy. At Children’s Hospital Boston and Brigham and Women’s Hospital, we can do a fetal cardiac intervention, in which doctors perform procedures on the baby’s heart while still in the womb.

If your baby is not a candidate for fetal intervention, we can plan in advance for his effective delivery, and for his immediate stabilization once he’s born. Upon the baby’s birth, our AFCC team will bring together all the pediatric and obstetric specialists necessary for critical care, as well as support services for families.

Q: What questions about my baby’s heart should I ask my doctor or technician when I’m having an ultrasound?

A: Ask your doctor or technician:

• Is the baby’s heart normal, and if not why not?
• Do you see four chambers in the baby’s heart?
  • Are there two upper chambers (left and right atria) with valves controlling blood flow into the heart?
  • Are there two lower chambers (left and right ventricles) with valves controlling blood flow out to the body (aortic) and lungs (pulmonary)?
• Do the two valves and vessels exit the heart in a crossing fashion, with one going from right to left (aortic), and the other going from left to right (pulmonary)?
  
   

Q: What should we do at home after HLHS surgeries?

A: Consult your child’s cardiologist for guidance on specific steps for follow-up care at home. And as your baby recovers and grows, be sure to follow a regular program of well-baby/well-child checkups.

Q: What is the long-term outlook for HLHS-affected children?

A: Treatment for HLHS has been in existence only since the 1980s, and the earliest surgeries were relatively unsuccessful. The oldest HLHS survivors are now only in their 20s.

Children’s cardiologists will follow your child’s recovery and progress, and will provide further treatment, if needed. There is the risk of complications, especially arrhythmias and heart failure. And the potential does exist for needing a heart transplant in early or mid-adulthood.

Q: What causes HLHS?

A: It’s important to understand that as parents, you’ve done nothing to cause HLHS and its associated defects. Nothing you have ingested or have been exposed to environmentally has been linked to having a child with HLHS. Familial cases have been reported, but the genetic link has yet to be clarified.

HLHS is the result of underdevelopment of sections of the fetal heart during the first eight weeks of pregnancy. But it’s not understood why the heart doesn’t develop normally. Congenital heart defects usually occur sporadically (by chance), with no clear reason for their development.

Q: What is Children’s experience treating congenital heart defects?

A: Children’s surgeons treat some of the most complex pediatric heart conditions in the world, with top success rates. Our experts have pioneered some of medical science’s most advanced heart treatments, now in use around the globe. Children’s is the world’s largest and most experienced program for fetal heart intervention.

Q: What heart research and innovations are coming from Children’s?

A: Children’s is a world pioneer in the development and use of innovative fetal intervention to treat hypoplastic left heart syndrome. Thanks to Children’s research and refinements of technique, our Advanced Fetal Care Center offers the world’s largest and most experienced program for fetal heart intervention for HLHS.

Causes
 

It’s important to understand that as parents, you’ve done nothing to cause HLHS and its associated defects. Nothing you have ingested or have been exposed to environmentally has been linked to having a child with HLHS. Familial cases have been reported, but the genetic link has yet to be clarified.

HLHS is the result of underdevelopment of sections of the fetal heart during the first eight weeks of pregnancy. But it’s not understood why some babies’ hearts don’t develop normally. Congenital heart defects usually occur sporadically (by chance), with no clear reason for their development.

Symptoms
 

At first, a newborn with HLHS may appear normal. But symptoms usually develop in the first few hours or days of life. Lack of vital blood flow causes the baby to go into profound shock, endangering the brain, liver, kidneys and other vital organs. Symptoms may include:

• rapid breathing or shortness of breath
• rapid heartbeat or pounding heart
• poor suckling and feeding
• cold extremities (poor perfusion)
• blue color of the skin, lips and nailbeds (cyanosis)
• lethargy
  
   

When to seek medical advice
 

Call your health care provider immediately if your baby or child is having difficulty breathing or is breathing rapidly, has a bluish color, tires easily, has cold hands and feet, is drowsy or unresponsive and is uninterested in eating.

Questions to ask your doctor
 

After your child is diagnosed with HLHS, you may feel overwhelmed with information. It can be easy to lose track of the questions that occur to you. Lots of parents find it helpful to jot down questions as they arise—that way, when you talk to your child’s doctors, you can be sure that all of your concerns are addressed.

Some of the questions you may want to ask include:

• What is happening to my child, and why?
• What further tests will you perform to diagnose my child?
• What actions might you take after you reach a diagnosis?
• Are there alternative therapies?
• Will there be restrictions on my child’s activities?
• Will there be long-term effects?
• What can we do at home?
  
   

Who’s at risk
 

Congenital heart defects usually occur sporadically (by chance), with no clear reason for their development. So, it’s difficult to predict who’s at risk. Familial cases have been reported, but the genetic link has yet to be clarified.

Complications

Children who have had HLHS reconstruction surgeries can be susceptible to arrhythmias, heart failure and blood clots as they go forward. And the potential does exist for needing a heart transplant in early or mid-childhood.

Long-term outlook
 

In many cases, the Fontan reconstructive surgeries now can palliate (not cure) HLHS, so the outlook for your child is positive. Children who have undergone HLHS reconstruction can be susceptible to arrhythmias, heart failure, blood clots and a few other complications. And the potential does exist for needing a heart transplant in early or mid-childhood.

Your cardiologist will help create a long-term care plan as your baby grows into childhood and his teen years. Most people who have had congenital heart disease repair have an ongoing relationship with their cardiologist; we will consult and treat your child if complications arise, and we’ll advise on daily-life issues such as exercise, activity levels, nutrition and pregnancy precautions.

For teens
 

As a teen with a congenital heart defect, you have a lot to cope with. Besides the typical issues any teenager faces—from social acceptance to body changes and more—you also have to deal with medical appointments and procedures, some delay of your natural wish for independence, the consciousness of feeling different and personal responsibility for maintaining your good health.

If you as a teen (or as the parent of a teen) feel overwhelmed, depressed or anxious through this time, speak to your doctor to get help.

What you can do at home
 

Consult your child’s cardiologist for guidance on specific steps for follow-up care at home. And as your baby recovers and grows, be sure to follow a regular program of well-baby/well-child checkups.

Prevention
 

It’s important to understand that as parents, you’ve done nothing to cause HLHS and its accompanying defects, and there are no precautions you could have taken to prevent it. Congenital heart defects usually occur sporadically (by chance), with no clear reason for their development.

HLHS Glossary
 

• Advanced Fetal Care Center (AFCC) at Children’s: the only comprehensive fetal care center in New England, and one of just a few in the United States. The AFCC is the first and most experienced center performing fetal cardiac interventions—treating abnormalities such as HLHS in utero to reduce potentially fatal concerns after delivery.
   
• aorta: one of the heart’s two great arteries. In a normal heart, the aorta arises from the left ventricle and pumps oxygen-rich blood out to the body. In HLHS, the aorta can be too undersized to function adequately.
   
• cardiac catheterization: provides detailed visual information and measurements about the structures inside the heart, cardiac catheterization is a procedure that can be performed on a fetus, a baby, a child or an adult. Catheterization can be diagnostic-only, diagnostic and therapeutic, or diagnostic and interventional.
   
• cardiac/cardio-: pertaining to the heart
   
• cardiac intervention: a minimally invasive procedure, such as cardiac catheterization or angioplasty, to diagnose and treat heart disease
   
• cardiac magnetic resonance imaging (MRI): a non-invasive diagnostic tool using 3-D imaging technology produced by magnets to accurately determine the blood flow and functioning of your child's heart
   
• cardiac surgery: surgical procedure performed on the heart
   
• cardiac surgeon: doctor who performs surgery on the heart. A pediatric cardiac surgeon performs surgery on the hearts of infants and children.
   
• cardiologist: doctor who diagnoses and treats heart problems non-surgically. A pediatric cardiologist treats infants and children with heart problems.
   
• The Center for Families at Children’s: dedicated to helping families find the information, services and resources they need to understand their child’s medical condition and take part in their care
   
• cyanosis (cyanotic): blue color of skin, lips and nailbeds caused by lack of oxygen-rich (red) blood circulating in baby’s bloodstream—a major symptom of HLHS
   
• congenital heart defect: heart defect present at birth. The heart usually forms in the first eight weeks of fetal development. It's thought that most congenital heart defects develop during this period.
   
• diagnosis: medical determination of illness or disease based on physical examinations and advanced technology diagnostic testing tools
   
• echocardiogram (echo, cardiac ultrasound): a diagnostic tool that evaluates the structure and function of the heart using electronically recorded sound waves that produce a moving picture of your child’s heart and heart valves. The ultrasound can detect an HLHS defect.
   
• electrocardiogram (ECG, EKG): a diagnostic tool that evaluates the electrical activity of your child’s heart. An EKG is usually the initial test for evaluating the causes of symptoms and detecting heart abnormalities, including HLHS.
   
• fetal cardiac intervention: Advanced catheterization treatment of the baby’s heart while still in utero.
   
• fetal echocardiogram (fetal ultrasound): a diagnostic tool that uses sound waves to evaluate the structure and function of the baby’s heart while still in utero. The ultrasound can detect an HLHS defect in the fetus.
   
• fetal magnetic imaging (MRI): a non-invasive diagnostic tool that uses 3-D imaging technology produced by magnets to accurately determine the blood flow and functioning of your child’s heart in utero. Drawing on our expertise in pediatric imaging, Children’s is setting a new standard in fetal MRI.
   
• Fontan sequence: a series of three palliative operations performed on children whose congenital heart defect results in just one full-sized functioning ventricle (single ventricle defect), including HLHS.  They are the Norwood (and its alternatives), the bi-directional-Glenn Shunt and the Fontan Operation. The Fontan surgeries are usually performed at intervals starting at a few months and ending at a few years of age.
   
• heart valves: valves (tricuspid, pulmonary, mitral and aortic) that regulate uni-directional blood flow into and out of the heart chambers. In HLHS, the mitral and aortic valves are undersized.
   
• hypoplastic left heart syndrome (HLHS): a congenital (present at birth) heart defect in which most of the structures on the left side of the heart—and especially the left ventricle—are too small and underdeveloped to provide enough red blood flow for the body’s needs
   
• interventional cardiologist: a doctor who specializes in performing minimally invasive procedures, such as cardiac catheterization or angioplasty, to diagnose and treat heart disease
   
• symptoms: the presenting reasons why a child needs medical attention. A symptom’s characteristics—including but not limited to onset, quality, triggers and severity—help diagnosticians to determine an illness or disease, or to determine what further testing is needed to determine the illness or disease.
   
• palliative: aiming to reduce the severity and impact of a disease, rather than cure it
   
• patent ductus arteriosus (PDA): a blood vessel (the ductus arteriosus) that connects the two great arteries (the aorta and the pulmonary artery) and usually closes soon after birth. As long as the PDA remains open (patent), blood can pass from the right ventricle and pulmonary artery to the aorta and body, allowing some oxygen-rich blood to circulate.
   
• patent foramen ovale (PFO): The foramen ovale is a small opening between the right and left atria, normally present in utero, but which usually closes shortly after birth. With HLHS, it’s important that the foramen ovale stay open (patent), as this allows blood returning from the lungs to cross from the left atrium to the right atrium and out to the body via the right ventricle and pulmonary artery.
   
• pulmonary artery: one of the heart’s two great arteries. In a normal heart, the pulmonary artery arises from the right ventricle and carries oxygen-poor blood to the lungs, where it receives oxygen.
   
• pulmonary artery banding: a repair in which a band is secured around the pulmonary artery to limit blood flow to the lungs. Pulmonary banding is an aspect of the hybrid procedure, one of the surgical options for treating HLHS.
   
• shunt: an artificial connection of blood vessels in order to redirect blood or other fluids. In pediatric cardiology and cardiac surgery, this usually refers to a Gore-Tex (a synthetic material) tube connected between the aorta or one of its branches and the pulmonary artery.
   
• single ventricle defect (SVD): one of several congenital (present at birth) heart defects in which the heart has only one fully functioning ventricle. Hypoplastic left heart syndrome (HLHS) is a single ventricle defect.
   
• sporadic: occurring by chance, occasionally, not inherited

For a more complete list of cardiovascular terms, visit our Cardiovascular glossary.

For in-depth visual information on several of the conditions, diagnostic tools and procedures described above, visit our Multimedia library.