National Center for Advancing and Translational Sciences Genetic and Rare Diseases Information Center, a program of the National Center for Advancing and Translational Sciences

Hypoplastic left heart syndrome

Hypoplastic left heart syndrome (HLHS) is a heart condition present from birth (congenital heart defect). In HLHS, the heart's left side (including the aorta, aortic valve, left ventricle and mitral valve) is underdeveloped.[1] At birth, oxygen-rich blood bypasses the underdeveloped left side of the heart, going through openings between the left and right side that normally close a few days after birth (the patent ductus arteriosus and the patent foramen ovale). The right side of the heart then pumps blood to the lungs and the body. Therefore, there may be no symptoms for a few days. However, when these openings close, oxygen-rich blood cannot easily get to the rest of the body. Symptoms then develop quickly, and may include problems breathing, pounding heart, weak pulse, and/or an ashen or bluish skin color. Some children with HLHS also have other heart defects, such as an atrial septal defect.[2]

In most children with HLHS, the cause is not known.[2] It typically occurs sporadically in otherwise normal babies.[3] In some children, isolated HLHS is known to be genetic. These cases may be due to mutations in the GJA1 gene with autosomal recessive inheritance, or the NKX2-5 gene with autosomal dominant inheritance.[4][5] HLHS has also been reported with certain genetic disorders including Turner syndrome, Jacobsen syndrome, trisomy 13, and trisomy 18.[3]

If not treated, HLHS is fatal within the first few days or weeks of life.[1] While treatment is difficult, surgical and medical interventions have improved chances of survival. Treatment may include a series of surgeries to restore function to the left side of the heart (staged reconstruction), or heart transplant. However, even with treatment, lifelong complications are possible and life expectancy may be reduced.[3]
Last updated: 6/5/2018
A newborn with HLHS may not have any symptoms immediately after birth. Signs and symptoms usually develop within a few hours or days of birth. These symptoms may include:[6][2][7]
  • Cyanosis (bluish discoloration of skin or appearing "ashen")
  • Cold hands and feet
  • Lack of energy (lethargy)
  • Low output of urine
  • Weak pulse
  • Poor suckling and feeding
  • Pounding heart
  • Problems breathing (rapid breathing or shortness of breath)
  • Metabolic acidosis
Last updated: 9/7/2017

This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Showing of 15 |
Medical Terms Other Names
Learn More:
HPO ID
80%-99% of people have these symptoms
Hypoplastic left heart
Underdeveloped left heart
0004383
30%-79% of people have these symptoms
Hypoplastic aortic arch
Underdeveloped aortic arch
0012304
5%-29% of people have these symptoms
Abnormality of chromosome segregation 0002916
Atrial septal defect
An opening in the wall separating the top two chambers of the heart
Hole in heart wall separating two upper heart chambers
[ more ] 		0001631
Maternal diabetes
gestational diabetes
0009800
Mitral atresia 0011560
Mitral stenosis 0001718
Patent ductus arteriosus 0001643
1%-4% of people have these symptoms
Aortic valve stenosis
Narrowing of aortic valve
0001650
Coarctation of aorta
Narrowing of aorta
Narrowing of the aorta
[ more ] 		0001680
Percent of people who have these symptoms is not available through HPO
Aortic valve atresia 0010883
Autosomal dominant inheritance 0000006
Autosomal recessive inheritance 0000007
Oligogenic inheritance 0010983
Ventricular septal defect
Hole in heart wall separating two lower heart chambers
0001629
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Last updated: 7/1/2020
HLHS typically occurs sporadically (randomly), in otherwise normal babies with no family history of HLHS.[3] In a few children, isolated HLHS is known to be genetic. These cases may be due to mutations in the GJA1 gene with autosomal recessive inheritance, or the NKX2-5 gene with autosomal dominant inheritance.[4][5]

Most congenital heart defects are thought to be caused by interactions between unidentified genes and the environment. This is called multifactorial inheritance. When the specific cause of isolated HLHS in a child is not known, the recurrence risk of left heart disease in first degree relatives of infants with HLHS is estimated at 2 to 4 percent.[3]

HLHS has also been reported with certain genetic disorders including Turner syndrome, Jacobsen syndrome, trisomy 13, and trisomy 18.[3]
Last updated: 9/8/2017

Making a diagnosis for a genetic or rare disease can often be challenging. Healthcare professionals typically look at a person’s medical history, symptoms, physical exam, and laboratory test results in order to make a diagnosis. The following resources provide information relating to diagnosis and testing for this condition. If you have questions about getting a diagnosis, you should contact a healthcare professional.

Testing Resources

  • The Genetic Testing Registry (GTR) provides information about the genetic tests for this condition. The intended audience for the GTR is health care providers and researchers. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.
    Hypoplastic left heart syndrome 1
    Hypoplastic left heart syndrome 2
Once the diagnosis of HLHS is made, the baby will likely be admitted to the neonatal intensive care unit (NICU).[6] Management options should be clearly explained to parents and families to allow them to make the best possible informed decision. Choices for management may include staged surgeries, heart transplantation, and comfort care measures (with no surgical interventions). Most pediatric cardiologists and surgeons in the US recommend staged surgery, and there is debate among experts about whether comfort care should be offered as an option at all. Improvements in medical and surgical care have improved outcomes for children with HLHS significantly.[3] However, babies that are treated with surgery are not guaranteed to survive. While some doctors consider heart transplantation an alternative to the 3 step surgery, there are few donated hearts available for small infants.[6]

Initial management focuses on helping the baby breathe and keeping the ductus arteriosis open so blood circulates through the body (with prostaglandin E1). These measures stabilize the baby until the first surgery is performed.[6][3]

Staged surgery consists of 3 procedures: one in the neonate, one at 3 to 6 months of age, and one at 18 to 30 months of age.[3] The choice of the specific procedure for each stage may vary depending on the baby's individual circumstances. Some people may need more surgeries later on if they develop complications from the condition or from prior surgeries.[6]

Last updated: 9/8/2017
If left untreated, HLHS is fatal. Survival rates for the staged surgical repair continue to rise as surgery techniques and care after surgery improve.[6] There are currently estimates of three- to five-year survival rates of 70% for infants who have the stage I repair. For children who survive to the age of 12 months, long-term survival is about 90 percent.[3] The size and function of the right ventricle are important in determining the child's outcome after surgery.[6]

There is little data on the quality of life for patients with HLHS. With more people surviving the staged surgeries, more information is now being gathered about the long-term experiences of people born with HLHS.[3] There is significant morbidity for those who survive treatment for HLHS, including an increased risk of thrombotic (blood clotting) complications, decrease in exercise tolerance, and neurodevelopmental impairment. Thrombotic complications may be associated with mortality, stroke, and pulmonary embolism.[3]
Last updated: 6/5/2018
The Centers for Disease Control and Prevention (CDC) has estimated that each year about 960 babies in the United States are born with hypoplastic left heart syndrome (about 1 in every 4,344 babies).[2] HLHS accounts for 2 to 3 percent of all congenital heart disease. The number of cases may be underestimated due to the unknown rate of miscarriages or elective pregnancy terminations of unborn babies with HLHS.[3]
Last updated: 9/7/2017

If you need medical advice, you can look for doctors or other healthcare professionals who have experience with this disease. You may find these specialists through advocacy organizations, clinical trials, or articles published in medical journals. You may also want to contact a university or tertiary medical center in your area, because these centers tend to see more complex cases and have the latest technology and treatments.

If you can’t find a specialist in your local area, try contacting national or international specialists. They may be able to refer you to someone they know through conferences or research efforts. Some specialists may be willing to consult with you or your local doctors over the phone or by email if you can't travel to them for care.

You can find more tips in our guide, How to Find a Disease Specialist. We also encourage you to explore the rest of this page to find resources that can help you find specialists.

Healthcare Resources

Related diseases are conditions that have similar signs and symptoms. A health care provider may consider these conditions in the table below when making a diagnosis. Please note that the table may not include all the possible conditions related to this disease.

Conditions with similar signs and symptoms from Orphanet
Differential diagnosis includes other left-sided obstructive lesions where the systemic circulation is dependent on ductal flow (critical aortic stenosis, coarctation of the aorta, interrupted aortic arch).
Visit the Orphanet disease page for more information.

Research helps us better understand diseases and can lead to advances in diagnosis and treatment. This section provides resources to help you learn about medical research and ways to get involved.

Clinical Research Resources

  • ClinicalTrials.gov lists trials that are related to Hypoplastic left heart syndrome. Click on the link to go to ClinicalTrials.gov to read descriptions of these studies.

    Please note: Studies listed on the ClinicalTrials.gov website are listed for informational purposes only; being listed does not reflect an endorsement by GARD or the NIH. We strongly recommend that you talk with a trusted healthcare provider before choosing to participate in any clinical study.

Patient Registry

  • A registry supports research by collecting of information about patients that share something in common, such as being diagnosed with Hypoplastic left heart syndrome. The type of data collected can vary from registry to registry and is based on the goals and purpose of that registry. Some registries collect contact information while others collect more detailed medical information. Learn more about registries.

    Registries for Hypoplastic left heart syndrome:
    CHD GENES Study
     

Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

Organizations Supporting this Disease

Living with a genetic or rare disease can impact the daily lives of patients and families. These resources can help families navigate various aspects of living with a rare disease.

Financial Resources

These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

Where to Start

  • The American Heart Association has an information page on Hypoplastic left heart syndrome. The American Heart Association is the nation’s oldest and largest voluntary organization dedicated to fighting heart disease and stroke.
  • You can obtain information on this topic from the Centers for Disease Control and Prevention (CDC). The CDC is recognized as the lead federal agency for developing and applying disease prevention and control, environmental health, and health promotion and education activities designed to improve the health of the people of the United States.
  • The Children's Hospital of Philadelphia offers information on Hypoplastic left heart syndrome.
  • The Mayo Clinic provides information about Hypoplastic left heart syndrome. Click on the above link to access this information.
  • MedlinePlus was designed by the National Library of Medicine to help you research your health questions, and it provides more information about this topic.
  • The Merck Manual provides information on this condition for patients and caregivers. 
  • The National Organization for Rare Disorders (NORD) has a report for patients and families about this condition. NORD is a patient advocacy organization for individuals with rare diseases and the organizations that serve them.
  • The The Cleveland Clinic Web site has an information page on Hypoplastic left heart syndrome. Click on the Cleveland Clinic link to view this page.

In-Depth Information

  • Medscape Reference provides information on this topic. You may need to register to view the medical textbook, but registration is free.
  • The Merck Manual for health care professionals provides information on Hypoplastic left heart syndrome.
  • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
  • Online Mendelian Inheritance in Man (OMIM) is a catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
    Hypoplastic left heart syndrome 1 (HLHS1)
    Hypoplastic left heart syndrome 2 (HLHS2)
  • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
  • PubMed is a searchable database of medical literature and lists journal articles that discuss Hypoplastic left heart syndrome. Click on the link to view a sample search on this topic.

Questions sent to GARD may be posted here if the information could be helpful to others. We remove all identifying information when posting a question to protect your privacy. If you do not want your question posted, please let us know. Submit a new question

  • Years ago I lost an infant to HLHS. I have another child who is now an adult. Should he be genetically tested and counseled before having children? See answer

  • My best friend's baby has hypoplastic left heart syndrome and she been told that it's not common here in Australia. The doctors don't know a lot about it and her baby has only days to live. How common is it? What is the prognosis? See answer


  1. Single Ventricle Defects. American Heart Association. October 21, 2015; http://www.heart.org/HEARTORG/Conditions/CongenitalHeartDefects/AboutCongenitalHeartDefects/Single-Ventricle-Defects_UCM_307037_Article.jsp#.WbFnnbKGND9.
  2. Facts about Hypoplastic Left Heart Syndrome. Centers for Disease Control and Prevention. November 8, 2016; http://www.cdc.gov/ncbddd/heartdefects/hlhs.html.
  3. Marshall A. Hypoplastic left heart syndrome. UpToDate. Waltham, MA: UpToDate; August, 2017; https://stage0www.uptodate.com/contents/hypoplastic-left-heart-syndrome?source=search_result&search=Hypoplastic+left+heart+syndrome&selectedTitle=1~42.
  4. HYPOPLASTIC LEFT HEART SYNDROME 1; HLHS1. OMIM. August 1, 2017; https://www.omim.org/entry/241550?search=hypoplastic%20left%20heart&highlight=heart%20left%20hypoplastic.
  5. HYPOPLASTIC LEFT HEART SYNDROME 2; HLHS2. OMIM. January 17, 2012; https://www.omim.org/entry/614435?search=hypoplastic%20left%20heart&highlight=heart%20left%20hypoplastic.
  6. Weinrauch LA. Hypoplastic left heart syndrome. MedlinePlus. October 22, 2015; http://www.nlm.nih.gov/medlineplus/ency/article/001106.htm.
  7. Patnana SR. Pediatric Hypoplastic Left Heart Syndrome. Medscape Reference. December 30, 2015; http://emedicine.medscape.com/article/890196-overview.