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Disease Profile

Hypoplastic left heart syndrome

Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.


US Estimated

Europe Estimated

Age of onset





Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.


Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.


dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.


recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.


Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.


Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.


Not applicable


Other names (AKA)



Congenital and Genetic Diseases; Heart Diseases


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]


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

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.

Medical Terms Other Names
Learn More:
80%-99% of people have these symptoms
Hypoplastic left heart
Underdeveloped left heart
30%-79% of people have these symptoms
Hypoplastic aortic arch
Underdeveloped aortic arch
5%-29% of people have these symptoms
Abnormality of chromosome segregation
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 ]

Maternal diabetes
gestational diabetes
Mitral atresia
Mitral stenosis
Patent ductus arteriosus
1%-4% of people have these symptoms
Aortic valve stenosis
Narrowing of aortic valve
Coarctation of aorta
Narrowing of aorta
Narrowing of the aorta

[ more ]

Percent of people who have these symptoms is not available through HPO
Aortic valve atresia
Autosomal dominant inheritance
Autosomal recessive inheritance
Oligogenic inheritance
Ventricular septal defect
Hole in heart wall separating two lower heart chambers


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]


    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 Providing General Support

      Learn more

      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.


          1. Single Ventricle Defects. American Heart Association. October 21, 2015; https://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; https://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; https://www.nlm.nih.gov/medlineplus/ency/article/001106.htm.
          7. Patnana SR. Pediatric Hypoplastic Left Heart Syndrome. Medscape Reference. December 30, 2015; https://emedicine.medscape.com/article/890196-overview.

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