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PubMed This is a summary of 17 peer-reviewed journal articles Updated
Pediatric Cardiology

Anatomy and Subtypes: Mapping Your Child's Heart

At a Glance

Hypoplastic Right Heart Syndrome (HRHS) is a congenital defect where the heart's right side is underdeveloped. The main subtypes, PA-IVS and Tricuspid Atresia, block blood flow to the lungs. Diagnosis occurs via fetal ultrasound or after birth when a baby develops a blue skin tint (cyanosis).

Understanding the anatomy of Hypoplastic Right Heart Syndrome (HRHS) requires looking at the right side of the heart as a specialized “pump system” that has failed to grow properly. In a healthy heart, the right ventricle receives oxygen-poor blood through the tricuspid valve and pumps it through the pulmonary valve to the lungs. In HRHS, one or more of these structures is too small, blocked, or missing, creating a “bottleneck” that prevents blood from reaching the lungs [1][2].

The Primary Subtypes of HRHS

Doctors generally group HRHS into two main categories based on which part of the “pump system” is most affected:

1. Pulmonary Atresia with Intact Ventricular Septum (PA-IVS)

In this subtype, the pulmonary valve (the exit door to the lungs) is completely sealed (atresia). Because the wall between the bottom chambers (ventricular septum) is solid (intact), the blood has no way to leave the right ventricle [1][3]. This creates high pressure inside the small right ventricle, which can stop it from growing or cause abnormal connections to form [1][4].

2. Tricuspid Atresia

In this subtype, the tricuspid valve (the entrance door to the right ventricle) never formed. Without this door, blood cannot enter the right ventricle at all [2]. As a result, the right ventricle remains very small and underdeveloped because it has nothing to pump [2][1].

A Critical Finding: RVDCC

One of the most important things your doctors will look for is Right Ventricle-Dependent Coronary Circulation (RVDCC).

Normally, the heart’s own muscle is fed by coronary arteries that branch off from the aorta (the body’s main pipeline). However, in some cases of HRHS—particularly PA-IVS—the high pressure in the small right ventricle forces the heart to create abnormal “shortcuts” called fistulae [4][5]. In RVDCC, the heart muscle becomes dependent on these shortcuts to get its blood supply [4][6].

Why this matters: If a surgeon were to suddenly lower the pressure in the right ventricle to “fix” it, the heart muscle could lose its blood supply, leading to a heart attack (ischemia) [4][7]. Identifying RVDCC early via echocardiogram or CT scan is vital because it often means a “two-ventricle repair” is too dangerous, and the child must follow a different surgical path [8][9].

How the Diagnosis is Made

The path to diagnosis depends heavily on when the defect is first spotted.

  • Fetal Diagnosis: Many cases are now caught during a mid-pregnancy “anatomy scan” (around 20 weeks). A fetal echocardiogram—a specialized ultrasound of the baby’s heart—can show that the right side looks smaller than the left or that blood is not moving through the valves correctly [10][11].
  • Postnatal Diagnosis: If not caught during pregnancy, a baby with HRHS will often appear healthy for the first few hours or days. However, once the ductus arteriosus (a natural fetal blood vessel) begins to close, the baby’s oxygen levels will drop, leading to cyanosis—a bluish tint to the skin, lips, or fingernails [12][13]. This is a medical emergency that requires immediate stabilization [12][3].

Differential Diagnosis: Is it HLHS?

Doctors must distinguish HRHS from other defects that look similar:

  • Hypoplastic Left Heart Syndrome (HLHS): This affects the left side of the heart. While both involve a small ventricle, they require different surgical approaches because the left ventricle is the one that normally pumps blood to the whole body [14][15].
  • Severe Pulmonary Stenosis: In this case, the pulmonary valve is very narrow but not completely blocked. These babies may have a better chance of their right ventricle growing after a procedure to open the valve [16][17].

By identifying the exact subtype and checking for RVDCC, your care team can build a precise roadmap for your child’s treatment [1][9].

Common questions in this guide

What are the main subtypes of Hypoplastic Right Heart Syndrome?
The two primary subtypes are Pulmonary Atresia with Intact Ventricular Septum (PA-IVS) and Tricuspid Atresia. Both conditions involve blockages in the heart valves that prevent the right ventricle from properly pumping blood to the lungs.
What is RVDCC and why is it an important finding?
RVDCC stands for Right Ventricle-Dependent Coronary Circulation, which means the heart muscle relies on abnormal pathways for its blood supply. Identifying this is critical because it changes the surgical plan to ensure the heart muscle continues getting enough oxygen.
How is Hypoplastic Right Heart Syndrome diagnosed before birth?
Many cases are detected during a routine mid-pregnancy anatomy scan around 20 weeks. A specialized ultrasound called a fetal echocardiogram can reveal if the right side of the heart is smaller than normal or if blood flow is restricted.
What are the symptoms of HRHS if it is not diagnosed prenatally?
If the condition is not detected during pregnancy, a baby may appear healthy for the first few days until a natural fetal blood vessel closes. At that point, oxygen levels drop rapidly, causing the baby's skin, lips, or nails to turn blue, which is a medical emergency.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Does my child have Pulmonary Atresia with Intact Ventricular Septum (PA-IVS), Tricuspid Atresia, or another subtype?
  2. 2.Has Right Ventricle-Dependent Coronary Circulation (RVDCC) been ruled out? If it is present, how does that change the surgical plan?
  3. 3.What is the Z-score of the tricuspid valve, and does the right ventricle have all three parts (inlet, apex, and outlet)?
  4. 4.Are there 'fistulae' or abnormal connections between the heart chambers and the coronary arteries?
  5. 5.Based on the current anatomy, are you aiming for a biventricular (two-pump) or single-ventricle (Fontan) pathway?

Questions For You

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References

References (17)
  1. 1

    Pulmonary Atresia With Intact Ventricular Septum With Borderline Tricuspid Valve: How Small Is Too Small.

    LaPar DJ, Bacha E

    Seminars in thoracic and cardiovascular surgery. Pediatric cardiac surgery annual 2019; (22()):27-31 doi:10.1053/j.pcsu.2019.02.007.

    PMID: 31027561
  2. 2

    Strain and Rotational Mechanics in Children With Single Left Ventricles After Fontan.

    Lopez C, Mertens L, Dragulescu A, et al.

    Journal of the American Society of Echocardiography : official publication of the American Society of Echocardiography 2018; (31(12)):1297-1306 doi:10.1016/j.echo.2018.09.004.

    PMID: 30344011
  3. 3

    Is there a transcatheter solution for a sick neonate with hypoplastic right heart syndrome?: Pulmonary valve perforation in a neonate with hypoplastic right ventricle with pulmonary atresia, restrictive VSD-a case report.

    Barwad P, Prasad K, Vijay J, Naganur S

    The Egyptian heart journal : (EHJ) : official bulletin of the Egyptian Society of Cardiology 2020; (72(1)):64 doi:10.1186/s43044-020-00097-7.

    PMID: 32990873
  4. 4

    Pulmonary atresia with intact ventricular septum: Intended strategies.

    Sukhavasi A, McHugh-Grant S, Glatz AC, et al.

    The Journal of thoracic and cardiovascular surgery 2022; (164(5)):1277-1288 doi:10.1016/j.jtcvs.2021.11.104.

    PMID: 35414413
  5. 5

    Aortopulmonary Window With Pulmonary Atresia and Interrupted Aortic Arch: A Very Rare Triad.

    Shahbah DA, Herrick NL, El-Said H, et al.

    World journal for pediatric & congenital heart surgery 2019; (10(6)):791-792 doi:10.1177/2150135119872199.

    PMID: 31701829
  6. 6

    Dor procedure for pulmonary atresia with intact ventricular septum in an infant.

    Kang Y, Kwak JG, Kim ER, Kim WH

    Interactive cardiovascular and thoracic surgery 2018; (26(2)):348-349 doi:10.1093/icvts/ivx285.

    PMID: 29049818
  7. 7

    Right Ventricle-Dependent Coronary Circulation: Location of Obstruction Is Associated With Survival.

    Spigel ZA, Qureshi AM, Morris SA, et al.

    The Annals of thoracic surgery 2020; (109(5)):1480-1487 doi:10.1016/j.athoracsur.2019.08.066.

    PMID: 31580859
  8. 8

    Computed Tomographic Angiography Provides Reliable Coronary Artery Evaluation in Infants With Pulmonary Atresia Intact Ventricular Septum.

    Malone LJ, Browne LP, Morgan GJ, et al.

    Seminars in thoracic and cardiovascular surgery 2024; (36(3)):336-344 doi:10.1053/j.semtcvs.2022.10.003.

    PMID: 36244628
  9. 9

    Perfusion Strategy to Prevent Right Ventricular Decompression on Cardiopulmonary Bypass During Extracardiac Fontan for Right Ventricle-Dependent Coronary Circulation.

    Joshi RK, Aggarwal N, Agarwal M, et al.

    World journal for pediatric & congenital heart surgery 2023; (14(4)):500-502 doi:10.1177/21501351231162894.

    PMID: 37006129
  10. 10

    Comparison of the Results of Prenatal and Postnatal Echocardiography and Postnatal Cardiac MRI in Children with a Congenital Heart Defect.

    Mamalis M, Koehler T, Bedei I, et al.

    Journal of clinical medicine 2023; (12(10)) doi:10.3390/jcm12103508.

    PMID: 37240614
  11. 11

    From Fetal Diagnosis to Staged Percutaneous Palliation: A Case of Double Right-Valve Dysplasia.

    Bonanni F, Cordisco A, Calabri GB, et al.

    JACC. Case reports 2025; (30(40)):105852 doi:10.1016/j.jaccas.2025.105852.

    PMID: 41165639
  12. 12

    [Application of arterial duct stent in ductus-dependent hypoplastic right heart syndrome].

    Luo G, Liu A, Wang KL, et al.

    Zhonghua er ke za zhi = Chinese journal of pediatrics 2020; (58(4)):319-323 doi:10.3760/cma.j.cn112140-20190907-00571.

    PMID: 32234140
  13. 13

    [Analysis of 15 cases of ductus arteriosus stent placement without a guiding catheter through femoral artery approach].

    Luo G, Pan SL, Ji ZX, et al.

    Zhonghua er ke za zhi = Chinese journal of pediatrics 2025; (63(3)):283-287 doi:10.3760/cma.j.cn112140-20241114-00830.

    PMID: 39979105
  14. 14

    Outcomes in Hypoplastic Left Heart Syndrome.

    Metcalf MK, Rychik J

    Pediatric clinics of North America 2020; (67(5)):945-962 doi:10.1016/j.pcl.2020.06.008.

    PMID: 32888691
  15. 15

    Common and divergent cellular aetiologies underlying hypoplastic left heart syndrome and hypoplastic right heart syndrome.

    Yu Y, Wang C, Ye S, et al.

    European heart journal 2025; (46(20)):1946-1949 doi:10.1093/eurheartj/ehaf121.

    PMID: 40048662
  16. 16

    Achieving biventricular circulation in patients with moderate hypoplastic right ventricle in pulmonary atresia intact ventricular septum after transcatheter pulmonary valve perforation.

    Chen RHS, K T Chau A, Chow PC, et al.

    Congenital heart disease 2018; (13(6)):884-891 doi:10.1111/chd.12658.

    PMID: 30238621
  17. 17

    [Fetal cardiac intervention and perioperative management of fetus with hypoplastic right heart syndrome].

    Luo G, Pan SL, Wang KL, et al.

    Zhonghua fu chan ke za zhi 2020; (55(12)):837-842 doi:10.3760/cma.j.cn112141-20200519-00425.

    PMID: 33355758

This page provides educational information about HRHS anatomy and subtypes. It is not medical advice and does not replace professional consultation. Always speak with your pediatric cardiologist regarding your child's specific diagnosis and surgical plan.

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