Hypoplastic left heart syndrome

Disease Description (Causes and Symptoms)

• Definition and pathophysiology: The left ventricle, mitral and aortic valves, and ascending aorta are congenitally severely underdeveloped (left-sided hypoplasia), leaving the left heart unable to provide systemic blood flow. After birth, the right ventricle and ductus arteriosus (PDA) temporarily provide systemic outflow instead; when the PDA closes, severe systemic hypoperfusion (shock) and hypoxemia occur rapidly.
• Causes: The cause is unknown in most cases, but possible genetic predisposition, chromosomal abnormalities (which may be associated with conditions such as Down syndrome), rubella infection during pregnancy, and fetal exposure to medications (excessive alcohol, antiepileptic drugs, etc.) have been reported as risk factors.
• Main symptoms: Cyanosis appearing within several hours to several days after birth, rapid breathing (tachypnea), feeding difficulty, vomiting and poor weight gain, decreased urine output, pallor, cold extremities, hypotension and shock, and lethargy (floppiness). Symptoms may be delayed initially because the ductus arteriosus remains open.
• Epidemiology (summary): Occurs in approximately 0.05–0.25 per 1,000 live births in Western countries and accounts for approximately 1–3% of all congenital heart disease. More common in boys (approximately 67%). If untreated, the risk of death during the neonatal period is very high (for example, many deaths occur within the first month of life).

Treatment Methods (Standard Treatment, Medications·Procedures·Surgery, Lifestyle Management and Precautions)

• Emergency and initial treatment
  • Intravenous prostaglandin E1 (PGE1) to maintain the ductus arteriosus and secure systemic blood flow.
  • If necessary, conservative treatment such as mechanical ventilation (oxygen and ventilatory support), fluids, vasodilators, inotropes (to support inability to relax and low cardiac output), and diuretics.
  • If interatrial communication is restricted, balloon atrial septostomy to secure a passage between the right and left atria.
  • Active management of systemic status (body temperature, blood glucose, electrolytes, and hemoglobin).
• Staged repair (standard approach)
  1. First-stage surgery — Norwood procedure (neonatal period): Reconstruction of the ascending aorta and securing pulmonary blood flow (such as with a Blalock–Taussig shunt). (Example of reported operative mortality: approximately 35%)
  2. Second-stage surgery — Bidirectional Glenn connection (bidirectional superior vena cava–pulmonary artery connection), usually after 4–6 months of age (low operative mortality, reported as ≤5%).
  3. Third-stage surgery — Fontan procedure (around 2–4 years of age): Connecting inferior vena cava blood flow to the pulmonary circulation to complete the single-ventricle circulation.
  • The proportion of patients who successfully complete all staged surgeries varies by institution, but some centers have reported 5-year survival rates of up to approximately 70%. The proportion able to progress from the Norwood procedure to the Fontan procedure varies by study and center and has been reported at approximately 50% in some samples.
• Alternative and adjunctive treatments
  • Some patients may choose heart transplantation from the initial stage (depending on the institution and the patient’s condition).
  • Long-term medication: Heart failure medications before and after surgery and after the Fontan procedure, consideration of anticoagulants and antithrombotic agents (individualized), and antiarrhythmic medications when necessary.
• Long-term follow-up and complication management (precautions)
  • Lifelong follow-up with a pediatric and adult congenital heart disease specialist is necessary (complications may occur during adulthood).
  • Complications in Fontan patients: Arrhythmias, protein-losing enteropathy, hepatic fibrosis/liver dysfunction, venous thrombosis/pulmonary embolism, heart failure, and reduced exercise tolerance.
  • The risk of systemic hypoperfusion increases with infection (especially after procedures or surgery) and dehydration — immediate medical attention is recommended in cases of infection or dehydration.
  • PGE1 administration may cause respiratory depression (apnea), requiring close monitoring.
  • Vaccination is recommended (especially to prevent severe infections such as respiratory syncytial virus); follow the treating physician’s instructions regarding antibiotics before and after surgery and prevention of infective endocarditis.
  • Genetic counseling is recommended (regarding family history and future pregnancy plans).

Checklist Before an Outpatient Visit (Examples of Documents to Bring, Tests, and Symptom Records)

• Items to bring
  • List of currently used medications (including doses and administration times) and information about medication allergies.
  • Copies of records of previous surgeries and procedures (name and date of surgery) and hospitalizations, as well as recent echocardiography (echo), electrocardiography (ECG), and cardiac catheterization (cath) results.
  • Recent growth measurements (weight and height), oxygen saturation readings (if available, measurements from the right and left limbs), and records of daily activity and feeding patterns.
  • Records of recent fever, respiratory symptoms, vomiting or diarrhea, and changes in urine output.
• Questions for symptom monitoring (for taking notes)
  • Whether pallor or cyanosis is better or worse than usual; increased feeding time or weight loss; lethargy or sleepiness during the day; worsening shortness of breath or rapid breathing; and decreased urine output (compared with the usual daily baseline).
  • Whether any recent medication doses were missed (especially intravenous medications such as PGE1, which require inpatient treatment).
• Preparation for the day of the outpatient visit
  • A recent photo of the child (for observing cyanosis) or brief notes made when symptoms occurred (when, how often, etc.).

Examples of General Questions to Ask the Doctor

• What treatment (surgery, timing of surgery, and strategy) do you recommend now for this condition? What are the advantages and disadvantages?
• What are the expected complications and mortality rates for each surgery stage? What is our child’s individual risk?
• What are the side effects of the medications currently being given, such as PGE1, and what signs should be monitored?
• What are the expected long-term lifestyle limitations and exercise guidelines, and what is the outlook for adulthood (cardiac output, pregnancy, etc.)?
• Are genetic testing or family counseling needed? What is the risk of recurrence in future siblings?

Examples of Condition-Specific Questions

• Is the passage between our child’s atria (atrial septum) restricted? Is balloon atrial septostomy needed, and when would it be performed?
• Is there a reason to recommend early heart transplantation instead of the Norwood procedure? Could our child be a candidate for transplantation (opportunity, criteria, waiting time, etc.)?

(If necessary, printing or taking notes on the questions above and showing them directly during the consultation may make the discussion smoother.)