Transposition of the great arteries

Disease Description (Causes and Symptoms)

• Definition: Transposition of the great arteries (TGA) is a congenital heart defect in which the connections between the heart’s atria and ventricles are normal, but the connections between the ventricles and great arteries (aorta/pulmonary artery) are reversed. This means that the aorta arises from the right ventricle and the pulmonary artery arises from the left ventricle (ventriculoarterial discordance).
• Pathophysiology summary: The pulmonary and systemic circulations flow in parallel (“parallel circulation”): deoxygenated blood leaving the right side of the heart goes directly to the systemic circulation, while oxygenated blood leaving the left side returns to the lungs. Therefore, severe hypoxemia (which can be fatal) develops if there is no blood mixing. Survival consequently depends on the degree of blood mixing through an atrial septal defect (ASD)/patent foramen ovale (PFO), patent ductus arteriosus (PDA), or ventricular septal defect (VSD).
• Causes: The cause is unknown in most cases. An association with family history and genetic factors is possible. Infections such as rubella during pregnancy and exposure to medications such as antiepileptic drugs have been reported as risk factors.
• Main symptoms: Rapidly progressive cyanosis immediately after birth or during the neonatal period (marked central cyanosis), rapid breathing/dyspnea, tachycardia, feeding difficulties, lethargy, and metabolic acidosis (when mixing is inadequate)
• Clinical variant: When accompanied by a VSD, cyanosis may be mild, but heart failure and pulmonary hypertension may progress rapidly due to increased pulmonary blood flow.

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Treatment

• Emergency treatment (neonatal period)
  • Oxygen and supportive treatment: Maintain respiration and circulation. Mechanical ventilation if necessary.
  • Maintaining ductal patency: Administer prostaglandin E1 (PGE1) to open the PDA and increase blood mixing to maintain oxygen saturation — monitoring in a neonatal intensive care unit is required (side effects: hypotension, fever, apnea, etc.).
  • Percutaneous balloon atrial septostomy (Rashkind balloon atrial septostomy): When the opening between the atria is small or absent, this immediately increases blood mixing between the left and right atria and improves oxygen saturation. It is performed first when urgently indicated.
• Definitive (corrective) surgery
  • Arterial switch operation (Jatene): A complete corrective surgery that switches the aorta and pulmonary artery to their proper positions during the neonatal period and implants the coronary arteries into the neo-aorta; it is the standard treatment. Ideally, it is performed within 1–2 weeks after birth (it can also be performed up to 2 months after birth).
    • Important variable: Presence of coronary artery anomalies (abnormal findings in approximately 25–30%) — the difficulty of surgery and prognosis depend on the coronary artery anatomy.
  • Alternative surgery: If the coronary artery anatomy is unsuitable for an arterial switch or the condition is diagnosed late, other procedures such as an atrial switch operation (Mustard/Senning) may be considered.
  • Cases accompanied by a VSD: If the left ventricle is sufficiently thick, complete corrective surgery (arterial switch operation) is generally performed within 1–3 months after birth. When pulmonary blood flow is excessive, the timing of surgery and preoperative management differ.
• Post-procedure and postoperative care
  • Monitor for coronary artery stenosis and myocardial ischemia (echocardiography and, if necessary, CT/MRI coronary artery imaging).
  • Evaluate arrhythmias and left ventricular function, and conduct follow-up examinations for growth and motor development.
• Complication prevention and lifestyle management
  • Long-term follow-up after surgery (echocardiography, electrocardiography, and imaging tests) is recommended.
  • Follow the latest guidelines regarding infection (endocarditis) and other complications.

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Checklist Before an Outpatient Visit (Including Items to Bring and Sample Questions)

• Items to bring to the visit
  • A list of current medications (names and doses)
  • Birth records/surgical records (surgery name, operative report/discharge summary)
  • Results of recent echocardiography, electrocardiography, chest radiography, and CT/MRI examinations (originals or CDs if possible)
  • Resting oxygen saturation records or readings from a home pulse oximeter
  • Growth and feeding records (changes in weight and feeding volume)
  • Symptom diary: frequency and severity of cyanosis, timing of worsening dyspnea, fever, history of infections, etc.
• Information that should be reported immediately to the treating clinician during an outpatient visit
  • Recent rapid worsening of cyanosis or refusal to feed
  • Episodes of dyspnea or apnea
  • Fever or signs of infection (the risk of infection after surgery needs to be assessed)
• Test preparation (when instructed by the physician)
  • Oxygen status and blood gas analysis, echocardiography, and, if necessary, cardiovascular computed tomography or cardiac catheterization

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Examples of General Questions to Ask the Doctor

• "What emergency measures are needed immediately for this condition?"
• "If surgery (or a procedure) is recommended, when is the recommended timing?"
• "What are the expected success rate and short- and long-term complications of the surgery?"
• "Which tests are used to monitor the coronary arteries and ventricular function? How often?"
• "What restrictions will there be on daily life (feeding, vaccinations, and activities) after surgery?"

Examples of Condition-Specific Questions

• "Could you explain whether our baby’s coronary artery anatomy (branching pattern) is suitable for an arterial switch operation? If it is unsuitable, what are the alternatives?"
• "Is balloon atrial septostomy or prostaglandin treatment needed? If so, can it be performed immediately?"

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Additional Summary (Prognosis and Precautions)

• Prognosis: Without treatment, mortality in neonates and infants is very high (high mortality within the first several weeks to months has been reported in the natural course). With standard surgery such as an arterial switch operation, surgical and long-term survival rates are generally high, with rates of over 90% reported.
• Main precaution: When the condition is diagnosed prenatally, delivery at a medical institution capable of providing centralized care is recommended. Because transferring a newborn externally may worsen the condition, planned delivery and treatment are important.
• Long-term management: Lifelong follow-up is necessary because coronary artery stenosis, changes in ventricular function, arrhythmias, and other issues may occur even after surgery.

(If needed, I can organize more specific recommendations and directions based on the baby’s current test results or surgical records.)