Patent Ductus Arteriosus (PDA)

• Patent ductus arteriosus (PDA) is a congenital heart defect that occurs when the ductus arteriosus, a blood vessel connecting the pulmonary artery to the aorta in the fetus, fails to close after birth

Overview

• In fetal circulation, the ductus arteriosus allows blood to bypass the non-functioning lungs and go directly to the aorta, and subsequently the rest of the body
• After birth, when the baby starts breathing, the ductus arteriosus is supposed to close, typically within a few days or weeks of life
• If the ductus arteriosus remains open (patent), blood can flow abnormally from the aorta to the pulmonary artery, leading to a variety of complications

Incidence and Risk Factors

• PDA is more common in premature infants, especially those born before 30 weeks of gestation, because their ductus arteriosus is less likely to close spontaneously
• Other risk factors include:
  • Maternal rubella infection during pregnancy
  • Genetic conditions such as Down syndrome
  • High altitude births
  • Certain medications taken during pregnancy

Pathophysiology

• In PDA, blood shunts from the high-pressure aorta to the low-pressure pulmonary artery
• This left-to-right shunt increases pulmonary blood flow and volume overload to the left atrium and ventricle
• Prolonged or large PDA can lead to:
  • Pulmonary hypertension (increased pressure in the pulmonary arteries)
  • Heart failure (the heart's inability to pump enough blood to meet the body's needs)
  • Increased risk of endocarditis (infection of the heart's inner lining)

Clinical Manifestations

• Symptoms of PDA vary depending on the size of the ductus arteriosus and the gestational age of the infant
• Small PDA may be asymptomatic
• Larger PDA can cause:
  • Heart murmur: a continuous, machine-like murmur is typically heard on examination
  • Rapid breathing or shortness of breath
  • Poor feeding and weight gain
  • Sweating with feeds
  • Fatigue
  • Bounding peripheral pulses
  • Widened pulse pressure
  • Signs of heart failure which can include edema, enlarged liver, and respiratory distress

Diagnosis

• Physical Examination: Auscultation of a characteristic heart murmur is often the first clue
• Echocardiogram: This ultrasound of the heart is the primary diagnostic tool
  • It visualizes the ductus arteriosus, assesses its size, and estimates the amount of blood shunting through it
  • It also helps evaluate the impact on heart chamber sizes and function
• Chest X-ray: May show increased pulmonary blood flow and heart enlargement
• Electrocardiogram (ECG): Usually normal in isolated PDA but may show signs of left ventricular hypertrophy with large shunts

Treatment

• Management of PDA depends on the infant's age, gestational age, symptoms, and the size of the PDA
• Options include:
  • Conservative Management:
    • Monitoring: In premature infants with small PDA, a "wait and see" approach may be adopted
    • Fluid Restriction: Reducing fluid intake can help minimize pulmonary edema
    • Respiratory Support: Supplemental oxygen or mechanical ventilation may be needed
  • Medical Management:
    • Nonsteroidal Anti-Inflammatory Drugs (NSAIDs):
      • Indomethacin or ibuprofen can be used to inhibit prostaglandin production, which promotes ductal closure
      • These medications are most effective in premature infants
      • Contraindications include renal dysfunction, bleeding disorders, and necrotizing enterocolitis
  • Surgical Management:
    • Surgical Ligation: Involves surgically closing the PDA with sutures or clips through a thoracotomy (surgical incision in the chest)
    • This is typically reserved for cases where medical management fails or is contraindicated
  • Catheter-Based Closure:
    • A minimally invasive procedure where a device is deployed through a catheter to occlude the PDA
    • Preferred approach for older infants and children with larger PDAs

Prognosis

• The prognosis for infants with PDA is generally good, especially with early diagnosis and appropriate treatment
• Small PDAs may close spontaneously or remain asymptomatic
• Larger PDAs that are left untreated can lead to significant complications, including pulmonary hypertension and heart failure
• Outcomes are generally better with catheter-based closure compared to surgical ligation, particularly in terms of reduced morbidity and shorter hospital stays

Potential Complications

• Heart failure
• Pulmonary hypertension
• Endocarditis
• Arrhythmias
• Growth retardation
• Necrotizing enterocolitis (in premature infants)
• Renal dysfunction (secondary to medications)
• Complications related to surgical or catheter-based interventions