Patent Ductus Arteriosus (PDA) Lecture Notes

Introduction

• PDA is a congenital heart defect characterized by the ductus arteriosus failing to close within the first few weeks of life.
• Ductus Arteriosus: An artery connecting the aorta and the pulmonary artery during fetal life that normally closes after birth.
• Failure to close results in PDA, creating a left-to-right shunt and increased pulmonary blood flow.

Causes and Risk Factors

• Most congenital heart defects have unknown causes.
• Risk Factors:
  • Premature birth (1 in 5)
  • Family history and genetic conditions (e.g., Down syndrome)
  • Rubella infection during pregnancy
  • Female gender (twice as common in females)
  • High altitude birth (due to hypoxemia-induced failure)

Pathophysiology

• Hemodynamic consequences depend on the duct size and pulmonary vascular resistance.
• At birth, resistance in pulmonary and systemic circulations is almost equal. Over time, systemic pressure exceeds pulmonary pressure, leading to blood shunting from the aorta to the pulmonary artery.
• Consequences:
  • Increased workload on the left side of the heart
  • Increased pulmonary vascular congestion/resistance
  • Potential increase in right ventricular pressure and hypertrophy

Clinical Manifestations

• Symptoms depend on the size of the PDA.
• Small PDA: May be asymptomatic.
• Large PDA: Symptoms may include:
  • Continuous machinery-like murmur
  • Endocarditis
  • Increased heart rate
  • Wide pulse pressure (difference > 15 mmHg in preterm, > 25 mmHg in term infants)
  • Activity intolerance, feeding trouble, poor weight gain, frequent chest infections

Diagnosis

• Auscultation: Listening for a continuous machinery-like murmur
• Echocardiography: Main diagnostic tool; estimates shunt volume and detects other defects
• X-Ray: May show left ventricle and pulmonary artery enlargement
• Cardiac Catheterization: Can reveal PDA
• ECG: May show changes such as T wave inversion and ST segment depression, especially in premature infants with large PDA

Treatment

• Pharmacological:
  • Indomethacin (NSAID) inhibits prostaglandin production and closes PDA in preterm infants
• Non-Surgical:
  • Cardiac catheterization with PDA closure device
• Surgical:
  • Surgical division and ligation via left thoracotomy

Nursing Management

• Monitor for signs of PDA in premature infants
• Regularly check vital signs, ECG, electrolyte levels, and input/output
• For indomethacin treatment, monitor for adverse effects (e.g., diarrhea, jaundice, renal dysfunction)
• Pre-operatively explain treatment and tests to parents
• Post-operatively assess signs, input/output, and provide pain relief
• Administer prescribed medications

Conclusion

• PDA requires careful diagnosis and appropriate treatment to manage and prevent complications.