Patent ductus arteriosus

• The ductus arteriosus connects the pulmonary artery with the aorta, allowing blood to bypass the lungs. It usually stops functioning within 3-5 days of birth and closes entirely within the first three weeks of life.
• Patent ductus arteriosus (PDA) occurs when it fails to close after birth. The reasons it fails to close are unclear.
• Causes:

  • Much more common in premature babies
  • Can be related to a genetic condition e.g. Down's syndrome
  • Maternal conditions e.g. diabetes or rubella
• Pathophysiology:

  • Prostaglandin E2 (produced by the placenta) keeps the ductus arteriosus open during pregnancy - levels fall following birth, resulting in closure
  • Pressure in aorta is higher than in the pulmonary vessels - blood flows across PDA from the aorta to the pulmonary artery - left to right shunt
  • Leads to pulmonary hypertension and right ventricular hypertrophy
  • Can then lead to left ventricular hypertrophy
• Symptoms usually present 3-5 days after birth when the duct begins to close
• Symptoms depend on the size of the lesion:

  • Small - asymptomatic
  • Moderate - congestive heart failure with failure to thrive
  • Large - poor feeding, severe failure to thrive, recurrent LRTI (preterm infants may experience failure to wean from ventilation)
• Clinical features:

  • Palpate - palpable liver in heart failure, bounding pulses and wife pulse pressure
  • Auscultation - continuous machinery murmur typically heard at the upper left sternal border (best heard below the left clavicle), thrill at upper left sternal border
• Investigations:

  • Echocardiogram and doppler (most useful)
  • CXR and EXG are less useful
• Management:

  • Preterm - good probability of spontaneous closure - indomethacin/ibuprofen (inhibit prostaglandins)
  • Term - less likely to close spontaneously - closure - catheter closure or PDA ligation (thoracotomy)