Congenital Heart Disease in the Emergency Department

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Patent Ductus Arteriosus (PDA)

The ductus arteriosus connects the pulmonary artery to the descending aorta. In term infants, it normally closes shortly after birth and is completely closed in most infants by 2 to 3 weeks of age.

When there is a failure of ductal constriction after birth, the ductus arteriosus remains patent. The flow of blood across a PDA is then from the aorta to the pulmonary artery (i.e. left to right Fig 3), following the fall in pulmonary vascular resistance after birth. In the preterm infant, the presence of a PDA is not from congenital heart disease but due to prematurity (since muscularization of the medial layer occurs primarily in the third trimester).

Fig 3: Patent ductus arteriosus

patentductus

Clinical presentation

Symptoms
  • Usually asymptomatic
  • When the duct is large there will be increased pulmonary blood flow with heart failure and pulmonary hypertension
Physical signs
  • A continuous machinery murmur left upper sternal border
  • Diastolic rumble: the murmur continues into diastole because the pressure in the pulmonary artery is lower than that in the aorta throughout the cardiac cycle.
  • In premature infants, a large ductus may only present with a flow murmur, or frequently, with no murmur. The diagnosis is suspected due to the requirement of increasing respiratory support.
  • The pulse pressure is increased, causing bounding pulses

Investigations

Chest radiograph
  • Usually normal
  • Cardiomegaly and increased pulmonary vascular markings (Large PDA)
ECG
  • Left and right ventricular hypertrophy (Large PDA)
Echocardiography
  • The duct is readily identified on echocardiography

Management

Surgical closure is the gold standard when indicated in the newborn period.

Indomethacin may be considered; it does, however, have the potential to cause necrotizing enterocolitis, intracranial hemorrhage, and renal toxicity.