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Introduction

Patent Ductus Arteriosus – PDA – L-to-R shunt – ACYANOTIC
Patent ductus arterioles describes the persistence of the connection between the aorta and pulmonary artery. In the foetus, this duct allows blood to bypass the pulmonary circulation, as oxygenation occurs via the placenta.
Shortly after brith, this uses closes physiologically, but in a small proportion of individuals, this does not occur, and hence a patent ductus arterioles persists.

It typically presents with failure to thrive and poor feeding, occasionally with tachypnoea and tachycardia. It causes a continuous murmur at the left sternal edge.

It is diagnosed with echocardiography.

Many close spontaneously, but if the defect persists, then it is closed either via catheter procedure or surgery. If left untreated, large PDAs may result in heart failure.

Patent ductus arteriosus

Patent ductus arteriosus. This file is taken from wikimedia commons and is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

Pathophysiology

The ductus arterioles is a normal anatomical feature in the foetus and is necessary for normal foetal circulation. At birth, the rise is PaO2 and a decline in prostaglandins normally causes a physiological closing of the duct, typically within the first 10-15 hours of life. 

The extent of the symptoms and disease that can result from a PDA depend on the size. Small PDAs may be asymptomatic, whilst larger ones can lead to pulmonary hypertension, heart failure and Eisenmenger’s syndrome.

Presentation

Small PDAs may be asymptomatic. Larger PDAs may present as:

  • In premature infants:
    • Respiratory distress
    • Apnoea
    • Critically unwell
  • In other infants and children – signs of heart failure:
    • Tachycardia
    • Tachypnoea
    • Poor feeding
    • Failure to thrive
    • SOB on feeding

Signs

  • Small PDAs often produce no signs
  • Continuous murmur at the left sternal edge may be heard

Diagnosis

In an infant with signs of heart failure, then further investigation is required to make the diagnosis. Differentiating between types of congenital heart disease clinically is very difficult.

  • Echocardiogram is the diagnostic test
  • ECG and CXR may be performed, but are usually normal unless the disease is very severe, in which case you may see:
    • Enlarged heart on CXR
    • Signs of left ventricular hypertrophy on ECG

Management

  • Usually treated even if asymptomatic to reduce the risk of infective endocarditis
  • Often involves cardiac catheterisation whereby a coil is introduced to the PDA, and used to close it.
  • Most commonly treated around 1 year of age
    • May be treated sooner if heart failure starts to develop
  • In premature infants, a prostaglandin inhibitor – such as indomethacin (an NSAID) can be used to stimulate closure. This is not usually effective in babies born at term.

References

  • Murtagh’s General Practice. 6th Ed. (2015) John Murtagh, Jill Rosenblatt
  • Oxford Handbook of General Practice. 3rd Ed. (2010) Simon, C., Everitt, H., van Drop, F.
  • Beers, MH., Porter RS., Jones, TV., Kaplan JL., Berkwits, M. The Merck Manual of Diagnosis and Therapy

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