What is Patent Ductus Arteriosus (PDA)

Patent Ductus Arteriosus - PDA Patent ductus arteriosus (PDA) is a condition where a temporary blood vessel near an unborn baby’s heart, the ductus arteriosus, fails to close after birth. (The blood vessel normally closes after birth because it is no longer needed). The word “patent” means open.

Statistics on Patent Ductus Arteriosus (PDA)

About 1 in 2000 live births.

Risk Factors for Patent Ductus Arteriosus (PDA)

The aetiology (causes or origins) of congenital heart defects are not understood, but several factors are known to be associated:

(1) Maternal drug abuse, alcohol abuse and radiation exposure.
(2) Maternal infection, particularly rubella.
(3) Genetic abnormalities
(4) Chromosomal abnormalities (septal defects are associated with Trisomy 21- Down’s syndrome)

Progression of Patent Ductus Arteriosus (PDA)

The ductus arteriosus serves to bypass the lungs in fetal circulation and usually closes in response to high oxygen tensions after birth.

In sizeable defects blood is shunted from the aorta to the pulmonary vessels. This is due to the higher pressures in the systemic circulation. This produces a volume load on the left ventricle which leads to heart failure and lung congestion.

In the longer term, increased flow rates through the pulmonary (lung) circulation lead to pulmonary fibrosis (leading to non-functioning lung) and pulmonary hypertension.
In advanced severe disease, the pulmonary artery pressure can exceed the aortic pressure causing reversal of the shunt and cyanosis – a poor prognostic factor.

How is Patent Ductus Arteriosus (PDA) Diagnosed?

Chest x-ray: the aorta and pulmonary arteries may be prominent radiologically. There may be evidence of left ventricular dilatation.
ECG: may show evidence of left atrial and left ventricular abnormality (hypertrophy and dilatation).

Prognosis of Patent Ductus Arteriosus (PDA)

The majority of mortality and morbidity associated with PDA are due to heart failure. Irreversible pulmonary vascular damage and pulmonary hypertension are associated with poor prognoses but are uncommon in the first few years of life.

How is Patent Ductus Arteriosus (PDA) Treated?

Premature babies in whom the duct has not yet closed should be treated conservatively with indomethacin (an anti-inflammatory drug) which inhibits prostaglandins and promotes duct closure.

In other cases the ductus should be closed surgically or angiographically as early as possible.

Patent Ductus Arteriosus (PDA) References

[1] Anderson et al. Paediatric Cardiology. Churchill Livingstone 1987.
[2] Behrman, Kliegman, Jenson. Nelson Textbook of Paediatrics 17th Ed. Saunders 2004.
[3] Hurst’s The Heart 8th Edition, McGRAW-HILL 1994.
[4] Kumar and Clark, Clinical Medicine 4th Edition, W.B SAUNDERS 1998.
[5] Rudolph et al. Rudolphs’s Paediatrics (21st edition). McGraw-Hill 2003.