The ductus arteriosus connects the pulmonary artery with the aorta, allowing blood to bypass the lungs. It usually stops functioning within three 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.
PDA is more common in premature babies. It may be related to a genetic condition (e.g., Down syndrome) or maternal condition (e.g., diabetes or rubella).
A small PDA may be asymptomatic, cause no functional problems and close spontaneously. Occasionally, patients can remain asymptomatic throughout childhood and present in adulthood.
Pathophysiology
Prostaglandin E2 (produced by the placenta) keeps the ductus arteriosus open during pregnancy. Prostaglandin E2 falls following birth, resulting in the closure of the ductus arteriosus.
The pressure in the aorta is higher than in the pulmonary vessels. Therefore, blood flows across a PDA from the aorta to the pulmonary artery. This is a left-to-right shunt, where blood from the left side of the heart crosses to the right-sided circulation and lungs.
Additional blood creates more pressure in the pulmonary vessels (pulmonary hypertension), leading to strain on the right ventricle. Pulmonary hypertension and right-sided heart strain lead to right ventricular hypertrophy.
The increased blood volume returning to the left side of the heart leads to left ventricular hypertrophy.
Presentation
A small patent ductus arteriosus may not have any abnormal heart sounds.
Larger PDAs cause a continuous crescendo-decrescendo “machinery” murmur, heard loudest below the clavicle. There is a normal first heart sound (S1), but the second heart sound (S2) may be difficult to hear over the murmur.
The murmur may be detected during the newborn examination.
It may also present with symptoms of:
- Shortness of breath
- Difficulty feeding
- Poor weight gain
- Lower respiratory tract infections
Management
An echocardiogram confirms the diagnosis.
Medical closure with indomethacin, ibuprofen, or paracetamol may be attempted in preterm infants. These medications work by inhibiting prostaglandins.
Closure of a PDA can be achieved by:
- Endovascular procedures (using a catheter inserted into a peripheral vessel and fed to the heart)
- Open surgery
Treatment for heart failure may be required (e.g., diuretics).
Last updated November 2024
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