The ductus arteriosus normally stops functioning within 1-3 days of birth, and closes completely within the first 2-3 weeks of life. When it fails to close, this is called a “patent ductus arteriosus” (PDA). The reasons why it fails to close are unclear, but it may be genetic or related to maternal infections such as rubella. Prematurity is a key risk factor.
A small PDA can be asymptomatic, cause no functional problems and close spontaneously. Occasionally patients can remain asymptomatic throughout childhood and present in adulthood with signs of heart failure.
The pressure in the aorta is higher than that in the pulmonary vessels, so blood flows from the aorta to the pulmonary artery. This creates a left to right shunt where blood from the left side of the heart crosses to the circulation from the right side. This increases the pressure in the pulmonary vessels causing pulmonary hypertension, leading to right sided heart strain as the right ventricle struggles to contract against the increased resistance. Pulmonary hypertension and right sided heart strain lead to right ventricular hypertrophy. The increased blood flowing through the pulmonary vessels and returning to the left side of the heart leads to left ventricular hypertrophy.
A patent ductus arteriosus can be picked up during the newborn examination if a murmur is heard. It may also present with symptoms of:
- Shortness of breath
- Difficulty feeding
- Poor weight gain
- Lower respiratory tract infections
A small patent ductus arteriosus may not have any abnormal heart sounds. More significant PDAs cause a normal first heart sound with a continuous crescendo-decrescendo “machinery” murmur that may continue during the second heart sound, making the second heart sound difficult to hear.
The diagnosis of PDA can be confirmed by echocardiogram. The use of doppler flow studies during the echo can assess the size and characteristics of the left to right shunt. An echo is also useful for assessing the effects of the PDA on the heart, for example demonstrating hypertrophy of the right ventricle, left ventricle or both.
Patients are typically monitored until 1 year of age using echocardiograms. After 1 year of age it is highly unlikely that the PDA will close spontaneously and trans-catheter or surgical closure can be performed. Symptomatic patient or those with evidence of heart failure as a result of PDA are treated earlier.
Last updated July 2019