Overview
The ductus arteriosus is a blood vessel in the foetus that usually closes shortly after birth (around 48 hours). It connects the pulmonary artery to the aorta to allow blood to pass the lungs in utero. Prostaglandins from the placenta keep the ductus arteriosus open, therefore, removal of the placenta facilitates its closure as the infant takes its first breath.
Patent ductus arteriosus (PDA) describes when this vessel remains open.
Epidemiology
- PDAs are very common in premature babies
- PDAs are nearly twice as common in females than in males
Risk Factors
- Prematurity
- Maternal rubella infection in the first trimester
- Birth at high altitude – due to lower oxygen levels
Presentation
The presence of features depends on the size of the PDA. Features include:
- A continuous ‘machinery’ murmur below the clavicle that may radiate to the back
- A left subclavian thrill may be felt
- Wide pulse pressure
- Tachycardia
- Tachypnoea
- Non-specific symptoms including irritability, poor feeding, and failure to thrive
- Differential cyanosis – cyanosis of the lower extremities but not the upper body
- Features of Eisenmenger syndrome
Investigations
Investigations include:
- ECG:
- Provides evidence of heart chamber hypertrophy
- Chest x-ray:
- May show cardiomegaly
- Echocardiography – diagnostic test of choice:
- Visualises PDA
Differential Diagnoses
Atrial septal defect
- The murmur heard tends to be ejection systolic and S2 has a wide and fixed (does not change with breathing) split.
Ventricular septal defect
- The murmur heard tends to be a pansystolic murmur
Patent ductus arteriosus
- The murmur tends to be a continuous systolic and diastolic ‘machinery-like’ murmur
- A left subclavian thrill may be felt
Management
Premature infants
Since prostaglandins keep the ductus arteriosus open, NSAIDs (which inhibit prostaglandin synthesis) such as indomethacin or ibuprofen are given to the neonate to facilitate its closure.
Other options include surgical correction or percutaneous catheter device closure.
Term infants
NSAIDs such as indomethacin and ibuprofen are generally ineffective in term infants and are not used. Options include:
- Surgical correction
- Percutaneous catheter device closure
- Management of heart failure (e.g. using loop diuretics)
Complications
Congestive heart failure
Shunting of blood between the left and right sides of the heart leads to increased strain and hypertrophy, negatively impacting the heart’s function as a pump.
Eisenmenger syndrome
Left-to-right shunting increases the pressure in the pulmonary vasculature resulting in pulmonary hypertension. This puts more strain on the right ventricle, which results in right ventricular hypertrophy and increased pressure on the right side of the heart.
Eventually, this exceeds the pressure on the left side of the heart, and the shunt is reversed, resulting in deoxygenated blood flowing from the right to the left side and entering the systemic circulation, bypassing the lungs. This leads to cyanosis and clubbing.
The development of Eisenmenger syndrome is an indication for a heart-lung transplant.
Prognosis
- In premature infants, using NSAIDs to close the PDA lead to successful closure in around 80% of cases
- Spontaneous closure of a PDA is rare
