Patent Ductus Arteriosus Flashcards
What is a Patent Ductus Arteriosus (PDA)?
The persistence of the ductus arteriosus after birth
What is the Ductus arteriosus?
A vascular connection between the pulmonary artery and the aortic arch
What is the function of the ductus arteriosus?
To shunt blood from the right to the left to bypass the foetus’ lungs
Why should blood bypass the lungs?
In the foetus they are compressed and filled with fluid
When does the DA usually begin to close?
In the first 48 hours of life
What is considered a PDA?
When the shunt has failed to close by 1 month after expected delivery date
What causes the DA to usually close?
- Reduced pulmonary vascular resistance
- Bradykinin causing constriction of the smooth muscle of the DA
What causes the reduced pulmonary vascular resistance?
When the newborn takes a first breath and the lungs open
Where is the bradykinin released from?
The lungs
When is the DA normally significantly narrowed?
12-24 hours after birth
When is the DA normally completely sealed?
3 weeks
What causes the DA to remain open in PDA?
A defect in the constrictor mechanism of the duct
Why is PDA not considered a cyanotic congenital defect?
The flow of blood reverses and moves from the aorta to the pulmonary artery
What are the risk factors for PDA?
- Prematurity
- Maternal rubella
- Respiratory distress syndrome
- High altitude
What do most children with PDA present with?
A continuous murmur beneath the left clavicle which continues into diastole
Why is the murmur present in PDA?
The pressure in the pulmonary artery is lower than in the aorta throughout the cardiac cycle
Are symptoms common in PDA?
No, they are unusual
What happens in PDA if the duct is large?
There will be increased pulmonary flow causing heart failure and pulmonary hypertension
What are some rarer signs and symptoms of PDA?
- Tachypnoea
- Failure to thrive
- Exercise intolerance
- Widened pulse pressure
What investigation can be used to diagnose PDA?
Echo
What are the signs on CXR and ECG in PDA?
Usually normal
What are the differentials for PDA?
- Venous hum
- Coronary artery fistula
- Left-sided shunts including VSD and ASD
What is the recommended treatment for PDA?
Closure of the duct
Why is PDA closure recommended?
To prevent the risk of bacterial endocarditis and pulmonary vascular disease
How is PDA closure carried out?
With a coil or occlusion device introduced via a cardiac catheter
When is PDA closure usually performed?
At around 1 year of age
What other surgical treatment is sometimes required?
Surgical ligation
What are the potential complications of PDA?
- Congestive heart failure
- Eisenmenger’s syndrome
- Pulmonary hypertension
