Patent Ductus Arteriosus

Aetiology
Persistence of the ductus can occur as a result of relative hypoxaemia secondary to birth at hugh altitude, pulmonary atresia etc.
Risk factor: female, matermal rubella infection, prematurity
common in premature infants, often resolves as term is approached
Occurs in 60% of infants born prior to 28wk

Hereditary form- Char Syndrome (PDA, characteristic facial features, abnormal 5th digit)

Epidemiology

5-10% of all congenital heart disease

Pathophysiology

Oxygenation of fetal blood occurs in placenta, the ductus arteriosus (connecting the pulmonary artery to aorta) allows oxygenated blood from placenta to bypass the nun-functioning fetal lungs to enter systemic circulation.
After birth, oxygenation of blood occurs in the lungs, so ductus arteriosus is not required.
Flow through the ductus normally stops within 10-15h of birth, complete closure within 2-3 weeks
Closue reis mediated by a reduction in E-type prostaglandins, as well as the acute rise in arterial oxygen that occurs immediately following birth
If the ductus is not close as it should, blood flows from the aorta to the pulmonary artery as pulmonary vascular resistance decreases postnatally
A resultant left-to-right shunt causes pulmonary vascular congestion & ultimately, pulmonary vascular obstructive disease


Presentation

Continuous "machinery" murmur at the left upper sternal border (maximal at the midclavicular line

• Small defect- asymptomatic
• Moderate- CHF, tachypnoea, dyspnoea, poor feeding & growth, profuse sweating- crying, feeding
• Large- CHF unresponsive to ACEi & diuresis

Premature infants may have a large patient ductus arteriosus without a murmur

Active precordium & bounding pulses (wide pulse pressure)

DDx

Venous hum

coronary artery fistula

Aortic stenosis with associated aortic insufficiency

Systemic arteriovenous malformations

Pulmonary artery atresia with collateral circulation

Ventricular septal defect

Investigation

Clinical exam
ECG- varies, LVH, LAH, and/or RVH
CXR- cardiomegaly with increased pulmonary vascular markings, prominet aortic knob, LVH, LAH, large pulmonary artery

Echo+doppler =diagnostic
- colour doppler retrograde flow in the pulmonary arteries
- best images from suprasternal notch view
Cardiac catheterization with angiography

Management

The PDA can be closed by
- IV indomethacin - used in early infancy of premature infants, less effective in term infants, useful in treatment of premature infants with PDA complicating resp. distress syndrome
- IV ibuprofen can also be used,
- Surgical ligation, preferably done thoracoscopically. Tx of choice in infants who fail indomethacin therapy (surgery is generally delayed for at least 7 weeks in pt with concurrent endocarditis)
- Percutaeneous closure using coil embolisation

PDA-maybe useful in ceetain congenital conditions in which systemic circulation is compromised (aortic coarctation, hypoplastic left ventricle)

Prognosis

spontaneous closure in 1st week, delayed in prematurity