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Patent Ductus Arteriosus

Normal duct provides 85% of aortic flow before birth. Rising PaO2 drives closure, acting via bradykinin & prostaglandins. PDA present in 0.02% of term babies. In preterm on the other hand, prostaglandin levels are high, endothelium lacks cushions that facilitate closure, plus sepsis/hypoxia interfere.

Degree of shunt depends on pulmonary vascular resistance (PVR), clinical effects depend on how well the overloaded heart can function. Associated with pulmonary haemorrhage, IVH, NEC. Associated with recurrent desaturations but only indirectly, due to high PVR with intemittent right to left shunting.

Diagnosis: continuous murmur (but not always heard), bounding pulses (a bit subjective). Echo shows large LA:Ao (left atrium to aortic root diameter ratio) eg >2, or colour flow may demonstrate. Best strategy is probably to search + destroy for the highest risk.

Management:

• No benefit from fluid restriction. But probably best to avoid excessive fluid administration.
• Indomethacin - 40% unresponsive, 35% recur anyway. SEs brain, gut, renal. 100mcg/kg? Ibuprofen also works but may be associated with more chronic lung disease!? Latter is preferred if concern about NEC (10mg/kg loading, 5 OD 2/7). Cochrane has lots of information.
• Oral ibuprofen works and with fewer adverse effects than IV indomethacin - But most over 28/40, and brave to start oral meds so early!? Pediatrics. 2008 122(6):e1256-61. PMID: 19047225
• Percutaneous coil closure - not suitable for the tiniest babies where coil can impinge on pulmonary artery flow
• Surgical closure

Medical treatment was associated with reduction in G3/4 IVH but in that study there was a high prevalence pre-intervention. Untreated tend to close spontaneously near term, if not many will remain asymptomatic.

Duct dependent lesions

ie no problem immediately at birth, but as duct begins to close eg 2-7 days, blood flow to distal aortic arch progressively reduced. Coarctation of aorta, hypoplastic left heart syndrome. Hence:

• Poor perfusion, shock
• Pale, grey rather than cyanosed, although sats usually reduced
• Poor peripheral pulses
• Sats in right arm (pre-ductal) better than in other limbs (post-ductal)

Differential is sepsis, inborn error of metabolism.

Treatment involves opening the duct again. 2 formulations of Prostaglandin E2 available: Alprostadil licensed, more expensive cf Dinoprost (unlicensed). Apnoea seen historically with prostaglandin, but usually at higher doses, and in 1st hour. So seems reasonable to transfer unventilated if otherwise well.

Balloon septostomy will obviate the need for a duct, pending definitive surgical treatment.

Congenital Long QT Syndrome

May present antenatally with fetal bradycardia. Highest risk for neonatal death are those who also demonstrate intermittent 2nd degree AV block and runs of VT. Heart. 1997 Mar;77(3):198-204. PMID: 9093034

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