Neonatal Circulation
Patent foramen ovale
Patent ductus arteriosus and ductus venosus
Equal R/L pressures in heart
Highly oxygenated blood to brain and myocardium, less oxygenated blood to lower body.
Only 8% goes to lungs because pulmonary resistance is high
RV pumps 2/3 of output
Ductus venosus carries 40-60% of umbilical venous blood.
Crista dividens and Eustacian valve direct blood through foramen ovale.
Little volume crosses the aortic isthmus.
At Birth
- Pulmonary resistance drops > 50% of output
- Flow through PDA decreases
- Umbilical vessels constrict and close, peripheral resistance increases, ductus venosus closes
- Left atrial pressure increases
- Foramen ovale closes
- PDA reverses then ceases
CHD – 8/1000, 40% are VSDs
Signs:
- furrowed brow
- color
- respiratory effort – happy tachypnea
- murmur – ejection
- poor lower extremity pulses – coarctation – usually stable until PDA closes in a week.
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