Circulatory changes at birth and Eisenmenger syndrome
THE CONTEXT
The target passage describes the transition to pulmonary circulation at birth and the consequences of shunt reversal in prolonged pulmonary hypertension.
Circulatory transition at birth
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Expansion of the lungs with air lowers pulmonary vascular resistance, allowing blood to flow to the lungs and return to the left atrium.
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Left atrial pressure rises above right atrial pressure, closing the flap valve of the foramen ovale.
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The umbilical arteries and ductus venosus close.
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Over the next few days, hormonal changes, particularly involving prostaglandins, lead to ductus arteriosus closure, while the aortic isthmus expands.
Eisenmenger syndrome
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Severe, prolonged pulmonary hypertension may reverse a left-to-right shunt, producing a right-to-left shunt and marked cyanosis; this is Eisenmenger syndrome.
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Cyanosis may be more apparent in the feet and toes than in the upper body, producing differential cyanosis.
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Eisenmenger syndrome is more common with large ventricular septal defects or persistent ductus arteriosus than with atrial septal defects.
Risks and prognosis
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Eisenmenger syndrome is irreversible without heart and lung transplantation.
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Abrupt changes in afterload associated with vasodilatation, anaesthesia and pregnancy can exacerbate right-to-left shunting and pose particular risks.
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The long-term prognosis is poor: around 50% of young adults survive 10 years from diagnosis.