Is altitude friend or foe in unrepaired congenital heart disease? A case report.

Background: Some unrestrictive congenital shunts put patients at high risk for developing irreversible pulmonary vascular disease if not closed in the first year of life. Living at high altitude also places patients at risk for developing pulmonary hypertension. There are anecdotal data that living at high altitude may be protective against the development of shunt-related pulmonary vascular disease.

Case summary: A 20-year-old female from Ecuador was found to have a large patent ductus arteriosus (PDA) and pulmonary hypertension after a murmur was auscultated. She had been living at altitude until 6 months prior. She was found to have a large PDA, systemic pulmonary artery (PA) pressure, and an elevated pulmonary vascular resistance index (PVRi) (33 wu ∗ m²) with minimal shunting (Qp:Qs 1:1). Vasodilatory testing with inhaled nitric oxide (iNO) and 100% FiO2 showed continued systemic PA pressure but a dramatic decrease in PVRi (12.5 wu ∗ m²) with an increase in left-to-right shunt (Qp:Qs 2:1). Living at high altitude causes hypoxic vasoconstriction. This vasoconstriction, which is typically reversible on descent to sea level, may decrease the left-to-right shunt and the irreversible downstream vascular changes that would normally occur in the setting of an unrestrictive PDA. Given the significant acute drop of this patient's vascular resistance with pulmonary vasodilator testing, she was started on oral pulmonary vasodilators. However, months later, the patient became increasingly symptomatic and repeat catheterization showed worsening cardiac function. Pulmonary vasodilators were stopped and the decision was made not to close the PDA.

Discussion: Living at high altitude may be protective against the development of congenital shunt-related irreversible pulmonary vascular disease. However, in this case, it may not have been enough due to the complexity of anatomy.