Hypoxemia secondary to right-to-left interatrial shunt through a patent foramen ovale in a patient with an elevated right hemidiaphragm.

Though uncommon, right-to-left shunt through a patent foramen ovale with normal right-side pressure and with a normal interatrial pressure gradient has been reported. The speculated pathophysiology is attributed to directional blood flow streaming from the vena cava to the left atrium. Hypoxemia secondary to right-to-left shunt with normal pulmonary artery pressure has been extensively documented after right pneumonectomy. Five prior cases have documented hypoxemia secondary to a right-to-left shunt through a patent foramen ovale in the presence of an elevated right hemidiaphragm. This is the sixth documented case of right-to-left shunt through a patent foramen ovale in the presence of an elevated right hemidiaphragm with a similar presentation in which closure of the patent foramen ovale resulted in resolution of hypoxemia.