Patent foramen ovale causing refractory hypoxemia after off-pump coronary artery bypass: a case report.

Patent foramen ovale (PFO) is not uncommon in the adult population undergoing cardiac surgery. Although usually innocent, PFO can cause severe hypoxemia, which can be reversed only by surgical or interventional interruption of the interatrial right-to-left shunt. Such a case is presented, and the diagnosis and pathophysiology are discussed.