“Worse With Sitting”: A Case of Severe Hypoxia Due to an Undiscovered Patent Foramen Ovale

Patent foramen ovale (PFO) is a cardiac shunt that results when the foramen ovale fails to close after birth. While it is relatively common, most cases are asymptomatic. The primary clinical implication of PFO is an increased risk of cryptogenic stroke. Accordingly, most literature addresses PFO through the lens of treating/preventing neurological disease. Much less research has been devoted to the minority of patients who suffer pulmonary and cardiovascular symptoms that are directly caused by their PFO. Here, we discuss a case of an elderly female patient presenting with hypoxia requiring high respiratory support, later found to be the result of a large, previously unknown PFO.