An Unusual Case of Hypoxia: A Case of Right-to-Left Interatrial Shunting in a Patient With a Patent Foramen Ovale and Normal Pulmonary Pressure

A patent foramen ovale (PFO) is an embryological remnant. Hypoxia in the setting of a PFO is generally attributed to pulmonary hypertension resulting in an increase in right atrial pressure and mixing of venous blood from the right atrium with blood in the left atrium resulting in a right-to-left interatrial shunt (RLIAS), thus deoxygenating it. We present a case of a 64-year-old male with a past medical history of coronary artery disease (CAD) who presented with two weeks of dyspnea on exertion and intermittent chest pressure. He was found to be hypoxic at 87% (normal >95%) with largely normal workup except for left anterior descending (LAD) stenosis, which was stented, and a PFO that was found on transesophageal echocardiogram with normal pulmonary artery pressure (PAP). This case of hypoxia in the setting of a PFO without pulmonary hypertension puts into question the pathophysiology of hypoxia in a PFO and RLIAS.