Platypnea-Orthodeoxia Syndrome Diagnosed Using Contrast Transesophageal Echocardiography With Simultaneous Spo(2) Monitoring

Platypnea-orthodeoxia syndrome (POS) is a rare condition characterized by interatrial right-to-left shunting that is exacerbated in the upright position. We herein report a 78-year-old woman with POS that remained undiagnosed for 2 years, despite repetitive transthoracic echocardiography (TTE). POS was ultimately diagnosed using contrast transesophageal echocardiography (TEE), which revealed a marked increase in right-to-left shunting in the sitting position, associated with simultaneous desaturation. Therefore, we propose that POS should be considered according to the clinical symptoms, regardless of the repetitive TTE results, and contrast TEE should be performed in both the supine and sitting positions to exclude a diagnosis of POS.