Platypnea-Orthodeoxia Syndrome: Two Case Reports.

Described for the first time in the middle of the last century, platypnea-orthodeoxia syndrome (POS) is an uncommon condition of positional dyspnea and hypoxemia, triggered by standing and relieved with recumbency. It is most commonly associated with right-to-left shunting through a patent foramen ovale (PFO) or atrial septal defect, however its pathophysiology is not entirely understood. As a rare syndrome, it remains underdiagnosed in many patients. We report two different cases that illustrate the challenge of this diagnosis and therapeutic approach. In the first case, a transesophageal echocardiogram (TEE) showed interatrial communication, ostium secundum type, with bidirectional shunting. Patient underwent a successful percutaneous closure of communication, with no residual shunting and clinical improvement and no positional hypoxemia. In the second case, infectious complications were the cause of hemodynamic changes producing meaningful right-to-left pressure gradients, resulting in POS. After antibiotic treatment there was a major clinical improvement and a second TEE showed bidirectional shunting with no positional variation. It was assumed resolution of POS after treatment of infectious complications with no need for immediate surgery. These two cases, with very distinctive functional and anatomic components, illustrate the challenge of understanding the exact mechanism by which POS results in clinical symptoms. A suggestive history and positional variation of oxygen saturation are very useful clues for its diagnosis in cases of unexplained hypoxemia.