Platypnea-Orthodeoxia Syndrome From Atrial Septal Defects: A Rare Primum Case and Literature Review.

Platypnea-orthodeoxia syndrome (POS) is characterized by hypoxemia that worsens in the upright position and improves when lying down. While various causes exist, most cases involve intracardiac shunting through a patent foramen ovale, whereas atrial septal defects (ASDs) are less common and present in diverse embryological forms. Most documented ASD-associated cases involve the secundum type, whereas the primum subtype remains notably rare in the literature. We report a rare case of POS caused by a primum ASD in a 68-year-old female. Transesophageal echocardiography was essential for locating the primum ASD, which facilitated successful percutaneous closure and complete resolution of her symptoms. Additionally, we reviewed 18 published cases of ASD-associated POS to better characterize the presentation, anatomical contributors, and treatment outcomes of this cause.