Platypnea-Orthodeoxia Syndrome Post-Pneumonectomy: A Case of Right-To-Left Shunting and Successful PFO Closure.

Platypnea-orthodeoxia syndrome is a rare disorder characterized by dyspnea (platypnea) and arterial desaturation (orthodeoxia) in the upright position, with symptom relief upon lying down. This syndrome is commonly associated with cardiac anomalies, particularly patent foramen ovale (PFO), where increased right atrial pressure facilitates right-to-left shunting, leading to hypoxemia. Other associated conditions include cirrhosis, pericardial effusion, and pneumonectomy. We present a 32-year-old female with a history of right pneumonectomy for invasive aspergillosis who presented with worsening dyspnea and a greater than 10% drop in SpO2 when seated compared to the supine position. Initial imaging demonstrated rightward displacement of thoracic structures, including the right atrium, but a transthoracic echocardiogram was negative for intracardiac shunt. Due to persistent hypoxemia, a transesophageal echocardiogram was performed, revealing a right-to-left shunt, an atrial septal aneurysm, and a prominent Eustachian valve. The patient underwent successful PFO closure, leading to the complete resolution of both dyspnea and hypoxemia. This case emphasizes the importance of comprehensive diagnostic evaluation in patients with POS, especially those with complex cardiopulmonary histories.