Platypnea-Orthodeoxia Syndrome Associated With a Right-to-Left Cardiac Shunt Detected by Lung Perfusion Scintigraphy

BACKGROUND Platypnea-orthodeoxia syndrome is a rare condition characterized by posture-dependent right-to-left shunting, resulting in dyspnea in the upright position that improves when supine. Diagnosis usually relies on echocardiographic microbubble testing or transesophageal echocardiography, which require patient cooperation and cardiology support and may be impractical in older or psychiatric patients. Lung perfusion scintigraphy provides a practical, noninvasive alternative for detecting shunts without requiring cooperation or cardiologist involvement. This report describes a case of platypnea-orthodeoxia syndrome associated with a right-to-left cardiac shunt that was detected by lung perfusion scintigraphy. CASE REPORT A 64-year-old woman with hypertension and severe bipolar disorder was admitted after being found unconscious. She displayed persistent hypoxemia despite oxygen supplementation. Laboratory findings were unremarkable; imaging revealed a dilated aortic root compressing the right atrium but no evidence of pulmonary embolism or pneumonia. Transthoracic echocardiography showed no definitive shunt. Microbubble testing or transesophageal echocardiography could not be performed due to psychiatric instability and lack of immediate cardiology support. On hospital day 2, lung perfusion scintigraphy demonstrated a right-to-left shunt, whereas chest computed tomography excluded intrapulmonary shunting. Cardiac catheterization on day 5 confirmed a patent foramen ovale with right atrial compression, establishing the diagnosis of platypnea-orthodeoxia syndrome. Shunt closure was deferred due to the unavailability of a specialist for percutaneous closure. At 12 months of follow-up, the patient remained untreated. CONCLUSIONS Lung perfusion scintigraphy represents a noninvasive and effective diagnostic tool for identifying intracardiac shunting in patients with unexplained hypoxemia when microbubble testing or transesophageal echocardiography is not feasible.