SHM Converge Scientific Abstract ePoster Gallery-The Hidden Shunt: A Case of Platypnea-Orthodeoxia Syndrome Secondary to Atrial Septal Defect

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Platypnea-orthodeoxia syndrome (POS) is a rare, often underdiagnosed cause of positional dyspnea and hypoxemia that worsens when sitting or standing and improves when recumbent. This case describes a 72-year-old woman with unexplained upright desaturation (84%) but normal oxygenation when lying down (97%). Initial workup, including labs, pulmonary function tests, and cardiac catheterization, was largely normal except for evidence of a significant right-to-left shunt on echocardiography.<br /><br />Further testing identified the source as a small atrial septal defect with an atrial septal aneurysm and fenestrations. Cardiac CT and transcranial Doppler confirmed the shunt, which became more prominent upright and with Valsalva. Mild enlargement of the ascending aorta may have contributed to shunt reversal by altering atrial septal geometry in the upright position. The patient required supplemental oxygen while upright but remained otherwise asymptomatic.<br /><br />She underwent percutaneous closure with a 30 mm atrial septal occlusion device, after which her oxygen saturation stabilized at 96% without positional variation. Follow-up echocardiography showed no residual shunting, and she remained improved at 20 days and 4 months after the procedure.<br /><br />The report emphasizes that POS requires two elements: a shunt (intracardiac or extracardiac) and a positional/anatomic factor that drives right-to-left flow when upright. Diagnosis often depends on contrast-enhanced TTE or TEE with bubble study, ideally in both supine and upright positions. Treatment focuses on closing the underlying shunt, typically percutaneously for intracardiac defects such as PFO or ASD.

Asset Subtitle

Somanshu Sharma

Meta Tag

Author List Camille Hawkins, Somanshu Sharma

Category Clinical Vignettes

Concept Platypnea-Orthodeoxia Syndrome

Concept Positional Hypoxemia

Concept Dyspnea

Concept Right-to-Left Shunt

Concept Contrast-Enhanced Transthoracic Echocardiography

Distinguished Non-Finalist

Presenter Organization Mayo Clinic Alix School of Medicine - Arizona Campus

Presenting Author Somanshu Sharma

Track Adult

Keywords

platypnea-orthodeoxia syndrome

positional dyspnea

hypoxemia

right-to-left shunt

atrial septal defect

atrial septal aneurysm

bubble study

transcranial Doppler

percutaneous closure

upright desaturation

Platypnea-Orthodeoxia Syndrome

Positional Hypoxemia

Dyspnea

Right-to-Left Shunt

Contrast-Enhanced Transthoracic Echocardiography