Abstract Introduction Platypnea-orthodeoxia syndrome (POS) is a rare disorder characterized by positional dyspnea and hypoxemia from right-to-left shunting. POS is often associated with intracardiac defects such as a patent foramen ovale (PFO) but may also arise from extracardiac causes including pulmonary arteriovenous malformations (AVM). However, extrinsic anatomic factors, such as ascending thoracic aortic aneurysms (ATAA), or physiologic factors like pulmonary hypertension, can precipitate right-to-left shunting in previously asymptomatic individuals. We present a case of POS secondary to a PFO and interatrial septal aneurysm (ISA) in the setting of an ATAA compressing the right atrium in a previously asymptomatic patient. Case Presentation A 66-year-old male with no prior medical history was admitted for dizziness, nausea and dyspnea, during which a 5.3 x 5.7 cm ATAA and PFO were discovered. He required supplemental oxygen, though no cause of hypoxemia was found. Six weeks later, he re-presented with progressive presyncope and weakness that occurred upon standing. On arrival, oxygen saturation was 85% while upright and 97% when recumbent on high-flow nasal cannula at 60 L/min and 100% fraction of inspired oxygen. Physical exam was notable for vertical diplopia, anisocoria, and impaired convergence, and brain magnetic resonance imaging (MRI) revealed acute bilateral thalamic infarcts, likely embolic. Chest computed tomography angiography (CTA) revealed a stable ATAA compressing the right atrium without other pulmonary pathology. Supine and upright transthoracic echocardiography (TTE) bubble studies demonstrated an ISA and a moderate right-to-left shunt across the PFO that became more severe when upright, confirmed with transesophageal echocardiography (Figure 1). Right and left heart catheterizations revealed normal filling pressures and no left-to-right shunt. Percutaneous PFO closure was performed and led to immediate normalization of oxygen requirements and resolution of symptoms. The patient was discharged without supplemental oxygen with plans for semi-urgent ATAA repair. Discussion Platypnea-orthodeoxia syndrome is an uncommon but important cause of positional hypoxemia, and clinicians should be mindful of concomitant anatomic and physiologic factors that may facilitate right-to-left shunting. In this case, we suspect right atrial compression from the ATAA likely redirected venous return across the PFO, leading to POS. Since this previously asymptomatic patient’s hypoxemia and presyncope resolved immediately following percutaneous PFO closure, recognition of contributing factors is important, as intervention can resolve shunting and help prevent further complications. This abstract is funded by: None
Ranger et al. (Fri,) studied this question.