Case Presentation: A 72-year-old female with past medical history of GERD, mild obstructive sleep apnea, insomnia, and restless leg syndrome was directly admitted from outpatient Pulmonology Clinic to the inpatient hospital service due to hypoxia. Upon hospital admission, the patient’s hypoxemia was more prominent when sitting up (84%) as opposed to the recumbent position (97%). The patient had no prior hypoxic episodes. Physical exam revealed no abnormalities. All labs were within normal range. TTE with an added shunt study was performed, which disclosed a prominent right-to-left shunt at both rest and with Valsalva maneuver. She underwent a TEE which showcased an atrial septal aneurysm with fenestrations, as well as a mildly enlarged mid ascending aortic diameter. Her right and left cardiac catheterization showed a normal pulmonary artery pressure. Repeated pulmonary function tests were normal. She remained asymptomatic but required 5L oxygen via nasal cannula when upright. After discharge, a CT cardiac angiogram showed two 1-2 mm atrial septal defects on the superior aspect of her fossa ovalis with associated shunting. A transcranial doppler was performed in the supine, sitting, and standing positions, which showed a grade 4 right-to-left shunt that was more prominent when sitting and standing compared to the supine position, and was augmented with Valsalva maneuver. The patient was diagnosed with platypnea-orthodeoxia syndrome. The patient’s atrial septal defect was corrected with a 30 mm atrial septal occlusion device. Afterwards, the patient maintained stable oxygen saturation of 96% without positional variation and TTE demonstrated no residual interatrial shunting. At her follow-up cardiology visits 20 days and 4 months after her procedure, she demonstrated normal oxygen saturations and no residual shunting.
Discussion: Platypnea-orthodeoxia Syndrome (POS) is a rare condition characterized primarily by upright positional dyspnea (platypnea) and hypoxemia (orthodeoxia). This case showed that the presentation of this condition can vary from being clinically asymptomatic, to episodic dyspnea, to profound debilitating hypoxemia and platypnea, thus making the diagnosis challenging. A high degree of clinical suspicion for POS is imperative for patients exhibiting evidence of desaturation when going from the recumbent to upright positions. Two conditions must be met for a patient to present with POS. First, they must have an intracardiac or extracardiac shunt. Second, there must be a functional or anatomical condition causing right-to-left shunting of blood, which is exacerbated by upright position. A shunt study is imperative to show that blood is being shunted right-to-left and the number of cardiac cycles that it takes for the study to be positive can help inform whether the shunt is intracardiac or extracardiac. TTEs performed without shunt studies can often miss this elusive diagnosis. Ultimately, the treatment of POS involves closure of the underlying shunt. As in this case, close follow-up with a cardiologist is recommended to monitor for persistent symptoms or re-emergence of the shunt.
Conclusions: Platypnea-orthodeoxia Syndrome is a rare and often underdiagnosed condition that presents as dyspnea and hypoxemia when going from the recumbent to upright position. Clinical suspicion for POS should remain high in any patient presenting with persistent unexplained positional hypoxemia, even if asymptomatic.