Case Presentation:

An 87–year–old female presented with weakness. She reported fatigue over several weeks, now unable to walk. She denied fever, chest pain, or shortness of breath. Past medical history includes CAD, DVT, hypertension, ophthalmic vein thrombosis. The patient was hypoxic with an O2 saturation of 84%, which improved to 93% with a non–rebreather (NRB). Her exam revealed clear lungs and a systolic murmur. Chest X–ray revealed bibasilar atelectasis. A CT Chest showed no acute airspace disease. An echocardiogram showed an EF of 35% and mild aortic stenosis. The patient was treated empirically for congestive heart failure and pulmonary embolism. It was noted during a manual disimpaction her oxygen saturation improved to 98% on room air. It was discovered that the patient did not require any oxygen if lying flat on her left side but required NRB when sitting up. Positional echo with agitated saline revealed a large intra–arterial septal aneurysm with predominant right–to–left bulging and minimal right–to–left flow when the patient was supine. Upright, the right–to–left shunting increased. TEE confirmed the findings. The patient underwent cardiac catheterization for closure of a secundum atrial–septal defect. Oxygen saturation immediately improved after the procedure, and the patient was breathing on room air upon discharge. Discussion: This patient was diagnosed with orthodeoxia–platypneasyndrome resulting from an atrial–septal defect. Orthodeoxia–platypnea syndrome can result from intra–cardiac shunting, intra–pulmonary shunting or VQ mismatch, and may be seen with normal or elevated right sided pressures. Any condition which causes elevated right sided pressure can cause right to left shunting of deoxygenated blood through an existing patent foramen ovale or atrial septal defect. Less well understood is the mechanism by which orthodeoxia–platypnea syndrome occurs without elevated right sided pressures. It has been postulated that the upright position may stretch the existing intracardiac defect, leading to increased blood flow from the inferior vena cava through the defect. This can also occur with a persistent Eustachian valve. Diagnosis of this condition may be initially missed due to normal findings in the supine position. Only when a positional echo was done with agitated saline, could the shunt be visualized. It is often necessary to obtain a transesophageal echo in order to better visualize the intra–atrial septum. Conditions associated with orthodeoxia–platypnea syndrome include pulmonary AVMs, hepatopulmonary syndrome, and constrictive pericarditis. Treatment for orthodeoxia–platypnea varies depending on etiology. When right heart pressures are normal, as they were with our patient, intra–cardiac closure devices can be employed with complete reversal of symptoms.

Conclusions:

When confronted with hypoxia that does not respond to oxygen, one should keep causes of intra–cardiac and intra–pulmonary shunt in the differential.