A Case of Platypnea-Orthodeoxia Syndrome in a Patient with a Pulmonary Arteriovenous Fistula and a Patent Foramen Ovale

We describe a case of a rare clinical disorder, platypnea-orthodeoxia syndrome. A 57-year-old man was admitted with progressive dyspnea. While breathing room air, arterial oxygen saturation decreased from 92% in a recumbent position to 83% in an upright position. Transthoracic echocardiography revealed normal left and right ventricular function, but intravenous infusion of air-blood-saline resulted in the appearance of microbubbles in the left side of the heart, indicating the presence of right-to-left shunt. Transesophageal echocardiography demonstrated a small amount of right-to-left shunting through a patent foramen ovale. Further, the left lower pulmonary vein was dilated, and contrast echocardiography revealed drainage of microbubbles mainly from the left lower pulmonary vein. A pulmonary angiogram revealed the presence of a pulmonary arteriovenous fistula. The patient underwent embolization of the arteriovenous fistula with subsequent resolution of dyspnea and hypoxemia. Platypnea-orthodeoxia syndrome is rare, and patients with this syndrome require an extensive workup to determine its cause.