Reverse Platypnea–Orthodeoxia with Atrial Septal Defect and Diffuse Pulmonary Arteriovenous Fistulae in Hepatopulmonary Syndrome

A 69-year-old male with a long-standing diagnosis of interstitial lung disease and on domiciliary oxygen therapy was evaluated by echocardiography. His supine oxygen saturation ranged between 77% and 86% and upright oxygen saturation was 93%–94%. Two-dimensional transthoracic echocardiography showed a secundum atrial septal defect of 15 mm diameter with left-to-right shunting but without dilatation of right-sided chambers. Air bubble contrast echocardiography showed no air bubbles crossing the atrial septum but bubbles appeared in left-sided chambers through pulmonary veins after five cardiac cycles indicating intra-pulmonary shunting. Computed tomography of the chest demonstrated a mosaic pattern of the lung parenchyma, characterized by the presence of alternating geographic areas of low attenuation with regions of relatively increased attenuation typical of diffuse pulmonary arteriovenous fistulae. This is a rare case of reverse platypnea-orthodexia with possible contribution of two different pathophysiologic mechanisms but precise mechanism remains elusive.