Right atrial compression due to idiopathic right diaphragm paralysis detected incidentally by transthoracic echocardiography

Unilateral diaphragm paralysis (UDP) is an important and often unrecognized cause of dyspnea. We report a 72-year-old man in whom UDP was incidentally detected by transthoracic echocardiography. He was asymptomatic at rest, but experienced dyspnea on exertion. Chest radiography was not pathognomonic in this case because the heart silhouette obscured the left diaphragmatic contour. Transthoracic echocardiography showed an extrinsic compression to the right atrium. Right atrial collapse was obvious during heart movements with variation upon respiratory movements. There was no pericardial effusion nor any solid mass lesion. Fluoroscopic sniff test demonstrated a significant paradoxical elevation of the paralyzed right diaphragm in inspiration. Thoracic and abdominal computed tomography scans did not show any other pathology. The diagnosis was made as idiopathic UDP.