Platypnea-orthodeoxia

Platypnea-orthodeoxia is characterized by dyspnoea and systemic oxygen desaturation on assuming the sitting or standing position. It was originally described by Burchell et al in 1949 [Burchell HB et al. Reflex orthostatic dyspnea associated with pulmonary hypertension. Am J Physiol. 1949; 159: 563–564]. The basic requirement for the condition is an interatrial communication in the form of a patent foramen ovale, atrial septal defect or an atrial septal aneurysm with a fenestration. In addition there should be a mechanism which causes a reversal of flow across the interatrial septum. These additional factors which have been implicated include loculated pericardial effusion, constriction, emphysema, pulmonary arteriovenous malformation, cirrhosis liver and aortic aneurysm. A prominent eustachian valve is thought to play an important role in directing the inferior vena caval blood into the left atrium, even in the absence of pulmonary hypertension. Another factor considered is the stretching of the interatrial communication which occurs in the upright position which facilitates the streaming of inferior vena caval blood across the inter atrial defect into the left atrium. Treatment of course, is closure of the inter atrial communication either surgically or by trans catheter intervention [Medina A et al. Platypnea-orthodeoxia due to aortic elongation. Circulation. 2001; 104: 741 (free full text including echocardiographic images available online); Cheng TO. Platypnea-orthodeoxia syndrome: etiology, differential diagnosis, and management. Cathet Cardiovasc Interv. 1999; 47: 64–66].