Right-to-left interatrial shunt despite normal pulmonary artery pressure. Anatomical implications.

Platypnea-orthodeoxia is a rare syndrome characterized by dyspnea induced by the upright position and relieved by supine position and an arterial deoxygenation increased by the upright position which improves during recumbency. In many cases, this syndrome has been associated with patent foramen ovale and right-to-left shunt. Several anatomical factors that can alter the atrial anatomy and facilitate shunting through an interatrial communication have been related with this syndrome.