Platypnoea orthodeoxia in a patient with aortic root dilatation and a patent foramen ovale.

Platypnoea orthodeoxia syndrome is a rare condition in which shortness of breath and hypoxaemia occur when upright and resolve when prone. The hypoxaemia results from increased right to left shunting of deoxygenated blood, when standing, through a patent foramen ovale (PFO), atrial septal defect (ASD) or other right to left shunt, in the absence of raised right-heart pressure. We present the case of a patient with platypnoea orthodeoxia with marked shunting through a large PFO, evaluated by transesophageal and transthoracic echo.