["On and off" hypoxaemia]

Abstract

Introduction: A right to left shunt caused by a patent foramen ovale (PFO) must be considered when patients present with symptoms of platypnoea-orthodeoxia. The most useful investigation is saline contrast transthoracic or transoesophageal echocardiography.

Case report: We report a case of an eighty-year-old woman with the platypnoea-orthodeoxia syndrome, but without signs of a right to left shunt caused by a PFO. (99m)Tc-macroaggregated albumin lung scintigraphy and saline contrast transthoracic echocardiography were considered normal in the supine position. The clinical suspicion of PFO was so strong that the examinations were repeated in the upright position. This revealed a systemic uptake of the isotope on lung scintigraphy, confirmed by saline contrast echocardiography. The atrial septal defect was due to displacement of the interatrial septum by an aneurysm of the ascending aortic. In the upright position blood flowed directly from the inferior cava vena through a PFO into the left atrium.

Conclusion: The diagnosis of PFO may be difficult and it is important to repeat saline contrast echocardiography in the upright position when it is negative supine. It is possible to confirm the diagnosis by contrast infusion through the femoral veins.