Interplay of patent foramen ovale and atrial septum aneurysm in a nonagenarian patient presenting with platypnoea-orthodeoxia syndrome.

Patent foramen ovale (PFO) is a common congenital cardiac anomaly, generally responsible for cryptogenic stroke. Still, it can cause severe positional hypoxia via a right-to-left shunt if associated with anatomic distortion of the interatrial septum. A man in his 90s with a known atrial septal defect (pulmonary blood flow/systemic blood flow (Qp/Qs) ratio of 0.85) and ascending aortic aneurysm presented with sudden worsening of chronic exertional dyspnoea and had profound hypoxia, requiring bilevel positive airway pressure. Workup was negative for pulmonary embolism with an unremarkable prior transthoracic echocardiogram (TTE). During hospitalisation, he was found to have worsening hypoxia in the upright position, which improved in the supine and right lateral decubitus positions. A repeat TTE with agitated saline was performed, which showed a PFO with a large right-to-left shunt, confirmed by transoesophageal echocardiogram (TEE), along with a severe atrial septum aneurysm on TEE. Percutaneous PFO closure with a 37 mm Gore occluder resulted in immediate resolution of hypoxaemia and clinical improvement.