Abstract 13710: Cardiac Platypnea-Orthodeoxia Syndrome: How the Stars Aligned

Case description: A 79-year-old man with recurrent falls, dyslipidemia and recent exercise intolerance presented after a fall. He was putting on shoes, lost his balance and fell. There was no pre-syncope, syncope, dyspnea, chest pain, palpitations or dizziness. On admission, vital signs were normal except oxygen saturation (O2 sat) 79% on room air (and no improvement with supplemental O2). An arterial blood gas (ABG) revealed partial pressure of oxygen 42 mmHg with oxygen saturation 80%. He had lower thoracic spine tenderness, normal respiratory and cardiac exam. CT head showed no acute intracranial abnormalities. CTA chest had no pulmonary embolism, arterio-venous malformations or parenchymal lung disease. There was a thoracic aorta aneurysm (4.5cm at aortic root and 5.1cm at posterior arch). Subsequently, O2 sat was 92% supine and 79% standing. He also had a compression fracture of T12 and spinal asymmetry. A transesophageal echocardiogram (TEE) showed an aneurysmal, hypermobile interatrial septum with early right to left shunt with agitated saline due to a large patent foramen ovale (PFO). Right heart catheterization revealed no pulmonary hypertension and confirmed a step down from the pulmonary vein to left atrium (delta O2 sat 6%). A 30mm Gore Cardioform occluder was used to close the defect and immediately supplemental oxygen was removed, and O2 sat on room air was 95%. Follow up echocardiogram showed no residual shunt and exercise intolerance resolved.

Discussion: Unexplained positional hypoxemia raised our suspicion for cardiac POS. Hypoxemia is caused by right to left shunting via the PFO, exacerbated by the thoracic aortic aneurysm and spinal changes such as the T12 fracture and spinal asymmetry. Going from being recumbent to erect there is stretching of the atria causing his PFO to enlarge, increasing the shunt. Additionally, the dilated thoracic aorta exerts mechanical pressure on the right atrium (RA) and interatrial septum, increasing PFO patency and augmenting flow from the inferior vena cava through the PFO. The spinal abnormality may cause more aortic distortion and exert forces on the RA, exacerbating shunting. Percutaneous PFO closure is the treatment of choice with closure immediately leading to significant improvement of hypoxemia.