676 Platypnea-Orthodeoxia Syndrome: Key Pathogenetic Role of Patent Foramen Ovale (PFO) and Dramatic Response to PFO Closure

Abstract

PFO-associated platypnea-orthodeoxia syndrome (POS) is characterised by dyspnoea and hypoxaemia when upright. The pathogenesis is thought to involve an increase in right atrial pressure or change in degree of right to left shunting with upright posture. We sought to characterise patients with POS related to PFO without pulmonary hypertension. We retrospectively reviewed databases at three tertiary referral hospitals in New South Wales, Australia from 2000 to 2019. Fourteen patients with a mean age of 69±14 years of age had a PFO with wide tunnel separation. Median NYHA Class was II and 7 inpatients had been confined to bed (from postural symptoms). It was 30±33 days from onset of POS to diagnosis. Baseline oxygen saturations supine were 93±5% and 84±6% upright. 2 patients had a minor congenital heart Platypnea-orthodeoxia Syndromedefect and 4 had mild parenchymal lung disease with preserved lung function. The mean aortic root diameter was 37±6mm and distance between aortic root and posterior atrial wall was 16±2mm. POS was preceded by surgery in 5 patients and 1 patient had mild pneumonia. Successful closure of the PFO using an Amplatzer device was performed in 11 of 14 patients. Post-closure, NYHA Class improved by 2±0.9 (p<0.001, n=11) and supine oxygen saturations increased by 13±8% (p<0.001, n=10). POS is a debilitating condition, curable by PFO closure. Anatomical distortion of the atrial septum related to a dilated aortic root or shortening of the distance between the aortic root and posterior atrial wall may contribute to the syndrome.