Unmasking platypnoea-orthodeoxia syndrome: a systematic review of the pathophysiology, clinical spectrum and outcomes of percutaneous intracardiac shunt closure

BACKGROUND: Platypnoea-orthodeoxia syndrome (POS) is a rare but underdiagnosed cause of positional dyspnoea and hypoxaemia. It results from right-to-left interatrial shunting through a patent foramen ovale (PFO) or atrial septal defect (ASD), often precipitated by anatomical or functional distortions. OBJECTIVES: We systematically characterised the clinical spectrum, anatomical correlates and procedural outcomes associated with percutaneous closure in patients diagnosed with intracardiac POS. METHODS: A systematic search of PubMed, Embase and MEDLINE databases was conducted. Case reports, case series and observational studies were included if they involved patients with POS with percutaneous closure of PFO/ASD. RESULTS: A total of 469 patients from 196 studies (183 case reports/series, 13 observational studies) were identified (mean age 68.3±14.1 years; 51% female). Common symptoms included orthodeoxia (95%), exertional dyspnoea (42%) and platypnoea (35%) with a median time from symptoms to diagnosis of 13 (IQR 4-26) weeks. Anatomical contributors included aortic dilation (33%), thoracic structural abnormalities/surgery (33%) and right heart disorders (15%). A mean PFO/ASD diameter of 11.5±5.2 mm and a pulmonary blood flow/systemic blood flow ratio of 0.89±0.34 was noted. Amplatzer occluders were the most used device (60% of closures). Postclosure oxygen saturation improved significantly (pre: 79.5±8.7% vs post: 94.5±5.0%). Symptomatic improvement was reported in 82% of cases, with a low procedural complication rate of 5%. CONCLUSIONS: POS remains an underdiagnosed clinical entity, where systematic evaluation for POS should be considered in patients with positional desaturation and unexplained hypoxaemia. Percutaneous closure of the interatrial shunt offers significant symptomatic and physiological benefit with a favourable safety profile. PROSPERO REGISTRATION NUMBER: CRD420250652717.