Abstract Introduction Platypnea–orthodeoxia syndrome (POS) is characterized by paradoxical positional dyspnea, which worsens in the upright position and improves when lying down. Percutaneous closure of a patent foramen ovale (PFO) is a straightforward procedure for correcting POS and refractory hypoxemia. This study aimed to 1) evaluate the effectiveness of percutaneous PFO closure in terms of improving dyspnea and oxygenation 2) to identify factors associated with procedural failure and 3) to analyze the impact of a residual post-procedural shunt. Materials and Methods We conducted a monocentric observational registry at University Hospital of Strasbourg between June 2010 and February 2024. The primary composite endpoint was defined by improvement in oxygenation (complete withdrawal of supplemental oxygen, ≥ 10% increase in oxygen saturation SpO₂, 15 mmHg rise in PaO₂, or SpO₂ 93% on room air) and/or improvement in dyspnea (at least one class improvement in NYHA or mMRC scores). Secondary endpoints included procedure-related complications (procedural issues, mortality, stroke) and the persistence of a significant residual shunt. Results Among 264 patients who underwent PFO closure, 50 were treated for POS or severe hypoxemia. Mean age was 73 and 44% of patients were women. An improvement in both oxygenation and dyspnea was observed in 36 patients (72%). The main independent predictor of procedural failure was the presence of a significant residual shunt (HR 14.2; 95% CI 1.31–50; p = 0.02). At follow-up, 6 patients (12%) presented a significant residual shunt. The only independent predictor of this residual shunt was the distance between the device’s right and left discs ( 5.05 mm) (HR 8.90; 95% CI 1.16–68.35; p = 0.03). Procedure-related complications were very rare, confirming the safety of percutaneous PFO closure. Conclusion In patients with POS or severe hypoxemia, percutaneous PFO closure effectively improves dyspnea and oxygenation in approximately two-thirds of cases. A persistent significant residual shunt was identified as a poor prognostic factor and was associated with the distance between the two discs of the closure device. These findings, reported for the first time in this condition, underscore the importance of careful patient selection and thorough anatomical assessment to optimize clinical outcomes.Box Plot of saturation in O2 Multivariate regression
Ndiaye et al. (Sat,) studied this question.