Dear Sirs,
We thank Walker and colleagues for their interesting report of a 75-year-old man with platypnoea-orthodeoxia syndrome (POS) related to a large patent foramen ovale (PFO) with preferential shunting. The patient was under surveillance for aortic root dilatation (sinus of Valsalva 41 mm on presentation).1 We would like to further elaborate on, and highlight, the strong relationship between interatrial shunt-associated POS and aortic root pathology.
In 2005, Eicher et al. retrospectively evaluated a series of 19 patients with POS due to intracardiac shunt (18 PFO, one ostium secundum defect) and found aortic root dilation in 12 of the 19 patients (63%).2 In 2007, a prospective echocardiographic study of 72 patients by Bertaux et al. described changes in geometry and mobility of the atrial septum in the presence of aortic root aneurysm. Within this cohort, 19 patients (26%) were identified with PFO. The degree of shunting was significantly associated with reduced size and increased mobility of the atrial septum and larger aortic root.3 In 2012, Rodrigues et al. analysed 188 described cases of intracardiac and extracardiac POS in the literature, and observed intracardiac shunting (most commonly PFO) as an overall cause in 24%, which was closely associated with aortic root dilatation, aneurysm or distortion.4 In 2022, Othman et al. identified 14 patients with POS associated with a highly mobile atrial septum and gaping PFO. Notable associated anatomical features were shortened distance between the aortic root and posterior atrial wall (16 ± 2 mm) compared with expected normal values (>26 mm) and ascending aortic root dilatation (37 ± 6 mm, 20 ± 5 mm/m2) resulting in aortic arch curvature. This was published in The Journal of the American Heart Association,5 and we include dimensions so that Walker et al. might respond with comparative values in their patient.1 In 2024, Farooq et al. reviewed 191 published case reports of POS secondary to intracardiac shunts. In 98 cases (51%) there was evidence of concomitant aortic root pathology. In 69 of the remaining 93 case reports (74%), there was no mention of the nature or dimensions of the aortic root, suggesting that aortic root pathology is under-reported.6
In summary, there is a small but growing body of evidence linking POS and right-to-left interatrial communication (most commonly PFO) to aortic root enlargement. Our understanding of the anatomy and pathophysiology is that the aortic root increases in size in the upright position because of gravity. Aortic root dilatation shortens the distance between the aortic root and the posterior atrial wall, resulting in aortic root wedging. The shorter the distance, the deeper the wedging into the base of the heart. This leads to compression of the right atrium and reduction of the septal area while increasing septal mobility. Aortic root enlargement also tilts the inferior vena cava (IVC) towards the plane of the atrial septum. When the patient is upright, the atrial septum is further aligned with the highest inflow from the IVC. The floppy, billowing atrial septum acts as a ‘spinnaker’,2 and the PFO gapes open, allowing venous inflow from the IVC to course directly across the PFO and bypass the pulmonary circuit.
Patients with incidental findings of aortic root pathology and unexplained hypoxaemia should be evaluated for POS and then interatrial shunts should be excluded. Transoesophageal echocardiography is the primary diagnostic tool to determine the anatomical relationship between the aortic root and the atrial septum. It is important to recognise POS because it is a debilitating condition, which is readily reversed by percutaneous shunt occlusion.
Amit K J Mandal
Consultant Physician in Perioperative and Cardiovascular Medicine
([email protected])
Piotr Szawarski
Consultant in Anaesthesia and Intensive Care Medicine
Constantinos G Missouris
Consultant Physician and Professor of Clinical Cardiology, University of Nicosia Medical School, Nicosia, Cyprus
Wexham Park Hospital, Frimley Health NHS Foundation Trust
Conflicts of interest
None declared.
Funding
None.
References
1. Walker MJ, Paranthaman GS, Jamil H. Platypnea-orthodeoxia syndrome – a rare presentation and diagnostic challenge. Br J Cardiol 2025;32(3). https://doi.org/10.5837/bjc.2025.037
2. Eicher JC, Bonniaud P, Baudouin N et al. Hypoxaemia associated with an enlarged aortic root: a new syndrome? Heart 2005;91:1030–5. https://doi.org/10.1136/hrt.2003.027839
3. Bertaux G, Eicher JC, Petit A, Dobsák P, Wolf JE. Anotomic interaction between the aortic root and the atrial septum: a prospective echocardiographic study. J Am Soc Echocardiogr 2007;20:409–414. https://doi.org/10.1016/j.echo.2006.09.008
4. Rodrigues P, Palma P, Sousa-Pereira L. Platypnea-orthodeoxia syndrome in review: defining a new disease? Cardiology 2012;123:15–23. https://doi.org/10.1159/000339872
5. Othman F, Bailey B, Collins N et al. Platypnea-orthodeoxia syndrome in the setting of patent foramen ovale without pulmonary hypertension or major lung disease. J Am Heart Assoc 2022;11:e024609. https://doi.org/10.1161/JAHA.121.024609
6. Farooq O, Ghani U, Friedman H et al. Prevalence of aortic root pathologies in platypnea-orthodeoxia syndrome secondary to intra-cardiac shunts. Cardiol Res 2024;15:125–8. https://doi.org/10.14740/cr1624
