Platypnoea-Orthodeoxia Syndrome as an Uncommon Cause of Dyspnoea: a Literature Review

A patient with unexplained hypoxemia after a fall diagnosed with platypnea orthodeoxia syndrome: approaches to resolving discrepancies between level of hypoxemia and clinical presentation

PURPOSE

Platypnea orthodeoxia syndrome (POS) is a rare cause of hypoxemia. Diagnosis of POS is challenging, requiring a high index of clinical suspicion, special investigations, and collaboration with multiple specialists.

CLINICAL FEATURES

We describe an 86-yr-old male who presented to the emergency department with hip pain after a witnessed fall. He was noted to be hypoxemic at presentation with a peripheral oxygen saturation (SpO2) of 84% on room air, with an inadequate increase in oxygenation after administration of a fractional concentration of inspired oxygen (FIO2) of 1.00. A chest radiograph, computed tomography pulmonary angiogram, and Doppler ultrasound of the liver were unremarkable. In the supine position with an FIO2 of 0.65, his SpO2 and arterial partial pressure of oxygen (PaO2) (96% and 74 mm Hg, respectively) increased significantly relative to the seated position (84% and 50 mm Hg, respectively). Contrast transthoracic echocardiography (TTE) showed a large patent foramen ovale (PFO) with right-to-left shunt. Transthoracic echocardiography showed rotation of the patient's heart, enabling direct alignment of the inferior vena cava with the PFO, creating a large anatomical right-to-left shunt in the seated position. Right heart catheterization confirmed a large PFO with normal right-sided heart pressures. He was treated with a septal occlusion and his SpO2 in the seated position improved immediately. The patient was discharged home without requiring supplemental oxygen.

CONCLUSIONS

Platypnea orthodeoxia syndrome is a rare presentation of hypoxemia. Positional changes in oxygenation are the cardinal feature of POS. Discordance between lung imaging and the severity of hypoxemia should prompt investigation for an intracardiac shunt, which can occur in POS even in the absence of increased right-sided heart pressures. Either contrast TTE or transesophageal echocardiography is necessary to make this diagnosis.

Two women with unexplained dyspnoea: removing the blame game from the lungs

Hypoxaemia due to right-to-left atrial shunt with normal pressures in the right heart cavities represents an underdiagnosed condition. A systematic approach to hypoxaemic respiratory failure based on pathophysiology can lead to an accurate diagnosis. https://bit.ly/4bTP8fJ.

Prevalence of Aortic Root Pathologies in Platypnea-Orthodeoxia Syndrome Secondary to Intra-Cardiac Shunts

Background

Atrial septal defects can allow right to left shunting of venous blood which presents clinically as platypnea-orthodeoxia syndrome. It is believed that concomitant presence of aortic root pathologies increases the likelihood of shunting.

Methods

The study included a review of 510 articles listed in PubMed of patients with platypnea-orthodeoxia syndrome. Case reports of patients with extra-cardiac etiologies of platypnea-orthodeoxia were excluded.

Results

We reviewed 191 case reports, and 98 cases (51.3%) had evidence of concomitant aortic root pathology. Furthermore, of the remaining 93 case reports, 69 ones excluded any mention of the nature of the aortic root altogether, further suggesting that this is an underreported number.

Conclusions

There is a high prevalence of aortic root pathologies in patients with platypnea-orthodeoxia syndrome secondary to intra-cardiac shunts. In patients with unexplained hypoxemia and incidental finding of aortic root pathology, it may be worthwhile to obtain postural oxygen saturation measurements to exclude intra-cardiac shunts as the potential cause.