Platypnoea-orthodeoxia syndrome: the importance of the patient’s posture for diagnosis
- 1 Internal Medicine, Centro Hospitalar de Entre o Douro e Vouga EPE, Santa Maria da Feira, Portugal
- 2 Cardiology, Centro Hospitalar Universitário do Porto EPE, Porto, Portugal
- Correspondence to Dr Carla Pereira Fontes; carla.pfts@gmail.com
Abstract
Platypnoea-orthodeoxia syndrome (POS) is a rare condition characterised by the association of dyspnoea and arterial oxygen desaturation induced by standing and relieved by recumbency. The precise mechanism remains poorly understood, but it appears to involve both anatomical and functional components producing a significant right-to-left shunting under certain postural conditions. This syndrome is associated with either intracardiac or extracardiac aetiologies, and the diagnosis depends on high clinical suspicion. Intracardiac shunt is the most common cause of POS and can be identified through echocardiography with bubble study. We report the case of a patient with POS secondary to a paradoxical shunt through the patent foramen oval, whose definitive diagnosis was only possible with contrasted transthoracic echocardiography in the sitting and standing positions.
Background
The platypnoea-orthodeoxia syndrome (POS) is a rare clinical disorder presenting with dyspnoea (platypnoea) and hypoxemia (orthodeoxia) in standing position that improves on recumbency.
First described in 1949 by Burchell and Wood, POS was initially interpreted as a functional disability and termed ‘orthostatic cyanosis’.1 2 Thenceforth, less than 250 cases have been reported in the literature, the majority in the last decade.3 4
A paradoxical right-to-left shunting (RLS) triggered by postural changes is the underlying disorder.5–7 Among the several aetiologies that have been associated with this syndrome, cardiac conditions are the most frequent.3 8 In these cases, anatomical deformities in the form of interatrial communications, such as patent foramen ovale (PFO), atrial septal defect or fenestrated atrial septal aneurysm (ASA), allow communication between the right and left circulation. But, since pulmonary pressures are usually normal in POS, a functional/haemodynamic factor that promotes abnormal shunting of deoxygenated blood into the higher pressure systemic circulation under certain postural and loading conditions is required.8
We present a case of POS associated with PFO, in which echocardiography with dynamic postural manoeuvres in sitting and standing positions was crucial to establish the diagnosis of intracardiac RLS.
Case presentation
A 73-year-old woman with hypertension and type 2 diabetes presented to the emergency department with a 3-month history of progressive exertional dyspnoea (she was mildly dyspnoeic at rest and was almost completely unable to climb a flight of stairs without stopping). She denied orthopnoea, paroxysmal nocturnal dyspnoea, chest pain, palpitations or lower limb oedema.
About 2 weeks before the initial admission, she experienced a right lacunar stroke with complete resolution of symptoms (left inferior limb hypoesthesia), being discharged home on antiplatelet therapy. Outpatient evaluation at that time included carotid sonography with Doppler analysis, which excluded significant lesions and transthoracic echocardiography (TTE), that revealed normal chamber sizes with moderate hypertrophy of the interventricular septum and left ventricular ejection fraction of 46%; a redundant fossa ovale membrane without apparent shunt was also noted.
On admission, her physical examination was only notable for a low resting pulse oximetry saturation on room air (89%). She was afebrile and haemodynamically stable. There was no evidence of lung rales or cardiac murmur, peripheral oedema, raised jugular venous pressure or others signs of heart failure.
Investigations
An arterial blood gas test on room air revealed partial arterial oxygen pressure (PaO2) of 52 mm Hg and a partial pressure of carbon dioxide of 32 mm Hg. Laboratory studies, including haematological and biochemical analysis, were in the normal range; brain natriuretic peptide level was 18.2 pg/mL (normal <100 pg/mL). The ECG showed normal sinus rhythm with an already known complete left bundle branch block pattern and first-degree atrioventricular block. Contrast-enhanced CT ruled out pulmonary embolism, intrapulmonary vascular malformations and lung parenchymal abnormalities. In later observation, however, with the patient in the supine position, oxygen saturation was 95% and PaO2 of 74 mm Hg on room air. POS was then suspected and a TTE with intravenously administered agitated saline contrast solution was performed, but shunt was not observed. The patient was further evaluated with transoesophageal echocardiography, which showed ample bilateral movement of the interatrial septum, with no evidence of shunt; bubble study with Valsalva manoeuvre was once again negative. Right atrial pressure was low and right ventricular function was normal in both echocardiographic assessments. Considering the results, a pulmonary perfusion scintigraphy with technetium 99mTc-macroaggregated albumin was performed, demonstrating no extrapulmonary uptake, not confirming the presence of pathological RLS.
Disregarding other causes of POS and persisting suspicion of posture-dependent reversible paradoxical intracardiac shunt, the patient underwent another TTE with bubble-agitated serum study. However, her position during the procedure changed from supine (oxygen saturation of 96%) (video 1) to sitting (video 2) and standing (video 3), and solely in later postures, interatrial shunting was observed within the first three cardiac cycles; oxygen saturation simultaneously fell to 88%–92%. A large (17 mm) PFO associated with an ASA with spontaneous shunt flow from the right to left cardiac cavities was later confirmed.
Differential diagnosis
In addition to cardiac causes, POS has also been described with intrapulmonary shunting, as occurs in pulmonary arteriovenous malformations (including acquired pulmonary arteriovenous communications in patients with hepatopulmonary syndrome) and lung parenchymal diseases with severe ventilation-perfusion mismatching (Osler-Weber-Rendu disease, emphysema, interstitial lung disease or pneumonia).2 9 Certain conditions can lead to combined cardiopulmonary-related POS, such as pneumonectomy and kyphoscoliosis; and several other causes (miscellaneous) have been related with POS through unexplained mechanisms, such as amiodarone pulmonary toxicity, autonomic neuropathy, radiation-induced bronchial stenosis or traumatic bronchial rupture.5 10
In our case, there were no other explanations for the POS other than the shunt associated with cardiac defects.
Treatment
The PFO was successfully closed by percutaneous cardiac catheterisation using a 25 mm occluder device (Amplatzer) placed across the interatrial defect. A postprocedural imaging was negative for residual shunting. The patient’s dyspnoea and hypoxemia improved immediately, not requiring oxygen supplementation.
Outcome and follow-up
At the 1-month follow-up, the patient was asymptomatic and able to return to her previous daily routine.
Discussion
POS results from a position-dependent RLS of either intra or extracardiac causes. Although the precise pathophysiologic mechanisms are still not clear, one theory suggests that atrial defects may acquire a conformational change during adult life that may be stretched by gravity, causing a selective blood flow through the interatrial communication when the patient is standing, but this baffling effect is dynamic as it resolves when the patient returns to the supine position2 5 11; other hypothesis involves a temporary increase in right atrial pressure with concomitant transient reversal of the left-to-right atrial gradient, elevated pulmonary vascular resistance (chronic obstructive pulmonary disease, pneumonectomy, pulmonary embolism or hypertension), increased right-sided filling pressures to maintain cardiac output (constrictive pericarditis, pericardial effusion, cardiac tamponade, Eisenmenger syndrome) or decreased right-sided compliance (right ventricular ischaemia).2 12
Most patients reported in the literature have only one anatomic and one functional defect. In our patient, two anatomic defects were identified, PFO and ASA, the later much less common (prevalence of 2%–3% for ASA vs 25%–30% for PFO).13 14 ASA has been associated not only with the presence of PFO, as well as an increase in its size, as the distortion of the atrial septum caused by ASA contributes to the paradoxical RLS through the PFO, triggered by postural change, leading to considerable hypoxia, despite the absence of pulmonary hypertension.15
Different diagnostic modalities can be used to confirm the presence of PFO. Nevertheless, body position is particularly relevant, since it greatly affects the diagnosis of POS, as experienced by our patient. If no cardiac cause is identified, other conditions prone to cause POS should be investigated.
Definitive treatment of POS involves correction of underlying anomaly. PFO percutaneous closure has proven to be safe and effective, with low complication rates and symptomatic improvement seen in more than 95% of patients.8
Learning points
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Platypnoea-orthodeoxia syndrome (POS) should be considered in the workup of dyspnoea, and a position-dependent drop in arterial oxygen saturation is the confirmatory finding.
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A high index of suspicion is essential to recognise POS given the absence of symptoms when the patient is lying down, the usual position during routine examinations.
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Because of the positional effects on intracardiac haemodynamic, diagnostic testing should be performed using dynamic postural manoeuvres to establish the definitive diagnosis of POS.
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Awareness of this syndrome is of paramount importance, as it is potentially treatable and completely reversible.
Footnotes
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Contributors CPF was involved in drafting the article. SBF and MS were involved in revising the article critically for important intellectual content. All authors read and approved the final manuscript.
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Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
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Competing interests None declared.
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Provenance and peer review Not commissioned; externally peer reviewed.
- © BMJ Publishing Group Limited 2021. No commercial re-use. See rights and permissions. Published by BMJ.
References
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