Platypnea-Orthodeoxia Syndrome Due to Atrial Septal Defect with Congenital Variation in the Position of the Atrial Septum and Combined Thoracic Deformities in a Young Man

doi:10.21203/rs.3.rs-3893279/v1

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Case Report

Platypnea-Orthodeoxia Syndrome Due to Atrial Septal Defect with Congenital Variation in the Position of the Atrial Septum and Combined Thoracic Deformities in a Young Man

https://doi.org/10.21203/rs.3.rs-3893279/v1

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Platypnea-orthodeoxia syndrome (POS) is a rare and complicated clinical entity with low recognition rate. The mechanisms of POS are broadly divided into intracardiac and intrapulmonary, while the detailed pathogenesis is less understood. Here we reported a POS case with atrial septal defect with congenital horizontal position of the atrial septum and combined thoracic deformities in a young man with normal right atrial pressure. This case was useful for understanding the detailed pathogenesis of POS.

Platynea-orthodeoxia syndrome

Atrial septal defect

Thoracic deformities

Intracardia shunt

Platypnea-orthodeoxia syndrome (POS) is a rare clinical entity that causes dyspnea and arterial desaturation in the upright or sitting position, and their pathogenesis is very complicated. The phenomenon was first reported in 1949 by Burchell et al. in a patient with post-traumatic intrathoracic arteriovenous shunt^[1]. The terms ‘platypnea’ and ‘orthodeoxia’ were proposed by Altman et al. and Robin et al in 1969 and 1978 respectively^{[2, 3]}. This syndrome is commonly underdiagnosed in clinical practice. We herein report a case diagnosed with Agitated saline contrast echocardiography (ASCE) and Computed tomography, which was useful for understanding the detailed pathogenesis of POS.

We presented a case of a 41-year-old man admitted to our hospital for further evaluation of postural dyspnea and desaturation. His height was 140cm and his weight was 59kg. He presented with pulse oxygen saturation (SpO2) of 90% in the supine and 83% in the upright position. Accordingly, Platypnea-Orthodeoxia Syndrome (POS) was suspected. He had congenital achondroplasia complicated by bow legs and pectus excavatum. The electrocardiogram showed sinus rhythm with no signs of ischemia, rhythm disorders, or conduction disorders, except for clockwise rotation. Additionally, pulmonary function tests and pulmonary perfusion imaging yielded nearly normal results.

Agitated saline contrast echocardiography (ASCE) was performed via the median vein of the left elbow before the operation and via the right lower extremity vein during the operation, more than 100 microvesicle echoes were seen in the left heart during one cardiac cycle (Fig. 1A). Transthoracic echocardiography implicated a 12mm atrial septal defect (ASD) (Fig. 1B) with no tricuspid regurgitation.

Computed tomography of the pulmonary artery (CTPA) ruled out lung parenchymal disease, obvious pulmonary embolism, and pulmonary arteriovenous malformation. However, it did reveal overly cardiac dislocation to the left thorax which led to right heart compression by the rib, sternum, and spine (Fig. 2A). Additionally, Sagittal reconstruction of CTPA showed a depressed sternum (pectus excavatum) and straight dorsal spine (Fig. 2B), which may also contribute partially to right heart compression. The left atrium and right atrium were arranged up and down with the atrial septum in the horizontal position (Fig. 2C), as confirmed by the orientation of the occluder (Fig. 2D). These factors might lead the blood flowing from the superior vena cava (SVC) and inferior vena cava (IVC) via ASD to the left atrium (Fig. 2E-F).

Right heart catheterization ruled out pulmonary hypertension. The right atrial pressure (RAP) was 4mmHg, mean pulmonary artery pressure was 10 mmHg, and the pulmonary vascular resistance was 96.4 dyn.s.cm^− 5. In addition, the ratio of pulmonary (Qp, 4.15 L/min) over systemic (Qs, 5.46 L/min) outflows was 0.76 (< 1), indicating a right-to-left shunt as the cause of the hypoxemia.

A 28-mm Occluder (Shanghai Shape Memory Alloy Co., Ltd, China) was successfully implanted percutaneously through the right femoral venous route, resulting in SpO₂ improved to 96% in the supine position. The PO2 levels before and after the operation in the upright position were 57 mmHg and 79.3 mmHg respectively. Pulmonary artery pressure was 15/7(11) mmHg before closure, and 15/7(10) mmHg after closure. The follow-up ultrasound showed no residual shunt, pericardial effusion, or postprocedure complications. The patient was discharged from the hospital the next day.

Platypnea-Orthodeoxia syndrome (POS) is characterized by dyspnea and arterial desaturation when a patient changes from a supine to an upright position. Since the first POS reported, more than 200 cases have been described. Both intracardiac and intrapulmonary mechanisms are involved in the pathophysiology of POS, and the intracardiac mechanism is involved in more than 80% cases. As to intracardia shunts some patients have elevated RAP, while others with normal RAP have isolated or coexisted aortic, spinal, or other intracardiac changes^[4].

In this case, the ASCE revealed that part of the venous blood from SVC and IVC flowed via ASD to the left atrium. The RAP was normal, and it was accompanied by the horizontal position of the atrial septum and combined thoracic deformities, which could contribute to the symptom.

Surgical and percutaneous occlusion of the primary defect are currently considered the definitive treatments to deal with intracardiac shunts. Percutaneous occlusion is preferred due to its faster post-procedural recovery and lower cost, with symptoms relieved in 95% of cases^[4]. In our case, the trans-catheter technique was performed, and the occluder was successfully anchored to the atrial septum with subsequent improvement in SpO2 and no complications.

A high level of suspicion for POS is essential in patients presenting with dyspnea, given its subtle and positional nature. POS mechanisms involve cardiac or non-cardiac shunts. ASCE is a simple and practical method in the diagnosis of POS. Appropriate interventions are aimed at correcting the cause and could be potentially curative.

POS

Platypnea-orthodeoxia syndrome

ASCE

Agitated saline contrast echocardiography

SpO2

Pulse oxygen saturation

ASD

Atrial septal defect

CTPA

Computed tomography of the pulmonary artery

SVC

Superior vena cava

IVC

Inferior vena cava

RAP

Right atrial pressure

Ethics approval and consent to participate

This study was approved by the Ethics Committee of Fuwai Hospital and based on the declaration of Helsinki. Informed consent was obtained from the patient for both study participation AND publication of identifying information/images in an online open-access publication (when applicable).

Consent for publication

Not applicable.

Availability of data and materials

The datasets used and/or analysed during the current case are available from the corresponding author on reasonable request.

Competing interests

The authors declare that they have no competing interests.

Funding

No Funding

Author’s contributions

Lixing Hu, Xincao Tao and Xiaoming Zhou collected the clinical data. Lixing Hu analyzed and wrote the case. Jingjin Wang provided the ultrasound data. Xiangnan Li provided the computed tomography data. Haibo Hu was the surgeon of atrial septal defect occlusion. Changming Xiong was a major contributor in writing and reviewing the manuscript. All authors read and approved the final manuscript.

Acknowledgements

We thank Editideas (www.editideas.cn) for its linguistic assistance during the preparation of this manuscript.

Burchell HBHHJ, Wood EH. Reflex orthostatic dyspnea associated with pulmonary hypertension [J]. Am J Physiol, 1949, 159): 563–4.DOI:.
Altman MRE. Platypnea (diffuse zone I phenomenon?) [J]. N Engl J Med. 1969;281:1347–8.
Robin ELD, Horn D, Theodore J. platypnea related to orthodeoxia caused by true vascular lung shunts [J]. N Engl J Med, 1976, 294): 941–3.DOI:.
Salas-Pacheco JL. [Mechanisms of platypnea-orthodeoxia syndrome] [J]. Arch Cardiol Mex. 2022;92(2):274–82. 10.24875/acm.21000171.

No competing interests reported.

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Platypnea-Orthodeoxia Syndrome Due to Atrial Septal Defect with Congenital Variation in the Position of the Atrial Septum and Combined Thoracic Deformities in a Young Man

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