|LETTER TO THE EDITOR
|Year : 2019 | Volume
| Issue : 3 | Page : 225-226
Platypnea–Orthodeoxia syndrome: Revisiting the enigmatical hypoxemia!
Rohan Magoon, Neeti Makhija, Subhajit Sahoo, Devishree Das
Department of Cardiac Anaesthesia, Cardiothoracic Centre, CNC, All India Institute of Medical Sciences, New Delhi, India
|Date of Submission||29-Jul-2019|
|Date of Acceptance||02-Sep-2019|
|Date of Web Publication||20-Dec-2019|
Room No. 9, 7th Floor, Department of Cardiac Anaesthesia, Cardiothoracic Centre, All India Institute of Medical Sciences, Ansari Nagar, New Delhi - 110 029
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Magoon R, Makhija N, Sahoo S, Das D. Platypnea–Orthodeoxia syndrome: Revisiting the enigmatical hypoxemia!. J Pract Cardiovasc Sci 2019;5:225-6
|How to cite this URL:|
Magoon R, Makhija N, Sahoo S, Das D. Platypnea–Orthodeoxia syndrome: Revisiting the enigmatical hypoxemia!. J Pract Cardiovasc Sci [serial online] 2019 [cited 2020 Jan 25];5:225-6. Available from: http://www.j-pcs.org/text.asp?2019/5/3/225/273739
Platypnea–orthodeoxia represents an uncommon syndrome that can often be difficult to articulate, albeit carries plenty of information. It is characterized by positional dyspnea (platypnea) and hypoxemia (orthodeoxia) with pronounced symptomatology in the upright posture, and a tendency to resolve with recumbency. This clinical pattern is peculiarly contrasting from the usual presentation of a decompensated congestive cardiac failure, posing a diagnostic conundrum.
Ever since the first description of platypnea–orthodeoxia syndrome (POS) in the 1940s, the pathophysiological understanding of the syndrome remained clouded for a relatively long period. It is now perceived that a co-existence of an anatomical and a functional component is the basis of manifestation. The anatomical component is heralded by the interatrial communication (IAC) in the form of a patent foramen ovale (PFO), an atrial septal defect, or an atrial septal aneurysm. Physiologically speaking, the IAC should result in a left-to-right (L-R) shunting of blood considering the higher pressure in the left atrium (LA) compared to the right atrial (RA) pressure. An R-L interatrial shunting can materialize in the presence of pulmonary hypertension. However, the R-L shunt mechanism remains elusive in lack of a RA-LA pressure gradient. This has been explained by the functional component of POS which induces a preferential streaming of the shunt flow from RA-LA, in the upright posture.
The functional component can emanate as a consequence of a range of intracardiac or extracardiac conditions. The most conspicuous description of a cardiac POS is provided by stretching of the IAC on standing upright, accounting for the redirection of the inferior vena cava blood to the LA through the IAC, which becomes marked in the presence of a prominent Eustachian valve More Details. Some authors propose that the abnormal angulation of the atrial septum could account for the vortex of caval venous blood flow toward the LA. Intrapulmonary shunts as in hepatopulmonary syndrome (HPS) and the diseases leading to augmented ventilation–perfusion (V/Q) mismatch can also present as POS [Table 1].
An elevated risk of paradoxical embolism and other concerns such as migraine, cryptogenic headache, or cerebrovascular accidents prompt an early diagnosis of POS, which is largely based on a high index of clinical suspicion. An orthostatic desaturation is evident on blood gas analysis, with a pO2<60 mmHg in the upright position which normalizes on lying down. An early appearance of contrast (within first three beats) in LA on contrast-enhanced echocardiography following RA opacification signifies a cardiac POS, whereas a delayed appearance (3–6 beats) of LA contrast signals an extracardiac cause of POS such as HPS. The sensitivity of the test is accentuated by observing for the contrast at the termination of a Valsalva maneuver. V/Q study, scintigraphy with macro-aggregated albumin, and pulmonary arteriography also aid in characterizing the underlying cause. The R-L shunting can be screened and quantified with the transcranial Doppler studies, and percutaneous transcatheter device closure of the IAC can alleviate the potential suffering attributable to POS.
To conclude, POS is a rare disorder which should be considered in the scenario of orthodeoxia, no other obvious pathology, leading to dyspnea and should be worked up for the underlying mechanistic cause such as PFO. However, the discrepancy between the incidence of PFO (nearly 20%) and a rather rare occurrence of POS clearly elucidates the additional complexities in conjunction with a PFO that results in the classical presentation of POS.
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