Platypnea-Orthodeoxia Syndrome: Diagnostic Challenge and the Importance of Heightened Clinical Suspicion

Abstract

P latypnea-orthodeoxia syndrome (POS) is an uncommon condition of positional dyspnea (platypnea) and hypoxemia (orthodeoxia). The symptoms occur when the patient is upright and resolve quickly with recumbency. These findings are the opposite of those typically seen in cases of advanced heart failure and can pose a diagnostic dilemma.Even though POS was first described in the late 1940s, 1 the pathophysiologic triggers of orthodeoxia and platypnea are still not completely understood. It appears that both a functional component and an anatomic component are required.2 The syndrome has been associated with cardiac, pulmonary, abdominal, and vascular disease (functional component) in conjunction with a shunt (anatomic component). 2 The most frequently described cause is right-to-left interatrial shunting from a patent foramen ovale (PFO) or an atrial septal defect (ASD) in the presence of pulmonary hypertension.3 Positional variation in the degree of shunting in these situations remains incompletely understood. It is believed that the upright position changes or stretches the conformation of the interatrial communication, increasing the proportion of blood flow from the inferior vena cava through the defect and into the left atrium. 3 We report our experience in treating a patient who presented with POS in the absence of substantial pulmonary hypertension. Case ReportIn September 2013, an 83-year-old woman with a history of paroxysmal atrial fibrillation was admitted to the hospital after several weeks of progressive positional dyspnea that worsened with standing and improved with lying supine. On admission, the patient's pulse oximetry on room air was 96% while supine and 81% while standing. Physical examination was noteworthy for marked kyphoscoliosis. Computed tomographic evaluation for lung disease revealed a tortuous thoracic aorta with otherwise normal lung parenchyma. The patient's arterial blood gases on room air showed a significant drop in arterial oxygen tension upon postural change (from lying down to standing), confirming our suspicion of POS (Table I).A transthoracic echocardiogram revealed normal pulmonary artery pressure, with an atrial bidirectional shunt. A transesophageal echocardiogram revealed an ASD of moderate size (area, 2.2 cm 2 ) (Fig. 1), together with bidirectional shunting while the patient was supine and sedated.

Platypnea-Orthodeoxia Syndrome: A Rare and Treatable Cause of Positional Dyspnea

“…For our patient, the hypoxemia and dyspnea both improved on lying down. The hyperoxia test is performed wherein 100% oxygen is applied and the patient's partial pressure of oxygen (PaO 2 ) is measured in the supine and upright positions [1]. As mentioned earlier, our patient's oxygen saturation did not improve upon performing a hyperoxia test.…”

“…Orthodeoxia means low oxygen saturation in the upright posture and improvement when lying down. Platypnea is dyspnea in an upright position, which improves with recumbency [1]. It is an uncommon and often overlooked cause of dyspnea.…”

POJ Clinical Case Reports | Volume 1- Issue 1 – 2018

“…The pathophysiology of POS depends on the underlying etiology. Among patients with an intra-cardiac shunt, the upright position leads to a marked displacement of the interatrial septum and atrial septal defect causing preferential flow through the septal deformation magnifying the amount of deoxygenated blood that goes to the left sided circulation [3].…”

Patent Foramen Ovale Closure for Stroke Prevention and Other Disorders

“…The PFO was closed surgically and the patient's symptoms quickly resolved 39. Several other case reports indicate successful correction of the hypoxemia and symptoms after PFO closure 38, 40, 41. Mojadidi et al prospectively studied 683 patients with PFO‐associated conditions, of which 17 (2.5%) had POS and had elected to close their PFO.…”

“…Symptoms of POS are exacerbated during the upright position, but improve when recumbent 38. Although the presence of a right‐to‐left shunt through a PFO is the suspected mechanism, hypoxemia can also be caused by pulmonary shunting or ventilation‐perfusion mismatch.…”