Platypnea-orthodeoxia syndrome is a rare but striking clinical syndrome, usually characterized by dyspnea and hypoxemia in the upright position, which is relieved by recumbency. However, the exact prevalence remains unknown. Patent foramen ovale is most commonly associated with this syndrome. Although patent foramen ovale is a common condition, the incidence of platypnea-orthodeoxia syndrome in patients with patent foramen ovale is relatively low. Here, we report a case of a 68-year-old Chinese man with platypnea-orthodeoxia syndrome due to patent foramen ovale without pulmonary hypertension who was successfully treated with transcatheter closure. A 68-year-old Chinese man presented to the emergency department with acute-onset dyspnea and hypoxemia without significant precipitating factors. Tachycardia and tachypnea were observed after the initial assessment. Transthoracic echocardiography revealed an enlarged aortic root (42 mm), mild aortic valve regurgitation, and impaired left ventricular diastolic function. No significant additional findings were observed. The patient was subsequently admitted to the Respiratory Medicine Department for further investigation. Comprehensive clinical and laboratory reevaluations revealed postural hypoxemia and dyspnea. Arterial blood gases in the upright and supine positions were as follows: partial pressure of arterial oxygen = 33/69 mmHg, partial pressure of arterial carbon dioxide = 17/22 mmHg, pH = 7.54/7.48, HCO3− = 14.5/16.4 mmol/L, and arterial oxygen saturation = 73/95% (1 minute after stopping oxygen supplementation), suggesting a provisional diagnosis of platypnea-orthodeoxia syndrome. Further evaluation using transesophageal echocardiography identified patent foramen ovale. Agitated saline transthoracic echocardiography confirmed patent foramen ovale with an atrial septal aneurysm and a right-to-left intracardiac shunt within 3–6 cardiac cycles, establishing a diagnosis of platypnea-orthodeoxia syndrome. Percutaneous patent foramen ovale closure was successfully performed. After the procedure, no residual shunting was observed, and platypnea-orthodeoxia syndrome symptoms significantly improved. Currently, the patient is in good general condition, and no breathlessness is observed. A high index of suspicion for platypnea-orthodeoxia syndrome is recommended for elderly patients with unexplained hypoxia and shortness of breath. Identification of the underlying mechanisms of platypnea-orthodeoxia syndrome will help determine future therapeutic options. An enlarged aortic root may be the most likely cause of right-to-left shunting in patients with patent-foramen-ovale-induced platypnea-orthodeoxia syndrome. More attention should be paid to aortic root size.
Hu et al. (Thu,) studied this question.