RESUMEN
A 29-year-old woman was referred to our institute for symptomatic hypoxemia. Her dyspnea was aggravated while sitting or standing and relieved while in supine position. She did not have any pulmonary disease. Transthoracic echocardiography and heart computed tomography revealed an underestimated small atrial septal defect (ASD) with a left-to-right shunt. A cardiac catheterization was performed to evaluate pulmonary hypertension. It revealed a normal pulmonary artery pressure and a large ASD with bidirectional shunt during Valsalva maneuver by intracardiac echocardiogram. Her arterial oxygen saturation decreased from 93% while supine to 79% while at a 15degrees sitting position. Thus, the patient was diagnosed with platypnea-orthodeoxia syndrome. The ASD was successfully closed with Amplatzer(R) (St. Jude Medical) septal occluder and both platypnea and orthodeoxia were resolved immediately after the procedure.