[Posture-dependent refractory hypoxemia].

Patent foramen ovate is a common finding in the general population. However, interatrial right to left shunt causing severe hypoxemia in the absence of pulmonary hypertension is a rare finding. The authors describe two such patients suffering from severe hypoxemia refractory to oxygen supplementation. The first, a 57-year-old mate, developed severe hypoxemia several months after right pneumonectomy. The second patient, an 83 year old lady was found with severe hypoxemia after an unrelated fall and the degree of hypoxemia was posture related. Regular transthoracic Doppler echocardiography did not explain the hypoxemia in either patient. One hundred percent oxygen breathing test suggested large right to Left anatomic shunt in both patients. Doppler echocardiography with intravenous agitated saline injection demonstrated the existence of interatrial right to left blood shunting in both patients in the absence of elevated systolic pulmonary artery pressure. Both patients underwent right heart catheterization. Pulmonary arterial hypertension was ruled out and the interatrial shunt was successfully occluded percutaneously by an Amplatzer device. In both patients, hypoxemia resolved immediately after the occlusion of the interatrial shunt and their quality of life improved remarkably. In cases of unexplained refractory hypoxemia, in the absence of acute lung disease, and especially if related to upright posture, one should consider platypnea-orthodeoxia syndrome and its most common cause, a right to left interatrial shunt. This can nowadays be successfully treated percutaneously.