INTERMITTENT RIGHT-TO-LEFT SHUNT DESPITE NORMAL RIGHT ATRIAL PRESSURES

First described in 1949, platypnea-orthodeoxia syndrome is a clinically underrecognized syndrome defined by O2 desaturation in the upright position but not in the supine position. Reported causes include intracardiac shunting, pulmonary vascular shunting, ventilation-perfusion mismatch, or a