REVERSIBLE ORTHODEOXIA AND PLATYPNEA DUE TO RIGHT-TO-LEFT INTRACARDIAC SHUNTING RELATED TO PERICARDIAL-EFFUSION

A patient developed platypnea and orthodeoxia 2 weeks after coronary artery bypass graft surgery. On room air, arterial PaO2 was 45 mm Hg with the patient seated and 54 mm Hg with the patient supine. When the patient breathed pure oxygen, the PaO2- values were 79 mm Hg (seated) and 170 mm Hg (supine). Echocardiographic and computed tomographic studies showed a loculated pericardial effusion that compressed the right heart chambers. A right-to-left shunt was confirmed by doppler and contrast echocardiography. Cardiac catheterization showed near-normal cardiac and pulmonary vascular pressures. The effusion and the shunt resolved in response to corticosteroid therapy. We believe that the right-to-left shunt, which worsened with the patient in the upright posture, was caused by directed flow from the inferior vena cava toward to the left atrium through a patient foramen ovale, as the result of a pericardial effusion.