Right-to-left interatrial shunt with hypoxemia caused by a right atrial thrombus.

A right-to-left shunt in the presence of normal pulmonary artery pressure is an unusual cause of hypoxemia in an adult who has a patent foramen ovale. We report a rare case of such a shunt-the result of a right atrial thrombus that formed in a hypercoagulable patient after placement of an indwelling central venous catheter for chemotherapy. In order to ascertain the nature of the right atrial mass and to decrease the risk of systemic embolization, the thrombus was surgically removed with the patient on cardiopulmonary bypass.