Hypoxia Due to a Large Right to Left Interatrial Shunt with Normal Right-Sided Filling Pressures in the Setting of a Separation between the Septum Primum and Secundum: A Case Report.

Hypoxia secondary to right to left interatrial shunting in the setting of normal right-sided filling pressure is an uncommon clinical presentation. We present a case of persistent hypoxia irrespective of body position in a patient with a wide separation between the septum primum and secundum, creating a tunnel channeling flow from the right to the left atrium. Hypoxia resolved instantly following closure of the defect with an Amplatzer occluder under intracardiac echocardiography guidance. Although platypnea-orthodeoxia leads to hypoxia in the setting of normal right-sided filling pressures, the finding of a coexisting wide gap between the septum primum and secundum is likely to have worsened the hypoxia making it severe irrespective of body position. Closure of the interatrial septal defect led to immediate and sustained resolution of the hypoxia.