Scintigraphic demonstration of a right-to-left intracardiac shunt in a patient with massive pulmonary emboli.

A case of massive pulmonary embolism resulting in marked pulmonary to systemic shunting in a patient with a previously clinically inapparent ventricular or atrial septal defect is presented. The various types of unrecognized intracardiac shunts and their prevalence in the adult population are discussed.