Hypoxia due to patent foramen ovale - in the absence of pulmonary hypertension

In most patients with a patent foramen ovale, blood flows from the left atr ium to the right atrium in the absence of pulmonary hypertension. Our repor t describes a patient with a patent foramen ovale in whom flow occurred fro m the right atrium to the left atrium in the absence of pulmonary hypertens ion. We discuss hemodynamic findings and present a brief review of the pert inent medical literature regarding this phenomenon. We also discuss the rol e of transesophageal echocardiography in the diagnosis of this condition an d in the elucidation of the underlying mechanisms, and we suggest several m echanisms that may explain the occurrence of this phenomenon in our patient .