Not all unexplained hypoxia is pulmonary embolism.

Acute myocardial infarction is one of the conditions frequently managed in the emergency department. There are many complications associated with right ventricular infarction, and the incidence of right ventricular infarction associated with inferior myocardial infarction is as high as 51% based on electrocardiographic findings. We herein report the case of a 45-year-old Chinese man with inferior myocardial infarction complicated by right ventricular failure. He had hypoxaemia refractory to supplemental oxygen due to an acute right-to-left shunting through a patent foramen ovale (PFO). He underwent coronary angioplasty and closure of the PFO. It is crucial for the attending physician to consider the presence of a right-to-left shunt when there is persistent uncorrectable hypoxaemia despite maximal oxygen supplementation in the setting of right ventricular infarction, as there are clinical implications and certain clinical managing principles that should be applied.