Right ventricular (RV) infarction is a well-recognized complication of acute inferior myocardial infarction. Rightto-Left shunt through a patent foramen ovale (PFO) is an unusual complication of acute RV myocardial infarction that can result in the development of severe hypoxemia. However, the diagnosis may not be easy without high index of suspicion and echocardiography combined with an echocardiographic contrast (agitated saline) is useful diagnostic imaging modality in this regard. We report a case of acute inferior myocardial infarction and RV infarction associated with unexplained hypoxemia. Contrast echocardiography detected a significant right to left shunt through patent foramen ovale, which considered as a cause of hypoxemia in this patient.