A functionally patent foramen ovale can create a relevant right-to-left shunt during massive pulmonary embolism. This associated feature, although maintaining adequate cardiac output, may explain both the paradoxic embolism and the uneffectiveness of peripherally administered drugs. This case demonstrates the potential of transesophageal echocardiography in monitoring the hemodynamic findings of such patients and, consequently, the effectiveness of thrombolytic treatment.