Entrapment of a floating thrombus in the right atrium by persistent Chiari's network: a barrier to massive pulmonary embolism.

Syncope may be a manifestation of pulmonary embolism. Occlusion of a pulmonary artery with cardiac output drop, sometimes resulting in cardiac arrest, is the main underlying mechanism. In this letter we describe the case of a patient in which the persistence of a long remnant of the embryonal Chiari's network could have worked as an anatomic barrier preventing massive pulmonary embolism and cardiac arrest.