Paradoxical embolism. An old but, paradoxically, under-estimated problem.

The theoretical model of paradoxical embolism requires the presence of four parameters, namely, arterial embolism, venous thrombus, abnormal intracardiac communication and right-to-left shunt. Many aspects, however, of this well known entity are under consideration; diagnosis is often difficult to be established and the long term efficacy of preventive measures is undefined. We comment on a case report of recurrent paradoxical embolism with popliteal vein thrombosis and patent foramen ovale, and we briefly review the literature.