In-vivo short- and long-term evaluation of the interaction material-blood.

Through an innovative electron microscopy technique, thrombi and fibrotic tissue taken from 14 explanted vena cava filters were observed. Twelve cases showed the presence of micro-and nano-sized inorganic, non biodegradable nor biocompatible particles which did not belong to the metal the device was made of and which could be the sole cause or, more likely, a pre-existing cause for thrombosis. In two cases, those debris activated immunological reactions typical of a foreign body. The presence of inorganic particles in the blood was never detected before and their effects on human health are hardly known. Their thrombogenicity should be added to the Virchow's Triad as a fourth factor and could be the explanation to many of the cases of pulmonary embolism where no thrombotic focus could be demonstrated.