Histopathologic appearance of arterial occlusions with hydrogel and polyvinyl alcohol embolic material in domestic swine

PURPOSE: This study observes the histologic changes resulting from a hydrogel embolic agent (polyacrylonitrile [PAN]) compared with polyvinyl alcohol particles (PVA) of similar size. MATERIALS AND METHODS: Hepatic and renal embolizations were performed in 13 domestic swine by selecting small (1-mm) branches utilizing a coaxial 3-F microcatheter. The hydrogel embolie agent (tantalum-loaded and plain) and PVA were delivered through microcatheters. The longest follow-up period was 8 weeks. Postmortem examination of the embolized tissues included gross examination and histologic analysis. RESULTS: Tantalum-loaded PAN particles were radiopaque and seen in groups fluoroscopically and individually with specimen radiography. Histologic studies showed similar luminal and cellular response to PVA and the hydrogel embolie agents. The arterial lesion induced by the hydrogel embolie agents led to an absence of the arterial wall locally in the area of deployment. Hydrogel embolie particles became surrounded in fibrous connective tissue with no arterial wall. PVA and porous hydrogel capsules produced an inflammatory response, resulting in less wall reorganization, and surrounding fibrous connective tissue at 8 weeks than the solid PAN particles. CONCLUSION: These hydrogel emboli create a permanent arterial occlusion by transmural arterial damage. Mechanical effects and, to a lesser degree, inflammatory changes are responsible.