Technical feasibility and histopathologic studies of ethylene vinyl copolymer (EVAL) using a swine endovascular embolization model.

PURPOSE To study the safety, technical efficacy, and histopathology of the ethylene vinyl alcohol copolymer (EVAL) embolic mixture in an animal model. METHODS Microcatheterization of the rete was performed in 29 swine. The clinical, angiographic, and histopathologic consequences of superselective injection of the two principal embolic mixture components (EVAL and dimethyl sulfoxide [DMSO]) were evaluated. Necropsy and standard histologic preparation were used for pathologic analysis. RESULTS Significant technical difficulties and adverse outcomes occurred. The EVAL mixture was difficult to see under fluoroscopy and prematurely polymerized during one embolization, resulting in catheter occlusion. However, polymerized EVAL did not adhere to the catheter. DMSO damaged the plastic hubs of the microcatheters. Infusions of DMSO always caused immediate, moderate to severe vasospasm and frequently caused either subarachnoid hemorrhage or stroke. Histopathologic findings of both DMSO and DMSO plus EVAL were similar, producing variable endothelial denuding, thrombosis, and disruption of internal elastic lamina in the acute stage. An intense, mixed inflammatory response, organized thrombus, and transmural necrosis with extravasation were seen in the subacute and chronic stages. CONCLUSIONS Despite having some desirable features as an embolic agent, significant problems were encountered with EVAL; the most important of which is that one of the principal components of the embolic mixture, DMSO, seems to be very angiotoxic.