P67: Pathology Evaluation of Polymer Foam and Hydrogel Intravascular Occlusion Devices using Histology and Transmission Electron Microscopy

Abstract

Originality: Intravascular occlusion devices are an option in the occlusion of aneurysms, vascular anomalies, fistulas or tortuous vessels. The purpose of this study is to compare the vascular occlusion properties and assess overall healing of two occlusion devices: Shape Memory Medical TrelliX Embolic coil (TrelliX; test) and an approved HydroCoil device (control). Methods: TrelliX embolic coils and an approved hydrocoil device were implanted in selected vessels of 8 pigs. Vessels were explanted and processed for plastic histology. Transmission electron microscopy (TEM) was performed on representative blocks to compare the healing of the extracellular matrix. Results: At the 30-day timepoint functional occlusion was apparent in 24/30 Test vessels and 2/18 Control vessels while at the 90-days, 19/30 Test vessels and 5/18 Control vesses were occluded using 75% occlusion as the criteria for functional occlusion. In both devices, macrophages within the vessel and draining lymph nodes contain intracytoplasmic, eosinophilic particles. Vascular particles were electron dense on TEM and were intrahistiocytic, extracellular, and within rare polymorphonuclear cells in areas adjacent to polymer/biogel degeneration. The extracellular matrix was consistent with a progressive healing process between the two time points and was adjacent to the biogel/polymer and the electron dense particles. Conclusion: Overall Test and Control articles show a similar progression toward healing, with significantly more occlusion in the Test article. Changes in the polymer/biogel of both Control and Test articles is suggestive of degradation, and the eosinophilic particles are believed to be degradation biomaterial products. These degradation products were within the vessel and draining lymph node, and due to the location of these particles, within a healthy healing matrix, show no evidence of toxic or inflammatory effect.