In vivo embolization of lateral wall aneurysms in canines using the liquid-to-solid gelling PPODA-QT polymer system: 6-month pilot study: Laboratory investigation

Object. Over the past 20 years, endovascular embolization has become the preferred method of treating cerebral aneurysms. While there are many embolic devices on the market, none is ideal. In this study the authors investigated the use of a liquid-to-solid gelling polymer system-that is, poly(propylene glycol) diacrylate and pentaerythritol tetrakis (3-mercaptopropionate) (PPODA-QT)-to embolize in vivo aneurysms over a 6-month period. Methods. Experimental aneurysms were created in the carotid arteries of 9 canines. Aneurysms were embolized with the polymer only (PPODA-QT, 3 dogs), filled with PPODA-QT after placement of a 'framing' platinum coil (coil + PPODA-QT, 3 dogs), or packed with platinum coils (coils only, 3 dogs). Aneurysm occlusion was angiographically monitored immediately and 6 months after embolization. After 6 months, the ostial regions of explanted aneurysms were assessed macroscopically and histologically. Results. All aneurysms showed 100% angiographic occlusion at 6 months, but turbulent blood flow was observed in 1 coils-only sample. Ostial regions of explanted coils-only aneurysms showed neointimal tissue surrounding individual coils but no continuous tissue layer over the aneurysm neck. All PPODA-QT aneurysms displayed smooth ostial surfaces, but 2 of 3 coil + PPODA-QT aneurysms showed polymer (unassociated with the coil) protruding into the vessel lumen, contributing to rough ostial surfaces. Neointimal tissue was present in PPODA-QT and coil + PPODA-QT aneurysms and covered smooth ostial surfaces more completely than in coils-only aneurysms. Conclusions. This study compared neointimal tissue overgrowth in the ostium of experimental aneurysms embolized with PPODA-QT, PPODA-QT plus a framing coil, or coils alone. The coils-only and coil + PPODA-QT groups showed rough and discontinuous ostial surfaces, which hindered neointimal tissue coverage. The PPODA-QT aneurysms consistently produced smooth ostial surfaces that facilitated more complete neointimal tissue coverage over aneurysm necks.