Occlusion of Experimentally Created Fusiform Aneurysms with Porous Metallic Stents

Angiographic findings of a fusiform carotid artery aneurysm.

A, Eight weeks after stent placement there is near-complete ablation of the aneurysmal lumen (arrows).

B, The Wallstent within the carotid artery.

C, The control fusiform aneurysm (arrows) and the carotid artery remain widely patent throughout the 8-week period of observation.

Gross pathologic examination.

A, Gross end-block specimen of control aneurysm shows the walls remain widely dilated.

B, The outer walls of the stented aneurysm have contracted along the length of the stent, producing a narrower profile of the carotid artery as compared with the profile of the control aneurysm.

C, Control aneurysm, cross section. Section 3 shows the markedly dilated lumen of the fusiform aneurysm.

D, Stented aneurysm. Section 4 is through the center of the fusiform aneurysm. Note the contraction of the outer walls of the aneurysm along the stent, again producing a narrower profile of the carotid artery and aneurysm as compared with the control aneurysm. The lumen between the stent and outer wall of the aneurysm is filled with white, organized thrombus.

E, Longitudinal section. All stents were embedded in a glistening, translucent neointima. The stented aneurysms appear solid except for small channels, which connect the lumens of the carotid arteries with those of the aneurysms (arrows).

Histopathologic findings.

A, Mason's trichrome stain on stented aneurysm shows the aneurysmal lumen is nearly completely filled in with organized fibrous connective tissue (curved arrows). The stent wires are surrounded by neointima (straight arrows).

B, Mason's trichrome stain on control aneurysm in cross section shows markedly distended thin wall of the aneurysm.

C and D, Trichrome stain on stented aneurysm in longitudinal section shows a small, patent endothelial-lined channel at one margin, connecting the carotid lumen with the aneurysmal lumen (arrow). These small channels were seen in all aneurysmal specimens. The remainder of the aneurysmal lumens were filled in by fibrous connective tissue (organized thrombus). Within the neointima surrounding the stent wires there was mild inflammatory cell infiltration (macrophages). Many macrophages contained blood pigment (resolving thrombus).

E, Magnified cross-sectional view of aneurysmal lumen with Mason's trichrome stain. Fibrin and collagen stain blue. Dark blue represents more mature fibrin and collagen. Mature fibrous elements and collagen (dark blue) were noted near the periphery of the aneurysmal wall (thin arrows); less mature fibrous elements (light blue) lie near the central lumen of the aneurysm (thick arrows), suggesting that thrombus organization begins along the outer wall and progresses in a centripetal fashion toward the central lumen of the aneurysm.

F, Verhoeff-van Gieson elastic stain shows heavily vascularized organized thrombus (arrows).