PAIRED-COMPARISON OF VASCULAR WALL REACTIONS TO PALMAZ STENTS, STRECKER TANTALUM STENTS, AND WALLSTENTS IN CANINE ILIAC AND FEMORAL ARTERIES

Background Palmaz stents, Strecker stents, and Wallstents, all used cl inically, differ substantially in their physical characteristics, yet how differently the vascular wall reacts to them has not been demonstr ated conclusively. We therefore undertook a side-by-side comparison. M ethods and Results One stent was implanted into each canine external i liac and/or the flexing portion of the proximal femoral artery. In 9 d ogs, Palmaz stents were placed vis-h-vis Strecker stents, with follow- up of 2 and 4 months. In 7 dogs, Palmaz stents were placed vis-g-vis W allstents, with 4 months of follow-up. Angiographic midstent luminal d iameters immediately after placement and at follow-up as well as midst ent cross-sectional areas of neointima were compared for significant d ifferences. In addition, neointimal maturation, medial atrophy, and st ent-related trauma were assessed. Angiographically, all arteries remai ned open. The degree of luminal narrowing by recoil and neointima neve r reached 50% and was modest for Palmaz stents and Wallstents (P=.33) but significantly higher for Strecker stents (P<.0001 compared with Pa lmaz stents). This corresponded histologically to a significantly thic ker neointima (P=.003) over Strecker than over Palmaz stents but not b etween Palmaz stents and Wallstents (P=.18). Neointimal buildup was ge nerally more pronounced in the femoral artery segments than in the ili ac segments. Maturation of the neointima over Palmaz stents was much f urther advanced than over Strecker stents and slightly more advanced t han over Wallstents. Pressure-related atrophy of the tunica media was least for Strecker stents and more pronounced but similar for Wallsten ts and Palmaz stents. Wallstent wire ends caused some wall trauma; sev eral femoral Palmaz stent struts protruded through the media. Conclusi ons The lower-hoop-strength, higher-profile tantalum Strecker stent is affected by vascular wall recoil and evokes a greater degree of neoin tima formation than the lower-profile, higher-hoop-strength Palmaz ste nt and Wallstent. Medial atrophy is pronounced outside the latter two stents. The rigid Palmaz stent can penetrate through the vascular wall in flexing arteries.