Impact of the cross-sectional geometry of the post-deployment coronary stent on in-stent neointimal hyperplasia: an intravascular ultrasound study.

To establish the relationship between the cross-sectional geometry of the post-deployment stent and the degree of in-stent neointimal hyperplasia (INH), intravascular ultrasound (IVUS) was used to examine cross-sections of the coronary arteries from 23 patients with coronary stents 6 months after implantation. Stent cross-sectional area (Sa) and stent perimeter (Sp) from 200 stent cross-sections, and the stent radius (Sr) and thickness of INH (Id) of 2,880 radial axes, were measured, and the mean degree of roundness (Rd) of stent cross-section was calculated for each stent as Rd=4piSa/Sp2. The degree of deformity (Df) of the stent cross-section was also calculated by comparing it with a hypothetical circle (the area of this hypothetical circle was equal to the Sa): Df=Sr/R, where R is the radius of the hypothetical circle. The area of INH was significantly larger in the Rd<0.87 group (n=84) than in the Rd> or =0.87 group (n=116) (3.83+/-1.26 vs 3.16+/-1.32 mm2, p<0.0005). There were significant differences in the thickness of INH among the 3 groups classified by the value of Df (Df<0.95: n=425, 0.21+/-0.12mm; 0.95< or =Df<1.05: n=2008, 0.29+/-0.15mm; Df> or =1.05: n=447, 0.34+/-0.15mm, overall p<0.0001). These data suggest that in-stent neointimal proliferation is more likely to occur in stented coronary arteries with a more oval than rounded cross-section, and particularly within the more pronounced and curved portion of the oval.