Nonuniform Strut Distribution Correlates With More Neointimal Hyperplasia After Sirolimus-Eluting Stent Implantation

Abstract

Background-Little is known about causes of intimal hyperplasia (IH) after sirolimus-eluting stent (SES) implantation.Methods and Results-Intravascular ultrasound was performed in 24 lesions with intra-SES restenosis and a comparison group of 25 nonrestenotic SESs. To assess stent strut distribution, the maximum interstrut angle was measured with a protractor centered on the stent, and the visible struts were counted and normalized for the number of stent cells. In SES restenosis patients, minimum lumen site was compared with image slices 2.5, 5.0, 7.5, and 10.0 mm proximal and distal to this site. The minimum lumen site had a smaller IVUS lumen area at follow-up (2.7Ϯ0.9 versus 6.2Ϯ1.9 mm 2 ; PϽ0.01), larger maximum interstrut angle (135Ϯ39°versus 72Ϯ23°; PϽ0.01), larger IH area (3.4Ϯ1.5 versus 0.6Ϯ1.1 mm 2 ; PϽ0.01) and thickness (0.7Ϯ0.3 versus 0.1Ϯ0.2 mm; PϽ0.01) at maximum interstrut angle, and fewer stent struts (4.9Ϯ1.0 versus 6.0Ϯ0.5; PϽ0.01) even when normalized for the number of stent cells (0.78Ϯ0.15 versus 0.97Ϯ0.07; PϽ0.01). Compared with nonrestenotic SES, the restenosis lesions also had a smaller minimal lumen area, larger IH area, thicker IH at maximum interstrut angle, fewer stent struts, and larger maximum interstrut angle. Multivariate analysis identified the number of visualized stent struts normalized for the number of stent cells and maximum interstrut angle as the only independent IVUS predictor of IH cross-sectional area (PϽ0.01 and PϽ0.01), minimum lumen area (PϽ0.01 and PϽ0.01), and IH thickness (PϽ0.01 and PϽ0.01). Conclusions-The number and distribution of stent struts affect the amount of neointima after SES implantation.

A New 3-D Automated Computational Method to Evaluate In-Stent Neointimal Hyperplasia in In-Vivo Intravascular Optical Coherence Tomography Pullbacks

“…Another parameter measured is the maximum angle between adjacent stent struts. As reported by Takebayashi et al [9], this measurement correlates with the NIH thickness in IVUS-based studies. NIH thickness was also evaluated looking at the lumen cross-sectional area (L-CSA), the stent cross-sectional area (S-CSA), minimum, maximum, and average distance between the lumen boundary and the stent.…”

“…A large-scale evaluation of OCT pullback stent analysis will be necessary to further correlate the degree of NIH and circumferential stent strut distribution, as suggested previously by IVUS [9].…”

“…5. Schematic of struts and related measurements calculated for stent follow-up analysis, adapted from [9]. Maximum interstrut angle, LA (lumen cross-sectional area: L-CSA), IH (=Stent CSA -L-CSA), distances between the lumen and the stent contours (here c is depicted: the maximum distance=thickness of the NIH).…”

“…Studies have shown that nonuniform circumferential stent strut distribution affects local drug concentration [8]. Number and distribution of the stent struts might also affect the magnitude of NIH after stent implantation in human coronary arteries [9]. Therefore, tracking of stent position/malapposition and neointimal tissue growth after stent implantation is clinically important.…”

Predictive Factors for Restenosis after Drug-Eluting Stent Implantation

“…34) In addition, stent fracture is rarely related to very focal intrastent restenosis despite complete abolition of intimal hyperplasia in the remainder of the stented segment. 35) Overall, the published reports have suggested that residual stenosis is a significant component of the restenosis problem, and this indicates that achieving a larger lumen area with adequate stent expansion remains an important strategy for reducing restenosis, even in the DES era.…”