Coronary stent symmetry and vascular injury determine experimental restenosis

doi:10.1136/heart.83.4.462

Heart. 2000 April; 83(4): 462–467.

PMCID: PMC1729382

Coronary stent symmetry and vascular injury determine experimental restenosis

C Schulz, R Herrmann, C Beilharz, J Pasquantonio, and E Alt

1 Medizinische Klinik und Deutsches Herzzentrum, Klinikum rechts der Isar, Technische Universität München, Ismaningerstr 22, 81675 Munich, Germany.

This article has been cited by other articles in PMC.

Abstract

OBJECTIVE—To assess the impact of stent symmetry on restenosis using the coronary overstretch sheep model.
METHODS—Neointimal thickness, injury index, and percentage diameter and area stenosis were calculated by digital morphometry. The standard deviation of the angular burden was used to assess stent symmetry for each section.
MATERIALS—15 healthy Merino sheep (63-75 kg) underwent implantation of 30 slotted tube stents (7 mm). Restenosis was induced by calculated overstretch of the coronary artery. Twenty eight days after implantation, stents were excised and underwent histological examination using quantitative digital morphometry.
RESULTS—The severity of vessel injury was positively correlated with neointimal thickness and with percentage diameter and area stenosis (p < 0.001). Mean neointimal thickness and mean vascular injury per cross section were strongly related to the standard deviation of angular burden, with correlation coefficients of 0.6 and 0.8,respectively (p < 0.001).
CONCLUSIONS—The well known relation between vascular injury and restenosis was confirmed, and a new relation was discovered between stent asymmetry and restenosis. If these results apply to human coronary arteries, restenosis may also be dependent on the degree of asymmetric stent expansion. These results should influence the development of new stent designs to reduce asymmetric stent expansion, leading to a more homogeneous strain distribution in stented coronary segments.

Keywords: stent symmetry; vascular injury; restenosis; interventional cardiology

Figure 1

Scatterplot of mean vascular injury score versus mean neointimal thickness per section. There is a proportional relation. The scatter increases for increasing depth of injury.

Figure 2

Scatterplot of mean vascular injury versus percentage area stenosis per section. There is a proportional relation, as in fig 1.

Figure 3

Low power photomicrographs from methylmethacrylate embedded sections from sheep coronary arteries 28 days after stent implantation. (Paragon stain, magnification × 14.) Representative cross section with symmetric (A) and (more ...)

Figure 4

Scatterplot of standard deviation of angular burden versus mean neointimal thickness per section. The proportional relation indicates that restenosis is related to asymmetric stent expansion.

Figure 5

Scatterplot of standard deviation of angular burden versus average injury score per section. The injury vessel score is related to the standard deviation of the angular burden, showing that asymmetric stent deployment leads to increased vascular injury. (more ...)

Figure 6

Scanning electron microscopy (× 27.5 magnification) showing a strut intersection of a slotted tube stent 28 days after implantation in a sheep coronary artery. Note the badly torqued struts in that area of pronounced stent (more ...)

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