Coronary stent symmetry and vascular injury determine experimental restenosis

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 coeYcients 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. (Heart 2000;83:462-467)

Impact of Post-Procedural Intravascular Ultrasound Findings on Long-Term Results Following Self-Expanding Nitinol Stenting in Superficial Femoral Artery Lesions

“…In accordance with the present study, a previous intracoronary ultrasound study showed that asymmetric stent expansion was not associated with amount of neointimal tissue and restenosis rate. 26 In the present study, we found that stent over-expansion is not necessary after nitinol self-expanding stenting in SFA lesions. This finding may reflect continued stent expansion after implantation.…”

Role of Animal Models in Coronary Stenting

“…19,43,44 The sheep model yielded the relationship between stent asymmetry and neointimal growth, as well as confirming the relationship between injury and quantity of neointima in a different species. 45 The use of primates has been very limited. Using an externalized surgical upper limb fistula, or the carotid artery, studies were undertaken quantifying thrombus accumulation after stent implantation using radiolabelled platelets.…”

Sequential Structural and Fluid Dynamics Analysis of Balloon-Expandable Coronary Stents: A Multivariable Statistical Analysis

“…7,22,23,32,35,46,77,81,82,86 The mechanical impact of the investigated stents was evaluated in terms of the equivalent von Mises stress (ES) distribution predicted in the artery wall. The ES is calculated as follows:…”

“…Over the past two decades, several clinical studies have identified strong correlations between neointimal hyperplasia following coronary stent deployment and both stent-induced arterial injury 7,22,23,32,35,46,77,81,82,86 and altered vessel hemodynamics. 6,17,18,20,21,52,71,79,88 In light of these observations, a significant body of research has been carried out in this area.…”