Author(s)

M.R. Hyre, R.M. Pulliam & J.C. Squire

Abstract

R estenosis remains a significant problem in coronary intervention. Although stent migrations, collapses, and positioning difficulties remain serious issues, it is the problem of restenosis which is the most common long term problem in treating atherosclerotic coronary arteries with stents. Although much attention has focused on biocompatibility, thrombosis and neointimal pathology, less attention has been given to matching stents to the inflation balloon, artery and occlusion size. Balloons are typically sized 1–2 mm longer than endovascular stents, yet the effects of the degree of balloon overhang are unknown. In this study, a computational model capable of predicting balloon/stent/artery interactions and their effects on arterial stresses was developed to assess the effects of length mismatch on stent expansion characteristics and arterial stresses. Results from this study indicate that maximum arterial stress at balloon contact is approximately proportional to the degree of balloon overhang. A 100% increase in balloon overhang results in a 4% increase in maximum endflare and a 39% change in the peak arterial stress. However, at the end of expansion, which is of the most clinical importance, the increase in maximum endflare is 2% and the increase in maximum arterial stress is 93% at the balloon point of contact and 45% at the point of contact with the far proximal and distal ends of the stent. When comparing the results of calcified and cellular plaque, a maximum endflare of about 55% was observed for both the calcified and cellular plaque cases during expansion. At the end of expansion the increase in maximum endflare was 10% for the cellular plaque and 40% of the calcified plaque. The peak equivalent stress seen by the artery was about 100% larger in the cellular case than in the calcified plaque case.

Keywords

balloon inflation, finite element modeling, stenosis, stent inflation