Axial stent strut angle influences wall shear stress after stent implantation: analysis using 3D computational fluid dynamics models of stent foreshortening

INTRODUCTION: The success of vascular stents in the restoration of blood flow is limited by restenosis. Recent data generated from computational fluid dynamics (CFD) models suggest that the vascular geometry created by an implanted stent causes local alterations in wall shear stress (WSS) that are associated with neointimal hyperplasia (NH). Foreshortening is a potential limitation of stent design that may affect stent performance and the rate of restenosis. The angle created between axially aligned stent struts and the principal direction of blood flow varies with the degree to which the stent foreshortens after implantation. METHODS: In the current investigation, we tested the hypothesis that stent foreshortening adversely influences the distribution of WSS and WSS gradients using time-dependent 3D CFD simulations of normal arteries based on canine coronary artery measurements of diameter and blood flow. WSS and WSS gradients were calculated using conventional techniques in ideal (16 mm) and progressively foreshortened (14 and 12 mm) stented computational vessels. RESULTS: Stent foreshortening increased the intrastrut area of the luminal surface exposed to low WSS and elevated spatial WSS gradients. Progressive degrees of stent foreshortening were also associated with strut misalignment relative to the direction of blood flow as indicated by analysis of near-wall velocity vectors. CONCLUSION: The current results suggest that foreshortening may predispose the stented vessel to a higher risk of neointimal hyperplasia

Alterations in regional vascular geometry produced by theoretical stent implantation influence distributions of wall shear stress: analysis of a curved coronary artery using 3D computational fluid dynamics modeling

BACKGROUND: The success of stent implantation in the restoration of blood flow through areas of vascular narrowing is limited by restenosis. Several recent studies have suggested that the local geometric environment created by a deployed stent may influence regional blood flow characteristics and alter distributions of wall shear stress (WSS) after implantation, thereby rendering specific areas of the vessel wall more susceptible to neointimal hyperplasia and restenosis. Stents are most frequently implanted in curved vessels such as the coronary arteries, but most computational studies examining blood flow patterns through stented vessels conducted to date use linear, cylindrical geometric models. It appears highly probable that restenosis occurring after stent implantation in curved arteries also occurs as a consequence of changes in fluid dynamics that are established immediately after stent implantation. METHODS: In the current investigation, we tested the hypothesis that acute changes in stent-induced regional geometry influence distributions of WSS using 3D coronary artery CFD models implanted with stents that either conformed to or caused straightening of the primary curvature of the left anterior descending coronary artery. WSS obtained at several intervals during the cardiac cycle, time averaged WSS, and WSS gradients were calculated using conventional techniques. RESULTS: Implantation of a stent that causes straightening, rather than conforms to the natural curvature of the artery causes a reduction in the radius of curvature and subsequent increase in the Dean number within the stented region. This straightening leads to modest skewing of the velocity profile at the inlet and outlet of the stented region where alterations in indices of WSS are most pronounced. For example, time-averaged WSS in the proximal portion of the stent ranged from 8.91 to 11.7 dynes/cm(2 )along the pericardial luminal surface and 4.26 to 4.88 dynes/cm(2 )along the myocardial luminal surface of curved coronary arteries as compared to 8.31 dynes/cm(2 )observed throughout the stented region of a straight vessel implanted with an equivalent stent. CONCLUSION: The current results predicting large spatial and temporal variations in WSS at specific locations in curved arterial 3D CFD simulations are consistent with clinically observed sites of restenosis. If the findings of this idealized study translate to the clinical situation, the regional geometry established immediately after stent implantation may predispose portions of the stented vessel to a higher risk of neointimal hyperplasia and subsequent restenosis

Altered Mortality: Why the Quest for Immortality is Regaining Visibility in the Media

Media carry the message of the scientific community into the wider world, though sometimes it would be more appropriate to say: of a certain scientific group. For the field of bioethics, this is particularly true. From films such as Gattaca to TV series like Black Mirror, the relationship between science and science fiction appears evidently bidirectional. This relationship is not new of course, but this paper discusses quasi-science-fictional experiments such as that of Sergio Canavero and the recent TV series Altered Carbon through the lenses of the philosophical background they both rely on: immortality is achievable—and it should be sought with vehemence. At least by the rich

In defence of male circumcision

Controversies over the acceptability of male circumcision (MC) are not new to the international bioethical community. I do not expect to add much to the arguments or evidence presented elsewhere, but I want to acknowledge the often-overlooked political element in which the debate is entrenched. In fairness to those sympathetic to the circumcision ban, I will first introduce some supportive arguments to their position. Next, I will show the limits of those critiques, affirming that MC should not be outlawed in any liberal country, but that its permissibility only be evaluated within its medico-ethical dimension without the political charge often associated with the issue

Guantanamo and other cases of enforced medical treatment: A biopolitical analysis

This volume presents a number of controversial cases of enforced medical treatment from around the globe, providing for the first time a common, biopolitcal framework for all of them. Bringing together all these real cases guarantees that a new, more complete understanding of the topic will be within grasp for readers unacquainted with the aspects involved in these cases. On the one hand, readers interested mainly in the legal and medical dimensions of cases like those considered will benefit from the explanation of the biopolitical framework within which each case develops. On the other hand, those focusing on only one of the situations presented here will find the parallels between the cases an interesting expansion of the complexity of the problem. Despite the book's ambitious goal, for those willing to use it as supplemental material or interested in only one of the cases, the chapters can function as self-standing pieces to be read separately. This volume will be a valuable tool for both academics and professionals. Bioethicists in both the analytic and continental traditions, will find the book interesting for not only the specific concepts and issues considered, but also for its constructive bridging of the two schools of thought. In addition to philosophers, the structure of this work will also appeal to lawyers, doctors, human rights activists, and anyone concerned in the most disparate way with real-life cases of enforced medical treatment