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

The Singleton case: Enforcing medical treatment to put a person to death

In October 2003 the Supreme Court of the United States allowed Arkansas officials to force Charles Laverne Singleton, a schizophrenic prisoner convicted of murder, to take drugs that would render him sane enough to be executed. On January 6 2004 he was killed by lethal injection, raising many ethical questions. By reference to the Singleton case, this article will analyse in both moral and legal terms the controversial justifications of the enforced medical treatment of death-row inmates. Starting with a description of the Singleton case, I will highlight the prima facie reasons for which this case is problematic and merits attention. Next, I will consider the justification of punishment in Western society and, in that context, the evolution of the notion of insanity in the assessment of criminal responsibility during the past two centuries, both in the US and the UK. In doing so, I will take into account the moral justification used to enforce treatment, looking at the conflict between the prisoner's right to treatment and his right to refuse medication where not justified by outcomes that can be reasonably expected to be positive for the individual. Finally, in contrast with some retributivist arguments in favour of enforced treatment to enable execution, I will propose a possible alternative, necessary if we are to consistently uphold the notion of autonomy. © 2013 Springer Science+Business Media Dordrecht

The Authors Reply

A reply by the author of "Scholarly Discussion of Infanticide?" to "The Arguments Matter," by Don Marquis, "The Importance of Rationality," by G. Owen Schaeffer, and "Reasons and Freedom," by Alberto Giubilini and Francesca Minerva. © 2013 by The Hastings Center

Uses and abuses of the body in the postmodern era

This paper will focus on two controversial cases relating to the [mis]use of the notion of autonomy in situations of life and death. While in one case the patient's will to die was not respected, in the other there was no attempt to save the life of the individual. I have chosen to put these two specific cases in parallel for the fact that in both instances the presence of some kind of mental impairment is not given at all. Yet, in both situations there is substantial reference to some type of temporary competence -as this is the key element that, allegedly, should function as decisive to assess the moral and legal justification behind the decision to enforce -or not- medical treatment upon the protagonists of these two very sad stories. Following on from the objective of this paper thus, the contraposition of these two cases will provide us with a vivid image of the practical implications of using the notion of autonomy (here presented under the form of a more psychiatric-oriented term: competence) in an inconsistent manner within the Western world (US and EU). Raising many doubts over its appropriateness