Tortuosity of coronary bifurcation as a potential local risk factor for atherosclerosis: CFD steady state study based on in vivo dynamic CT measurements.

The purpose of the present study was to determine whether in vivo bifurcation geometric factors would permit prediction of the risk of atherosclerosis. It is worldwide accepted that low or oscillatory wall shear stress (WSS) is a robust hemodynamic factor in the development of atherosclerotic plaque and has a strong correlation with the local site of plaque deposition. However, it still remains unclear how coronary bifurcation geometries are correlated with such hemodynamic forces. Computational fluid dynamics simulations were performed on left main (LM) coronary bifurcation geometries derived from CT of eight patients without significant atherosclerosis. WSS amplitudes were accurately quantified at two high risk zones of atherosclerosis, namely at proximal left anterior descending artery (LAD) and at proximal left circumflex artery (LCx), and also at three high WSS concentration sites near the bifurcation. Statistical analysis was used to highlight relationships between WSS amplitudes calculated at these five zones of interest and various geometric factors. The tortuosity index of the LM-LAD segment appears to be an emergent geometric factor in determining the low WSS amplitude at proximal LAD. Strong correlations were found between the high WSS amplitudes calculated at the endothelial regions close to the flow divider. This study not only demonstrated that CT imaging studies of local risk factor for atherosclerosis could be clinically performed, but also showed that tortuosity of LM-LAD coronary branch could be used as a surrogate marker for the onset of atherosclerosis.

Ex vivo and preclinical assessment of an endothelial progenitor cell capturing bioengineered stent.

Although drug-eluting stents (DES) have significantly reduced the rates of restenosis as compared to bare metal stents, late stent thrombosis remains a major drawback, especially for "off-label" use. Delayed arterial healing, characterized by persistent fibrin deposition and poor endothelialization, has been shown to correlate with late DES thrombosis. To overcome these limitations, a "pro-healing" approach has been developed to capture circulating endothelial progenitor cells (EPC) to enhance endothelialization of the stent surface. EPC have the ability to migrate to sites of vascular injury and aid the regeneration of damaged and dysfunctional endothelium. Clinically, the safety of EPC-capture stent has been proven in numerous clinical trials with low incidence of late stent thrombosis. The focus of this review is to demonstrate the efficacy of the Genous stent in preclinical studies, specifically to show the effectiveness of the anti-CD34+ coating in promoting endothelialization and reducing thrombogenicity.

Endovascular histologic effects of ultrathin gold- or vitronectin-coated platinum aneurysm coils in a rodent arterial occlusion model: a preliminary investigation.

BACKGROUND AND PURPOSE: Novel stratagems to improve the efficacy of platinum coils in occluding cerebral aneurysms have primarily involved coating coils with materials thought likely to provoke more desirable histologic reactions. No investigations to date, however, have evaluated the utility of gold or vitronectin coatings, despite known endovascular histologic effects of these agents, which may be favorable for treating cerebral aneurysms. This study was conducted to evaluate the degree of endovascular histologic change associated with ultrathin gold- or vitronectin-coated platinum coils. It was hypothesized that such coatings would increase intra-aneurysmal intimal hyperplasia and the degree of luminal occlusion compared with standard platinum coils. MATERIALS AND METHODS: The ligated carotid artery rat model was used to study 4 different aneurysm coil conditions: no coil (sham-surgery controls), uncoated platinum coil, and gold- or vitronectin-coated platinum coil. Two weeks postimplantation, the aneurysms were harvested and stained with hematoxylin-eosin. Slides were evaluated for the degree of neointimal response by a pathologist blinded to treatment. Additional quantitative evaluation was performed blindly by using the ratio of intimal-to-luminal cross-sectional area. RESULTS: A gold- or vitronectin-coated platinum aneurysm coil produced a statistically significant increase in neointimal response compared with a sham (no coil). Arterial segments treated with gold-coated platinum coils also demonstrated a statistically significant 100% increase in neointimal response compared with those treated with bare platinum coils. CONCLUSIONS: In concordance with our hypothesis, ultrathin coatings of gold provoked a neointimal response and degree of luminal occlusion greater than that of plain platinum aneurysm coils in a rat arterial occlusion model.

Investigating sacroplasty: technical considerations and finite element analysis of polymethylmethacrylate infusion into cadaveric sacrum.

BACKGROUND AND PURPOSE: Sacroplasty is not as routinely performed as vertebroplasty, possibly due to technical challenges and the paucity of data regarding subsequent outcomes. The first goal of the present investigation was to describe a technique for sacroplasty that facilitates safe needle placement and polymethylmethacrylate (PMMA) extrusion. The second goal was to perform finite element analysis (FEA) by using a geometric model of sacral fracture to identify mechanical outcomes of sacroplasty. MATERIALS AND METHODS: Sacroplasty was performed on fresh pelvis specimens (n=4) under biplane fluoroscopy. Cadavers were imaged via CT before and after sacroplasty and volume rendered to examine needle placement and PMMA extrusion. The volume-rendered CT data were then used to generate geometric models of the intact, fractured, and cement-augmented fractured sacrum for comparison by using FEA. RESULTS: CT data demonstrate that safe injection needle placement and PMMA delivery may be facilitated by orienting the needle parallel to the L5-S1 interspace and ipsilateral sacroiliac joint, then targeting the superolateral sacral ala within an area bounded by a line lateral to the posterior foraminal openings and a line superimposed on the medial edge of the sacroiliac joint. FEA revealed that simulated sacroplasty decreased maximal principal stress at the point of sacral fracture propagation by 83% and fracture gap micromotion by 48%. CONCLUSION: Sacral landmarks can be used to place PMMA safely where sacral fractures occur. FEA suggests that sacroplasty may decrease fracture-associated mechanical stress and micromotion, which may contribute to patient reports of decreased pain and increased mobility postsacroplasty.