Intraluminal thrombus and risk of rupture in patient specific abdominal aortic aneurysm – FSI modelling

Recent numerical studies of abdominal aortic aneurysm (AAA) suggest that intraluminal thrombus (ILT) may reduce the stress loading on the aneurysmal wall. Detailed fluid structure interaction (FSI) in the presence and absence of ILT may help predict AAA rupture risk better. Two patients, with varied AAA geometries and ILT structures, were studied and compared in detail. The patient specific 3D geometries were reconstructed from CT scans, and uncoupled FSI approach was applied. Complex flow trajectories within the AAA lumen indicated a viable mechanism for the formation and growth of the ILT. The resulting magnitude and location of the peak wall stresses was dependent on the shape of the AAA, and the ILT appeared to reduce wall stresses for both patients. Accordingly, the inclusion of ILT in stress analysis of AAA is of importance and would likely increase the accuracy of predicting AAA risk of rupture.     

Finite element and photoelastic modelling of an abdominal aortic aneurysm: a comparative study

Rupture prediction of abdominal aortic aneurysms (AAAs) remains a clinical challenge. Finite element analysis (FEA) may allow for improved identification for intervention timing, but the method needs further substantiation. In this study, experimental photoelastic method and finite element techniques were compared using an idealised AAA geometry. There was good agreement between the numerical and experimental results. At the proximal and distal end of the AAA model, the maximum differences in principle strain for an internal pressure of 120 mmHg had differences ranging from 0.03 to 10.01%. The maximum difference in principle strain for the photoelastic and the finite element model at a pressure of 120 mmHg was 0.167 and 0.158, respectively. The current research strengthens the case for using FEA as an adjunct to the current clinical practice of utilising diameter measurement for intervention timing.     

The “Gout of the Medici”: Making the modern diagnosis using paleopathology

Documentary sources show that painful joint disease afflicted several members of the Medici family, which dominated Renaissance Florence in Italy. The term frequently reported in contemporary archives to indicate these morbid episodes is “gout.” Paleopathology allows us to verify the nosological information obtained from the written documents and to clarify the nature of the rheumatological condition that afflicted the Medici.     

In‐vitro analysis of early calcification in aortic valvular interstitial cells using Laser‐Induced Breakdown Spectroscopy (LIBS)

Calcific aortic valve disease (CAVD) is a major cardiovascular disorder caused by osteogenic differentiation of valvular interstitial cells (VICs) within aortic valves. Conventional methods like colorimetric assays and histology fail to detect small calcium depositions during in‐vitro VIC cultures. Laser‐induced breakdown spectroscopy (LIBS) is a robust analytical tool used for inorganic materials characterizations, but relatively new to biomedical applications. We employ LIBS, for the first time, for quantitative in‐vitro detection of calcium depositions in VICs at various osteogenic differentiation stages. VICs isolated from porcine aortic valves were cultured in osteogenic media over various days. Colorimetric calcium assays based on arsenazo dye and Von Kossa staining measured the calcium depositions within VICs. Simultaneously, LIBS signatures for Ca I (422.67 nm) atomic emission lines were collected for estimating calcium depositions in lyophilized VIC samples. Our results indicate excellent linear correlation between the calcium assay and our LIBS measurements. Furthermore, unlike the assay results, the LIBS results could resolve calcium signals from cell samples with as early as 2 days of osteogenic culture. Quantitatively, the LIBS measurements establish the limit of detection for calcium content in VICs to be ～0.17±0.04 μg which indicates a 5‐fold improvement over calcium assay. Picture : Quantitative LIBS enables in‐vitro analysis for early stage detection of calcium deposition within aortic valvular interstitial cells (VICs).

     

Back Cover: In‐vitro analysis of early calcification in aortic valvular interstitial cells using Laser‐Induced Breakdown Spectroscopy (LIBS) (J. Biophotonics 1/2018)

Quantitative laser‐induced breakdown spectroscopy (LIBS) is successfully used for in‐vitro analysis of early stage calcification in aortic valvular interstitial cells (VICs). LIBS results indicate 5‐fold improvement in the detection limit of calcium deposition in VICs over cell histology techniques involving staining and colorimetric calcium assays. These results can establish LIBS at the forefront of early detection of calcification in VICs for pathological studies on Calcific Aortic Valve Disease (CAVD). Further details can be found in the article by Seyyed Ali Davari et al. ( e201600288 ).

     

Numerical simulation of aneurysmal haemodynamics with calibrated porous-medium models of flow-diverting stents

Modelling flow-diverting (FD) stents as porous media (PM) markedly improves the efficiency of computational fluid dynamics (CFD) simulations in the study of intracranial aneurysm treatment. Nonetheless, the parameters of PM models adopted for simulations up until now were rarely calibrated to match the represented FD structure. We therefore sought to evaluate the PM parameters for a representative variety of commercially available stents, so characterising the flow-diversion behaviours of different FD devices on the market.We generated fully-resolved geometries for treatments using PED, Silk+, FRED, and dual PED stents. We then correspondingly derived the calibrated PM parameters—permeability (k) and inertial resistance factor (C₂)—for each stent design from CFD simulations, to ensure the calibrated PM model has identical flow resistance to the FD stent it represents. With each of the calibrated PM models respectively deployed in two aneurysms, we studied the flow-diversion effects of these stent configurations.This work for the first time reported several sets of parameters for PM models, which is vital to address the current knowledge gap and rectify the errors in PM model simulations, thereby setting right the modelling protocol for future studies using PM models. The flow resistance parameters were strongly affected by porosity and effective thickness of the commercial stents, and thus accounted for in the PM models. Flow simulations using the PM stent models revealed differences in aneurysmal mass flowrate (MFR) and energy loss (EL) between various stent designs.This study improves the practicability of FD simulation by using calibrated PM models, providing an individualised method with improved simulation efficiency and accuracy.     

Magnesium: Effects on reperfusion arrhythmias and membrane potential in isolated rat hearts

Myocardial Na+,K+-ATPase was studied in patients with aortic valve disease, and myocardial Na+,K+- and Ca2+-ATPase were assessed in spontaneously hypertensive rats (SHR) and hereditary cardiomyopathic hamsters using methods ensuring high enzyme recovery. Na+,K+-ATPase was quantified by [3H]ouabain binding to intact myocardial biopsies from patients with aortic valve disease. Aortic stenosis, regurgitation and a combination hereof were compared with normal human heart and were associated with reductions of left ventricular [3H]ouabain binding site concentration (pmol/g wet weight) of 56, 46 and 60%, respectively (p < 0.01). Na+,K+ and Ca2+-ATPases were quantified by K+- and Ca2+-dependent p-nitrophenyl phosphatase (pNPPase) activity determinations in crude myocardial homogenates from SHR and hereditary cardiomyopathic hamsters. When SHR were compared to age-matched Wistar Kyoto (WKY) rats an increase in heart-body weight ratio of 75% (p < 0.001) was associated with reductions of K+- and Ca2+-dependent pNPPase activities (mol/min/g wet weight) of 42 (p < 0.01) and 27% (p < 0.05), respectively. When hereditary cardiomyopathic hamsters were compared to age-matched Syrian hamsters an increase in heart-body weight ratio of 69% (p < 0.001) was found to be associated with reductions in K+- and Ca2+-dependent pNPPase activities of 50 (p < 0.001) and 26% (p = 0.05), respectively. The reductions in Na+,K+- and Ca2+-ATPases were selective in relation to overall protein content and were not merely the outcome of increased myocardial mass relative to Na+,K+- and Ca2+-pumps. In conclusion, myocardial hypertrophy is in patients associated with reduced Na+,K+-ATPase concentration and in rodents with reduced Na+,K+- and Ca2+-ATPase concentrations. This may be of importance for development of heart f in hypertrophic heart disease.     

Numerical identification of the rupture locations in patient-specific abdominal aortic aneurysmsusing hemodynamic parameters

The rupture of an abdominal aortic aneurysm (AAA) is generally an unexpected event. Up to now, there is no agreement on an accurate criteria to predict the rupture risk of AAAs. This paper aims to numerically investigate the hemodynamics of three ruptured and one non-ruptured patient-specific AAA models to correlate local hemodynamic parameters with the rupture sites, and for the first time, this study introduced helicity as a potential index for the rupture potential of AAAs.3D reconstructions from CT scans were done. The simulation revealed that all the rupture sites were in regions of stagnation with near zero wall shear stress (WSS) but large WSS gradient (WSSG), which may explain the observation by the former researchers that the rupture site in the ruptured AAA has the lowest recorded wall thickness compared to other non-ruptured regions. Moreover, all the ruptures occurred at regions of zero helicity which represents a purely axial or circumferential flow. In addition, this study revealed that the double low region for the non-ruptured AAA was present with a thick layer of plaques, it suggests that the AAA rupture and the formation of atherosclerotic plaques may share a lot common physiological features. However, the fact that there are no plaques present in the walls of three RAAAs also indicates that AAA is not always a result of atherosclerosis. The current computational study may complement the maximum diameter, peak wall stress and other clinically relevant factors in AAA ruptures to identify the rupture sites of AAAs.     

老年患者全胸腔镜肺叶切除术后去止血治疗的安全性研究

目的:探讨全胸腔镜肺叶切除术后老年患者不应用止血药物的安全性。方法:回顾性分析65例成功施行全胸腔镜肺叶切除手术老年患者(年龄≥65周岁),按术后不同治疗方案分为研究组29例(术后未应用任何止血药物)及对照组36例(常规应用止血药物),对比两组患者术后胸腔引流情况、拔除引流管时间、住院时间、相关不良反应及并发症,评价全胸腔镜肺叶切除术后老年患者不应用止血药物的安全可靠性。结果:研究组术后24 h(310.6±54.6 m LVS 262.3±67.2 mL,P0.05)及48 h(225.4±47.3m LVS 195.5±66.4 mL,P0.05)胸腔引流量高于对照组,拔除引流管时间(4.23±2.84天VS 4.02±3.37天,P0.05)、住院时间(6.82±2.23天V S 6.53±3.21天,P0.05)及发生出血(3例V S 2例,P0.05)、栓塞风险均无显著差异,但应用止血药物增加了药物自身相关不良反应的风险,对照组中应用贝瑞凝止血治疗后,11例患者出现了消化道不适反应,1例患者出现头痛。结论:全胸腔镜肺叶切除术后老年患者,经术中严密止血后术后不应用止血药物是安全可靠的。