Morphological Analysis of Healthy Aortic Arch.

OBJECTIVE/BACKGROUND: This study aimed to describe an arch morphology protocol in a healthy population, and to assess the impact of age and sex. METHODS: A retrospective morphology evaluation was conducted in a population with no personal history of thoracic aorta surgery or pathology, through computed tomography (CT) imaging analysis, using a standardised protocol. Based on centreline three dimensional coordinates, a single investigator calculated a series of parameters in the arch zones and in the total arch, using Matlab scripts. These were categorized as: (i) morphometric data: diameter, length and aortic angle of each zone, total arch angle, and length; (ii) geometric data: tortuosity index (TI), arch width, assimilated curvature radius (CRi), and attachment zone angles. Student or Mann-Whitney tests were used to compare parameter means. Their variability with age and sex was assessed through univariate and multivariate regression analysis. RESULTS: CT images from 123 subjects (mean ± SD age 53 ± 19 years) were reviewed. Significant correlation between age and morphology was found. The aorta expanded homogeneously and stretched heterogeneously with age because of posterior arch elongation. TI decrease, CRi, and attachment zone angle increase were also observed with aging. Age remained significantly associated with these morphological parameters, independently of body surface area and hypertension. Sex also affected morphology: longer total arch length and higher CRarch in men; lower zone 3 attachment angle in women CONCLUSION: Using mathematical algorithms, and with a view to improving endovascular arch treatment, this study provides a standardised arch morphology protocol and objectively identifies both age related evolution and sex related variation in the different zones.

Risk Factor Analysis for the Mal-Positioning of Thoracic Aortic Stent Grafts.

OBJECTIVE: The present study aimed at quantifying mal-positioning during thoracic endovascular aortic repair and analysing the extent to which anatomical factors influence the exact stent graft positioning. METHODS: A retrospective review was conducted of patients treated between 2007 and 2014 with a stent graft for whom proximal landing zones (LZ) could be precisely located by anatomical fixed landmarks, that is LZ 1, 2, or 3. The study included 66 patients (54 men; mean age 51 years, range 17-83 years) treated for traumatic aortic rupture (n = 27), type B aortic dissection (n = 21), thoracic aortic aneurysm (n = 8), penetrating aortic ulcer (n = 5), intramural hematoma (n = 1), and floating aortic thrombus (n = 4). Pharmacologic hemodynamic control was systematically obtained during stent graft deployment. Pre- and post-operative computed tomographic angiography was reviewed to quantify the distance between planned and achieved LZ and to analyze different anatomical factors: iliac diameter, calcification degree, aortic angulation at the proximal deployment zone, and tortuosity index (TI). RESULTS: Primary endoleak was noted in seven cases (10%): five type I (7%) and two type II (3%). Over a mean 35 month follow up (range 3-95 months), secondary endoleak was detected in two patients (3%), both type I, and stent graft migration was seen in three patients. Mal-positioning varied from 2 to 15 mm. A cutoff value of 11 mm was identified as an adverse event risk. Univariate analysis showed that TI and LZ were significantly associated with mal-positioning (p = .01, p = .04 respectively), and that aortic angulation tends to reach significance (p = .08). No influence of deployment mechanism (p = .50) or stent graft generation (p = .71) or access-related factors was observed. Multivariate analysis identified TI as the unique independent risk factor of mal-positioning (OR 241, 95% CI 1-6,149, p = .05). A TI >1.68 was optimal for inaccurate deployment prediction. CONCLUSION: TI calculation can be useful to anticipate difficulties during stent graft deployment and to reduce mal-positioning.

Quantitative MRI water content mapping of porcine intervertebral disc during uniaxial compression.

BACKGROUND: Intervertebral disc (IVD) diseases are major public health problem in industrialized countries where they affect a large proportion of the population. In particular, IVD degeneration is considered to be one of the leading causes of pain consultation and sick leave. The aim of this study was to develop a new method for assessing the functionality of IVD in order to diagnose IVD degeneration. METHODS: For this purpose, we have designed a specific device that enables to mechanically load porcine IVD ex vivo in the 4.7-Tesla horizontal superconducting magnet of a magnetic resonance (MR) scanner. Proton density weighted imaging (ρH-MRI) of the samples was acquired. FINDINGS: The post-processing on MR images allowed (1) to reconstruct the 3D deformation under a known mechanical load and (2) to infer the IVD porosity assuming an incompressible poroelastic model. INTERPRETATION: This study demonstrates the ability to follow the change in morphology and hydration of an IVD using MR measurements, thereby providing valued information for a better understanding of IVD function.

Risk Factor Analysis of Bird Beak Occurrence after Thoracic Endovascular Aortic Repair.

OBJECTIVES: The aim was to analyze the role played by anatomy and stent graft in the incidence of incomplete apposition to aortic arch. METHODS: Between 2007 and 2014 data including available and suitable computed tomographic angiography (CTA) imaging of patients who had undergone thoracic endovascular aortic repair were reviewed. The study included 80 patients (65 men, 54 ± 21 years) treated for traumatic aortic rupture (n = 27), thoracic aortic aneurysm (n = 15), type B aortic dissection (n = 24), penetrating aortic ulcer (n = 5), intramural hematoma (n = 2), aorto-oesophageal fistula (n = 2), and aortic mural thrombus (n = 5). Pre- and post-operative CTA images were analyzed to characterize bird beak in terms of length and angle, and to calculate aortic angulation within a 30 mm range at the proximal deployment zone. RESULTS: Bird beak configuration was detected in 46 patients (57%): mean stent protrusion length was 16 mm (range: 8-29 mm) and mean bird beak angle was 20° (range: 7-40°). The bird beak effect was significantly more frequent after traumatic aortic rupture treatment (p = .05) and in landing zone 2 (p = .01). No influence of either stent graft type or generation, or degree of oversizing was observed (p = .29, p = .28, p = .81 respectively). However, the mean aortic angle of patients with bird beak was higher in the Pro-form group than that in the Zenith TX2 group (62° vs. 48°, p = .13). Multivariate analysis identified the aortic angle of the deployment zone as the unique independent risk factor of malapposition (HR = 1.05, 95% CI 1-1.10, p = .005). The cutoff value of 51° was found to be predictive of bird beak occurrence with a sensitivity of 58% and a specificity of 85%. CONCLUSIONS: Assessment of proximal landing zone morphology to avoid deployment zones generating an aortic angle of over 50° can be recommended to improve aortic curvature apposition with the current available devices.

New experimental protocols for tensile testing of abdominal aortic analogues.

This work proposes an in vitro tensile testing protocol that is able to characterize abdominal aortic (AA) analogues under physiologically inspired mechanical loadings. Kinematic parameters are defined in agreement with in vivo measurements of aortic dynamics. A specific focus is given to the choice of the applied loading rates, deriving from the knowledge of aortic Peterson modulus and blood pressure variations from diastolic to systolic instants. The influence of physiological elongation rates has been tested on both porcine AAs and a thermoplastic polyurethane (TPU) material used to elaborate AA analogues. The diastolic and systolic elongation rates estimates vary between orders of magnitude O(10(-2)) and O(10(-1))s(-1). Negligible differences are obtained when comparing stress-elongation responses between both physiological elongation rates. In contrast, a noticeable stiffening of the TPU mechanical response is observed compared to that obtained under the common low traction rate of O(10(-3))s(-1). This work shows how relevant physiological elongation rates can be evaluated as a function of age, gender and pathological context.

Numerical simulations of unsteady flows in a stenosed coronary bypass graft.

Using the finite element method, physiological blood flows through a three-dimensional model of a coronary graft are numerically analysed. The model includes a stenosis shape in the host artery upstream from the anastomosis. Recirculating areas, secondary flows, wall shear stress (WSS) and spatial wall shear stress gradients (WSSGs) are studied for different flow repartitions and at different times in the cycle. The temporal and spatial evolutions of the recirculating areas downstream from the stenosis, their interactions with the flow issued from the graft and their associated WSSs highlight that the presence of the stenosis in the recipient artery is essential for prediction of the evolution of a grafting at the beginning of its implantation. The areas downstream from the stenosis expansion, non-existent for a host artery without stenosis, are submitted to low and oscillating WSS between -0.5 and 0 Nm(-2). The stagnation point on the recipient artery floor is subjected to high positive and negative WSSGnd values, and its location is dependent on the residual flow through the stenosis.

Ethylene glycol ethers as hemopoietic toxins--in vitro studies of acute exposure.

Ethylene glycol ethers and their acetate derivatives were analyzed for their toxicity in vitro on several hemopoietic cell lines, either growth-factor-dependent or leukemic, in mouse, rat, and human species. Considering the concentrations that reduced the cell viability in culture by 50%, most of the ethylene glycol ethers and in particular ethylene glycol monoethyl ether (EGEE) or ethylene glycol monobutyl ether (EGBE) should be considered as hemopoietic toxins. EGBE was found to be the most potent toxin on the human promyelocytic cell line, NB4 (median inhibitory concentration (IC50) 5 mM at 6 h; IC50 0.1 mM at 96 h) but also on the factor-dependent cell line DA1 (IC50 80 microM at 48 h). Factor-dependent cell lines were not significantly more sensitive than leukemic cell lines. The toxicity of these compounds falls in the same range of concentration as benzene or phenol, but hydroquinone was significantly more toxic in the same assay (IC50 3-15 microM at 48 h). Toxic effects increased linearly with time. The toxicity of ethylene glycol ethers was confirmed by both assays for colony-forming units in culture medium (CFU-C) (human blood cord cells) and murine bone marrow long-term culture (IC50 5-10 mM). Stromal cells in the adherent layer were more resistant than hemopoietic cells. An all or none toxicity was found within a narrow range of concentration (2-5 mM for EGBE), and chronic exposure over two months did not show cumulative effects on the culture cellularity. The possibility that fibroblastic or macrophage cells worked at the detoxification of the culture is suggested. Results are discussed with regard to epidemiological and in vivo experimental data presently available.

Glycol alkyl ethers as hemopoietic toxins.

Since 1971, glycol alkyl ethers have taken progressively the place of aromatic solvents including benzene. Experimental data point out to a possible toxicity on bone marrow, responsible of hypoplasia and even acute leukemia.