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Understanding aortic root in vivo biomechanics can help in elucidating key mechanisms involved in aortic root pathologies and in the outcome of their surgical treatment. Numerical models can provide useful quantitative information. For this to be reliable, detailed aortic root anatomy should be captured. Also, since the aortic root is never unloaded throughout the cardiac cycle, the modeled geometry should be consistent with the in vivo loads acting on it. Achieving such consistency is still a challenge, which was tackled only by few numerical studies. Here we propose and describe in detail a new approach to the finite element modeling of aortic root in vivo structural mechanics. Our approach exploits the anatomical information yielded by magnetic resonance imaging by reconstructing the 3-dimensional end-diastolic geometry of the aortic root and makes the reconstructed geometry consistent with end-diastolic loading conditions through the estimation of the corresponding prestresses field. We implemented our approach through a semiautomated modeling pipeline, and we applied it to quantify aortic root biomechanics in 4 healthy participants. Computed results highlighted that including prestresses into the model allowed for pressurizing the aortic root to the end-diastolic pressure while matching the image-based ground truth data. Aortic root dynamics, tissues strains, and stresses computed at relevant time points through the cardiac cycle were consistent with a broad set of data from previous computational and in vivo studies, strongly suggesting the potential of the method. Also, results highlighted the major role played by the anatomy in driving aortic root biomechanics. [ABSTRACT FROM AUTHOR]

OBJECTIVE: This cross-sectional study explored differences in the impact of self-reported coping style, self-esteem and perceived support on the psychological adjustment of homeless and housed female youth. METHOD: Data were obtained from homeless female youth (n = 72, M = 17.5 years) accessing an emergency shelter in a large Canadian urban centre and a comparison group of housed females (n = 102 ; M = 17.2 years) from local high schools who had never resided in a shelter. RESULTS: Homeless youth reported lower self-worth, increased suicidal behaviour, less perceived parental support and higher levels of depressive symptoms and both internalizing and externalizing behaviour problems than housed youth. Hierarchical regression analyses indicated that disengagement coping was a significant predictor of depressive symptoms and both internalizing and externalizing behaviour problems in homeless and housed youth. CONCLUSIONS: Findings reflect the merit of considering coping style, parental support and self-worth in the presentation of depressive symptoms and behaviour problems in homeless and housed female youth. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate the acceptability and feasibility of the I Promise Program (IPP), a driving program developed for families with young new drivers (YNDs). Design, setting, and subjects: The IPP consists of a contract between parents and YNDs and a rear window decal (sticker). Program acceptability was assessed through Four focus groups with 40 young new drivers (YND), two with 19 parents of YNDs, and two with 15 community members. To determine whether the program's design, materials, and procedures were working as planned, 51 families participated in a six month pilot project. Telephone and in-person interviews were conducted at months 1 and 6, respectively. Results: Participants had problems with the acceptability of the program's underlying message; content, format, and language of the materials; program cost; and proposed participant incentives. Thirty eight (75%) families completed the six month pilot. Most YNDs (75%) and parents (85%) identified the contract as a useful communication tool. Despite positive initial reactions, 50% of YNDs did not recall the content of the contract after six months. Sixty eight percent of families had problems with the decal (for example, did not stay affixed, colors faded) and only 17% of YNDs reported a lasting impact on their driving. Only 20% of families chose to continue in the program after the pilot. Conclusions: These results highlight the importance of formative and process evaluation in the development of a new prevention strategy to assess a strategy's acceptability and feasibility. In response to participants' feedback, revisions made to the program's materials and delivery model included making its two key components—the contract and decal—available online, independent of each other, and free of charge. [ABSTRACT FROM AUTHOR]

A Finite Element workflow for the multiscale analysis of the aortic valve biomechanics was developed and applied to three physiological anatomies with the aim of describing the aortic valve interstitial cells biomechanical milieu in physiological conditions, capturing the effect of subject-specific and leaflet-specific anatomical features from the organ down to the cell scale. A mixed approach was used to transfer organ-scale information down to the cell-scale. Displacement data from the organ model were used to impose kinematic boundary conditions to the tissue model, while stress data from the latter were used to impose loading boundary conditions to the cell level. Peak of radial leaflet strains was correlated with leaflet extent variability at the organ scale, while circumferential leaflet strains varied over a narrow range of values regardless of leaflet extent. The dependency of leaflet biomechanics on the leaflet-specific anatomy observed at the organ length-scale is reflected, and to some extent emphasized, into the results obtained at the lower length-scales. At the tissue length-scale, the peak diastolic circumferential and radial stresses computed in the fibrosa correlated with the leaflet surface area. At the cell length-scale, the difference between the strains in two main directions, and between the respective relationships with the specific leaflet anatomy, was even more evident; cell strains in the radial direction varied over a relatively wide range ( 0.36 - 0.87 ) with a strong correlation with the organ length-scale radial strain ( R 2 = 0.95 ); conversely, circumferential cell strains spanned a very narrow range ( 0.75 - 0.88 ) showing no correlation with the circumferential strain at the organ level ( R 2 = 0.02 ). Within the proposed simulation framework, being able to account for the actual anatomical features of the aortic valve leaflets allowed to gain insight into their effect on the structural mechanics of the leaflets at all length-scales, down to the cell scale. [ABSTRACT FROM AUTHOR]

Patient-specific finite element (FE) models can assess the impact of mitral valve (MV) repair on the complex MV anatomy and function. However, FE excessive time requirements hamper their use for surgical planning; mass-spring models (MSMs) represent a more approximate approach but can provide almost real-time simulations. On this basis, we implemented MSMs of three healthy MVs from cardiac magnetic resonance (cMR) imaging to simulate the systolic MV closure, including the in vivo papillary muscles and annular kinematics, and the anisotropic and non-linear mechanical response of MV tissues. To test MSM reliability we compared the systolic peak configurations computed by MSMs and FE: mismatches by less than twice the in-plane cMR image resolution were detected over 75% of the leaflets’ surface, independently of the MSM mesh refinement and of the specific MV anatomy. Data on MSMs time-efficiency and data from the comparison of MSMs vs. FE models suggest that MSM could represent a suitable trade-off between almost real-time simulations and reliability when computing MV systolic configuration, with the potential to be used in a clinical setting either as a support to the decisional process or as a virtual training tool. [ABSTRACT FROM AUTHOR]

Bicuspid aortic valve (BAV), i.e. the fusion of two aortic valve cusps, is the most frequent congenital cardiac malformation. Its progression is often characterized by accelerated leaflet calcification and aortic wall dilation. These processes are likely enhanced by altered biomechanical stimuli, including fluid-dynamic wall shear stresses (WSS) acting on both the aortic wall and the aortic valve. Several studies have proposed the exploitation of 4D-flow magnetic resonance imaging sequences to characterize abnormal in vivo WSS in BAV-affected patients, to support prognosis and timing of intervention. However, current methods fail to quantify WSS peak values. On this basis, we developed two new methods for the improved quantification of in vivo WSS acting on the aortic wall based on 4D-flow data. We tested both methods separately and in combination on synthetic datasets obtained by two computational fluid-dynamics (CFD) models of the aorta with healthy and bicuspid aortic valve. Tests highlighted the need for data spatial resolution at least comparable to current clinical guidelines, the low sensitivity of the methods to data noise, and their capability, when used jointly, to compute more realistic peak WSS values as compared to state-of-the-art methods. The integrated application of the two methods on the real 4D-flow data from a preliminary cohort of three healthy volunteers and three BAV-affected patients confirmed these indications. In particular, quantified WSS peak values were one order of magnitude higher than those reported in previous 4D-flow studies, and much closer to those computed by highly time- and space-resolved CFD simulations. [ABSTRACT FROM AUTHOR]