Fluid-structure interactions of peripheral arteries using a coupled in silico and in vitro approach.

Vascular compliance is considered both a cause and a consequence of cardiovascular disease and a significant factor in the mid- and long-term patency of vascular grafts. However, the biomechanical effects of localised changes in compliance cannot be satisfactorily studied with the available medical imaging technologies or surgical simulation materials. To address this unmet need, we developed a coupled silico-vitro platform which allows for the validation of numerical fluid-structure interaction results as a numerical model and physical prototype. This numerical one-way and two-way fluid-structure interaction study is based on a three-dimensional computer model of an idealised femoral artery which is validated against patient measurements derived from the literature. The numerical results are then compared with experimental values collected from compliant arterial phantoms via direct pressurisation and ring tensile testing. Phantoms within a compliance range of 1.4-68.0%/100 mmHg were fabricated via additive manufacturing and silicone casting, then mechanically characterised via ring tensile testing and optical analysis under direct pressurisation with moderately statistically significant differences in measured compliance ranging between 10 and 20% for the two methods. One-way fluid-structure interaction coupling underestimated arterial wall compliance by up to 14.7% compared with two-way coupled models. Overall, Solaris™ (Smooth-On) matched the compliance range of the numerical and in vivo patient models most closely out of the tested silicone materials. Our approach is promising for vascular applications where mechanical compliance is especially important, such as the study of diseases which commonly affect arterial wall stiffness, such as atherosclerosis, and the model-based design, surgical training, and optimisation of vascular prostheses.

Fluid-Structure Interaction Within Models of Patient-Specific Arteries: Computational Simulations and Experimental Validations.

Cardiovascular disease (CVD) is the leading cause of mortality worldwide and its incidence is rising due to an aging population. The development and progression of CVD is directly linked to adverse vascular hemodynamics and biomechanics, whose in-vivo measurement remains challenging but can be simulated numerically and experimentally. The ability to evaluate these parameters in patient-specific CVD cases is crucial to better predict future disease progression, risk of adverse events, and treatment efficacy. While significant progress has been made toward patient-specific hemodynamic simulations, blood vessels are often assumed to be rigid, which does not consider the compliant mechanical properties of vessels whose malfunction is implicated in disease. In an effort to simulate the biomechanics of flexible vessels, fluid-structure interaction (FSI) simulations have emerged as promising tools for the characterization of hemodynamics within patient-specific cardiovascular anatomies. Since FSI simulations combine the blood's fluid domain with the arterial structural domain, they pose novel challenges for their experimental validation. This paper reviews the scientific work related to FSI simulations for patient-specific arterial geometries and the current standard of FSI model validation including the use of compliant arterial phantoms, which offer novel potential for the experimental validation of FSI results.

Thymic carcinoma with Lynch syndrome or microsatellite instability, a rare entity responsive to immunotherapy.

IMPORTANCE: Thymic carcinoma (TC) is a rare aggressive tumour occurring in adults characterised by one of the lowest tumor mutational burdens (TMB). Microsatellite instability (MSI) is a mutational signature, caused by defects in the DNA MisMatch Repair (MMR) system, that predicts benefit from immunotherapy and causes high TMB. Fragmentary and unstructured evidence of these conditions co-occurring are reported in literature. OBJECTIVE: Review available data on the co-occurrence of these two conditions and determine its frequency in our institute case series. DESIGN: We performed a systematic analysis of literature and a retrospective evaluation of all the cases of TET treated at our institution from 2000 to 2020, selecting patients with a medical history of multiple tumours to enhance a priori probability of identifying cases with underlying predisposition. RESULTS: Literature yielded 3 cases of patients with MSI TC, for which MMR gene alteration was reported. None of them received immunotherapy. Of 366 patients with TETs treated in our institute, 32 had a medical history of multiple tumours and 25 of 32 (19 thymomas and 6 TCs) had available tissue for MMR analysis. One patient with TC showed a high TMB, and MSI due to MLH1 mutation and was treated in a phase II study with avelumab and axitinib combination obtaining a long-lasting partial response. MLH1 alterations are shared across MSI TC cases. CONCLUSIONS AND RELEVANCE: This analysis highlights the usefulness of MSI testing in patients with TC. The observation of cases of TC occurring in patients with Lynch syndrome and the unexpected homogeneity of gene alterations support further investigation.

Vulval hidradenoma papilliferum: a clinical and dermoscopic study.

Hidradenoma papilliferum (HP) is a rare, slow-growing, benign adnexal tumour with apocrine differentiation. It usually affects the anogenital region in adult women and is clinically polymorphous, mimicking other benign or malignant neoformations. The dermoscopic features of vulval HP have not been reported yet. We report the clinical and dermoscopic features in a case series of histopathologically proven vulval HPs. Dermoscopy may be a useful tool for the diagnosis of vulval HP. To our knowledge, our paper represents the first report of dermoscopic findings in a series of vulval HPs in a multiracial population.

Thin vulvar melanoma: a challenging diagnosis. Dermoscopic features of a case series.

BACKGROUND: Vulvar melanoma (VM) is rare and is often diagnosed late. Dermoscopy may aid in its recognition, differentiating VM from other more common vulvar lesions, such as melanosis and naevi. However, little is known about the dermoscopic features of thin VM. AIM: To retrospectively analyse a series of histopathologically diagnosed thin VMs and to highlight their most suggestive dermoscopic features. METHODS: A multicentre, retrospective study was conducted, including histopathologically proven thin VMs, either intraepidermal or with Breslow thickness ≤ 0.5 mm, diagnosed during the period 2016-2018. We particularly focused on their dermoscopic characteristics to highlight the most suggestive dermoscopic diagnostic clues. RESULTS: In total, 14 cases of early-stage VM were included, in women with a mean age at diagnosis of 64.86 years. The most frequently affected sites were the labia minora. Of these, 11 cases were unifocal. Dermoscopy most often revealed structureless areas, grey globules and areas, irregular black-brown dots, blue and white structures, and red areas. CONCLUSIONS: In our experience, early-stage VM often exhibits dermoscopic features that are more typical of thicker cutaneous melanomas. Dermoscopy may provide useful clues for the prompt diagnosis of thin VM.

Computational study of aortic hemodynamics for patients with an abnormal aortic valve: The importance of secondary flow at the ascending aorta inlet.

Blood flow in the aorta is helical, but most computational studies ignore the presence of secondary flow components at the ascending aorta (AAo) inlet. The aim of this study is to ascertain the importance of inlet boundary conditions (BCs) in computational analysis of flow patterns in the thoracic aorta based on patient-specific images, with a particular focus on patients with an abnormal aortic valve. Two cases were studied: one presenting a severe aortic valve stenosis and the other with a mechanical valve. For both aorta models, three inlet BCs were compared; these included the flat profile and 1D through-plane velocity and 3D phase-contrast magnetic resonance imaging derived velocity profiles, with the latter being used for benchmarking. Our results showed that peak and mean velocities at the proximal end of the ascending aorta were underestimated by up to 41% when the secondary flow components were neglected. The results for helical flow descriptors highlighted the strong influence of secondary velocities on the helical flow structure in the AAo. Differences in all wall shear stress (WSS)-derived indices were much more pronounced in the AAo and aortic arch (AA) than in the descending aorta (DAo). Overall, this study demonstrates that using 3D velocity profiles as inlet BC is essential for patient-specific analysis of hemodynamics and WSS in the AAo and AA in the presence of an abnormal aortic valve. However, predicted flow in the DAo is less sensitive to the secondary velocities imposed at the inlet; hence, the 1D through-plane profile could be a sufficient inlet BC for studies focusing on distal regions of the thoracic aorta.

On the choice of outlet boundary conditions for patient-specific analysis of aortic flow using computational fluid dynamics.

Boundary conditions (BCs) are an essential part in computational fluid dynamics (CFD) simulations of blood flow in large arteries. Although several studies have investigated the influence of BCs on predicted flow patterns and hemodynamic wall parameters in various arterial models, there is a lack of comprehensive assessment of outlet BCs for patient-specific analysis of aortic flow. In this study, five different sets of outlet BCs were tested and compared using a subject-specific model of a normal aorta. Phase-contrast magnetic resonance imaging (PC-MRI) was performed on the same subject and velocity profiles extracted from the in vivo measurements were used as the inlet boundary condition. Computational results obtained with different outlet BCs were assessed in terms of their agreement with the PC-MRI velocity data and key hemodynamic parameters, such as pressure and flow waveforms and wall shear stress related indices. Our results showed that the best overall performance was achieved by using a well-tuned three-element Windkessel model at all model outlets, which not only gave a good agreement with in vivo flow data, but also produced physiological pressure waveforms and values. On the other hand, opening outlet BCs with zero pressure at multiple outlets failed to reproduce any physiologically relevant flow and pressure features.

Towards the improved quantification of in vivo abnormal wall shear stresses in BAV-affected patients from 4D-flow imaging: Benchmarking and application to real data.

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.

The risk of preeclampsia beyond the first pregnancy among women with type 1 diabetes parity and preeclampsia in type 1 diabetes.

AIM: To estimate the incidence of preeclampsia (PE) among nulliparous and multiparous patients with type 1 diabetes and to study predictors of PE. METHODS: We prospectively collected data on all pregnancies of patients with pregestational type 1 diabetes, followed at our Prenatal Medicine Unit between 1993 and 2008. Medical records were prospectively reviewed by two obstetricians for maternal demographics, pregnancy data, maternal and fetal outcomes. Data were analyzed according to the development of PE and parity. RESULTS: We identified and collected data on 291 eligible pregnancies (195 among nulliparae and 96 among multiparae). The incidence of PE was 9.2% (95% CI: 5.6-14.2) among nulliparae and 9.4% (95% CI: 4.4-17.0) among multiparae. Patients who developed PE had higher HbA1c during pregnancy compared to patients who did not (p=0.026 among nulliparae and p=0.032 among multiparae). Chronic hypertension [OR 17.12 (3.22, 91.00)], microalbuminuria at the beginning of the pregnancy [OR 3.77 (1.22, 11.61)], weight gain during pregnancy [OR 1.13 (1.04, 1.23)] and HbA1c in the first trimester [2.81 (1.12, 7.05)], but not parity, were significant predictors of PE. CONCLUSIONS: Among patients with type 1 diabetes the incidence of PE was similar among nulliparae and multiparae, unlikely in the general population where PE is a disease of the first pregnancy. An increased risk of PE should be assumed for both nulliparous and multiparous women with pregestational diabetes.