Influence of vascular geometry on local hemodynamic parameters: phantom and small rodent study

The Stress Phase Angle Measurement Using Spectral Domain Optical Coherence Tomography

The stress phase angle (SPA), defined as the temporal phase angle between circumferential stress (CS) in the arterial wall and wall shear stress (WSS), is utilized to investigate the interactions between CS and WSS. SPA serves as an important parameter for the early diagnosis of cardiovascular disease. In this study, we proposed a novel method for measuring SPA using spectral domain optical coherence tomography (SD-OCT). The multi-M-mode scan strategy is adopted for interference spectrum acquisition. The phases of CS and WSS are extracted from the corresponding structural and flow velocity images of SD-OCT. The method is validated by measuring SPA in the outflow tract (OFT) of chick embryonic hearts and the common carotid artery of mice. To the best of our knowledge, this is the first time that OCT has been used for SPA measurement.

Arteriographic patterns of peripheral arterial disease in lower limbs in a Peruvian cohort of patients

INTRODUCTION

There is currently no universal and uniform pattern of peripheral arterial disease (PAD) in the lower limbs; however, it is influenced by various cardiovascular factors of the individual. The objective of this study was to identify the arteriographic patterns of PAD in the lower limbs according to cardiovascular factors in a Peruvian cohort of patients.

METHODS

This is an analytical, observational, and retrospective study. The arteriographic patterns of PAD in the aortoiliac segment were analyzed with the TransAtlantic InterSociety Consensus (TASC-II) score and the Global Anatomic Staging System (GLASS) for the femoropopliteal (FP), infraopopliteal (IP), and pedial (P) segments in a Peruvian cohort from January 2018 to May 2021.

RESULTS

595 patients (833 extremities) were analyzed with a mean age of 67.54 ± 16.39 years, and the main cardiovascular factor was diabetes (65.04%). The patients older than 65 years with GLASS FP 4 (p = 0.042), IP 0 (p = 0.004), and P2 (p = 0.047) presented significant findings: in men and women with GLASS IP 4 (p = 0.031) and P 2 (p = 0.045); diabetes with TASC-II A (p = 0.031), GLASS FP 4 (p = 0.038), IP 4 (p = 0.009), and P2 (p = 0.003); dyslipidemia with TASC-II D (p = 0.027), GLASS FP 4 (p = 0.038), IP 0 (p = 0.009), and P0 (p = 0.003); smoking with TASC-II D (p = 0.001), GLASS FP 4 (p = 0.049) and IP 0 (p = 0.008); chronic coronary disease with GLASS IP 4 (p = 0.049) and P2 (p = 0.037); chronic kidney disease with GLASS FP 4 (p=0.047), IP 4 (p = 0.004), and P2 (p = 0.016); and previous amputation history with GLASS IP 4 (p = 0.015) and P2 (p = 0.039). The most frequent arteriographic pattern of PAD in the lower limbs of our cohort was TASC-II A, GLASS FP 0 and 4, IP 0, and P2 (p = 0.047).

CONCLUSION

Our work will allow the limb salvage teams to understand the behavior of PAD affectation in the population of our environment, allowing a timely control of cardiovascular risk factors, adequate revascularization planning, and a significant reduction in the risk of loss of limb.

Age- and gender-dependent variability in the geometry of middle cerebral artery bifurcations

The goal of this study was to analyze trends in the geometric parameters of blood vessels with age in a randomly selected group of 200 computed tomography angiography studies of radiologically healthy individuals using dedicated statistical techniques. A quantitative description of cerebral vascular geometry with numerical parameters (bifurcation angle, branching angle, co-planarity index, average curvature, and average torsion) was proposed. The changes and variability in geometry were analyzed according to age. The bifurcation angle, branching angle, and average curvature increased with age, whereas the co-planarity index and average torsion decreased with age. For equal-diameter branches, women comparing to men presented lower bifurcation angles in the 4th decade of life, and lower values for the co-planarity index in the 3rd and 4th decades of life. In non-equal-diameter branches, the opposite relationship was observed for bifurcation angle in the 4th decade of life comparing both groups. All analyzed parameters showed clearly visible trends with patient age. Deviations in specific decades of life were detected; these deviations could be linked to the development of aneurysms in specific age groups.

Composable microfluidic spinning platforms for facile production of biomimetic perfusable hydrogel microtubes

Microtissues with specific structures and integrated vessels play a key role in maintaining organ functions. To recapitulate the in vivo environment for tissue engineering and organ-on-a-chip purposes, it is essential to develop perfusable biomimetic microscaffolds. We developed facile all-aqueous microfluidic approaches for producing perfusable hydrogel microtubes with diverse biomimetic sizes and shapes. Here, we provide a detailed protocol describing the construction of the microtube spinning platforms, the assembly of microfluidic devices, and the fabrication and characterization of various perfusable hydrogel microtubes. The hydrogel microtubes can be continuously generated from microfluidic devices due to the crosslinking of alginate by calcium in the coaxial flows and collecting bath. Owing to the mild all-aqueous spinning process, cells can be loaded into the alginate prepolymer for microtube spinning, which enables the direct production of cell-laden hydrogel microtubes. By manipulating the fluid dynamics at the microscale, the composable microfluidic devices and platforms can be used for the facile generation of six types of biomimetic perfusable microtubes. The microfluidic platforms and devices can be set up within 3 h from commonly available and inexpensive materials. After 10-20 min required to adjust the platform and fluids, perfusable hydrogel microtubes can be generated continuously. We describe how to characterize the microtubes using scanning electron or confocal microscopy. As an example application, we describe how the microtubes can be used for the preparation of a vascular lumen and how to perform barrier permeability tests of the vascular lumen.

A Systematic Review for the Design of In Vitro Flow Studies of the Carotid Artery Bifurcation

PURPOSE

In vitro blood flow studies in carotid artery bifurcation models may contribute to understanding the influence of hemodynamics on carotid artery disease. However, the design of in vitro blood flow studies involves many steps and selection of imaging techniques, model materials, model design, and flow visualization parameters. Therefore, an overview of the possibilities and guidance for the design process is beneficial for researchers with less experience in flow studies.

METHODS

A systematic search to in vitro flow studies in carotid artery bifurcation models aiming at quantification and detailed flow visualization of blood flow dynamics results in inclusion of 42 articles.

RESULTS

Four categories of imaging techniques are distinguished: MRI, optical particle image velocimetry (PIV), ultrasound and miscellaneous techniques. Parameters for flow visualization are categorized into velocity, flow, shear-related, turbulent/disordered flow and other parameters. Model materials and design characteristics vary between study type.

CONCLUSIONS

A simplified three-step design process is proposed for better fitting and adequate match with the pertinent research question at hand and as guidance for less experienced flow study researchers. The three consecutive selection steps are: flow parameters, image modality, and model materials and designs. Model materials depend on the chosen imaging technique, whereas choice of flow parameters is independent from imaging technique and is therefore only determined by the goal of the study.

Semi-automatic measurements and description of the geometry of vascular tree based on Bézier spline curves: application to cerebral arteries

Background

The geometry of the vessels is easy to assess in novel 3D studies. It has significant influence on flow patterns and this way the evolution of vascular pathologies such as aneurysms and atherosclerosis. It is essential to develop robust system for vascular anatomy measurement and digital description allowing for assessment of big numbers of vessels.

Methods

A semiautomatic, robust, integrated method for vascular anatomy measurements and mathematical description are presented. Bezier splines of 6th degree and continuity of C3 was proposed and distribution of control points was dependent on local radius. Due to main interest of our institution, the system was primarily used for the assessment of the geometry of the intracranial arteries, especially the first Medial Cerebral Artery division.

Results

1359 synthetic figures were generated: 381 torus and 978 spirals. Experimental verification of the proposed methodology was conducted on 400 Middle Cerebral Artery divisions.

Conclusions

In difference to other described solution all proposed methodology steps were integrated allows analysis of variability of geometrical parameters among big number of Medial Cerebral Artery bifurcations using single application. This allows for determination of significant trends in the parameters variability with age and in contrary almost no differences between men and women.