Morphometric Reconstruction of Coronary Vasculature Incorporating Uniformity of Flow Dispersion

Experimental limitations in measurements of coronary flow in the beating heart have led to the development of in silico models of reconstructed coronary trees. Previous coronary reconstructions relied primarily on anatomical data, including statistical morphometry (e.g., diameters, length, connectivity, longitudinal position). Such reconstructions are non-unique, however, often leading to unrealistic predicted flow features. Thus, it is necessary to impose physiological flow constraints to ensure realistic tree reconstruction. Since a vessel flow depends on its diameter to fourth power, diameters are the logical candidates to guide vascular reconstructions to achieve realistic flows. Here, a diameter assignment method was developed where each vessel diameter was determined depending on its downstream tree size, aimed to reduce flow dispersion to within measured range. Since the coronary micro-vessels are responsible for a major portion of the flow resistance, the auto regulated coronary flow was analyzed in a morphometry-based reconstructed 400 vessel arterial microvascular sub-tree spanning vessel orders 1–6. Diameters in this subtree were re-assigned based on the flow criteria. The results revealed that diameter re-assignment, while adhering to measured morphometry, significantly reduced the flow dispersion to realistic levels while adhering to measured morphometry. The resulting network flow has longitudinal pressure distribution, flow fractal nature, and near-neighboring flow autocorrelation, which agree with measured coronary flow characteristics. Collectively, these results suggest that a realistic coronary tree reconstruction should impose not only morphometric data but also flow considerations. The work is of broad significance in providing a novel computational framework in the field of coronary microcirculation. It is essential for the study of coronary circulation by model simulation, based on a realistic network structure

Biaxial deformation of collagen and elastin fibers in coronary adventitia

The microstructural deformation-mechanical loading relation of the blood vessel wall is essential for understanding the overall mechanical behavior of vascular tissue in health and disease. We employed simultaneous mechanical loading-imaging to quantify in situ deformation of individual collagen and elastin fibers on unstained fresh porcine coronary adventitia under a combination of vessel inflation and axial extension loading. Specifically, the specimens were imaged under biaxial loads to study microscopic deformation-loading behavior of fibers in conjunction with morphometric measurements at the zero-stress state. Collagen fibers largely orientate in the longitudinal direction, while elastin fibers have major orientation parallel to collagen, but with additional orientation angles in each sublayer of the adventitia. With an increase of biaxial load, collagen fibers were uniformly stretched to the loading direction, while elastin fibers gradually formed a network in sublayers, which strongly depended on the initial arrangement. The waviness of collagen decreased more rapidly at a circumferential stretch ratio of λθ = 1.0 than at λθ = 1.5, while most collagen became straightened at λθ = 1.8. These microscopic deformations imply that the longitudinally stiffer adventitia is a direct result of initial fiber alignment, and the overall mechanical behavior of the tissue is highly dependent on the corresponding microscopic deformation of fibers. The microstructural deformation-loading relation will serve as a foundation for micromechanical models of the vessel wall

Assessing teamwork competence

Abstract. Background: In recent years, organizations of all types have undergone major changes, and teamwork is one of them. This way of working generates greater profits for an organization. This article aims to assess the teamwork competence of the employees of various Spanish companies in order to determine how effective the team members are in their professional actions. Method: We contacted 55 teams from different organizations and obtained a non-probabilistic sample comprised of 55 participants (subjects tested) and 218 observers (evaluators: coordinators and co-workers). The instrument used for data collection was the Teamwork Rubric (Torrelles, 2011) and data analysis was based on 360º feedback. Results: 80% of the teams analyzed obtained median scores for teamwork competence that were greater than 3, whereas 20% obtained scores between 2 and 3. Conclusions: The results showed that the workers in the companies studied had not fully acquired teamwork competence. It is necessary to find training solutions to improve their level of acquisition, particularly the dimensions of performance and regulation. Resumen: Evaluación de la competencia de trabajo en equipo. Antecedentes: En los últimos años las organizaciones han experimentado múltiples cambios y el trabajo en equipo es uno de ellos. Esta manera de trabajar genera más beneficio en las organizaciones. El presente artículo tiene como objetivo evaluar la competencia de trabajo en equipo de los empleados de diferentes empresas españolas para conocer las debilidades y potencialidades de los equipos en su acción profesional. Método: Se ha contactado con 55 equipos procedentes de diferentes organizaciones configurando así una muestra de carácter no probabilístico formada por 55 participantes (sujetos evaluados) y 218 observadores (sujetos evaluadores: coordinadores y compañeros de trabajo). El instrumento de recogida de los datos es la Rúbrica de Trabajo en Equipo (Torrelles, 2011) y su aplicación se ejecuta a través del método de evaluación 360º. Resultados: El 80% de los trabajadores muestran que tienen una media de 3 o superior en el nivel de adquisición de la competencia de trabajo en equipo, el 20% restante se encuentran entre 2 y 3. Conclusiones: Los resultados muestran que los trabajadores de las empresas españolas no tienen adquirida la competencia de trabajo en equipo en toda su globalidad, pues dimensiones como la regulación y la ejecución necesitan ser mejoradas

Mechanisms of myocardium-coronary vessel interaction

The mechanisms by which the contracting myocardium exerts extravascular forces (intramyocardial pressure, IMP) on coronary blood vessels and by which it affects the coronary flow remain incompletely understood. Several myocardium-vessel interaction (MVI) mechanisms have been proposed, but none can account for all the major flow features. In the present study, we hypothesized that only a specific combination of MVI mechanisms can account for all observed coronary flow features. Three basic interaction mechanisms (time-varying elasticity, myocardial shortening-induced intracellular pressure, and ventricular cavity-induced extracellular pressure) and their combinations were analyzed based on physical principles (conservation of mass and force equilibrium) in a realistic data-based vascular network. Mechanical properties of both vessel wall and myocardium were coupled through stress analysis to simulate the response of vessels to internal blood pressure and external (myocardial) mechanical loading. Predictions of transmural dynamic vascular pressure, diameter, and flow velocity were determined under each MVI mechanism and compared with reported data. The results show that none of the three basic mechanisms alone can account for the measured data. Only the combined effect of the cavity-induced extracellular pressure and the shortening-induced intramyocyte pressure provides good agreement with the majority of measurements. These findings have important implications for elucidating the physical basis of IMP and for understanding coronary phasic flow and coronary artery and microcirculatory disease