Fluid-Structure Interaction in Coronary Stents: A Discrete Multiphysics Approach

Commentaries on Viewpoint: The human cutaneous circulation as a model of generalized microvascular function

This study investigates the unsteady hydrodynamic behavior of water interacting with a single horizontal row of barriers in an idealized channel, considering barrier porosity (0.3≤ϕ≤1) and channel slope (0°≤θ≤45°). Using computational fluid dynamics (CFD), fluid–structure interactions are simulated under extreme conditions representative of floods and tsunamis, enabling assessment of barrier performance in mitigating flow impact. The numerical framework captures the evolution of the water interface and flow redirection as the fluid navigates barriers of varying porosity and slope. Pressure and shear forces acting on both the barriers and downstream wall are quantified, and a bivariate polynomial correlation is developed to express these forces continuously as functions of ϕ and θ, facilitating interpolation across the parameter space. Results indicate that increasing porosity generally amplifies both pressure and shear forces, with the most significant pressure jumps occurring between ϕ=0.3–0.4 and ϕ=0.9–1. Pressure forces consistently exceed shear forces. Increasing the slope from 0° to 45° raises pressure forces by nearly fivefold and shear forces by roughly threefold, while flood front run-up and arrival time remain largely unaffected. Furthermore, adding more barriers, particularly at lower porosities, steadily increases the forces experienced. These findings reveal the non-linear interplay between porosity, slope, and barrier arrangement on hydrodynamic loads, providing critical guidance for designing and optimizing barriers in flood mitigation and coastal protection applications.

Stent deformation: an experimental study of coronary ostial stenting

We discuss entrainment phenomena in the regulation of cerebral and peripheral blood flow in newborn rats under normal conditions and during pathological changes in the dynamics of blood vessels accompanying the development of stroke. Using a wavelet-based coherence measure, we analyze the degree of interrelation between the dynamics of blood flow in the sagittal sinus, the surrounding network of small vessels, as well as in the artery and vein of the neck. We show that the coherence measure reflects changes in the entrainment at the latent stage of stroke formation.

We propose a mesh-free and discrete (particle-based) multi-physics approach for modelling the hydrodynamics in flexible biological valves. In the first part of this study, the method is successfully validated against both traditional modelling techniques and experimental data. In the second part, it is further developed to account for the formation of solid aggregates in the flow and at the membrane surface. Simulations of various types of aggregates highlight the main benefits of discrete multi-physics and indicate the potential of this approach for coupling the hydrodynamics with phenomena such as clotting and calcification in biological valves.

Protruding coronary artery stents can adversely affect transcatheter aortic valve replacement (TAVR) procedure. Current evidence on the topic is limited. We aim to study the clinical feasibility and safety of flaring of protruding coronary artery stents before TAVR to reduce interaction with transcatheter heart valves. Twenty consecutive patients with 22 protruding coronary stents were optimized with a dual-diameter balloon before TAVR. Procedural success, stent and valve geometry on angiogram, periprocedural and subsequent clinical outcomes as well as valve hemodynamics on echocardiography were evaluated. Procedural success was achieved in 100% of coronary procedure and TAVR without any major complication directly related to the flaring of stents. There was no coronary artery obstruction after TAVR or visible stent or valve deformity. All valves had normal hemodynamics immediately post-deployment with none having clinically significant aortic insufficiency. One patient had inpatient mortality unrelated to coronary stent optimization. One valve had hemodynamic valve degeneration on follow-up which was unrelated to coronary stent flaring and the patient was asymptomatic. Flaring of protruding coronary stents before TAVR is technically feasible and safe and can potentially minimize stent-valve interaction for during of after TAVR.

In recent years, computational simulations have emerged as valuable tools for the evaluation of atherosclerosis progression in coronary anatomies, although only a few studies have utilized more realistic Fluid-Structure Interaction (FSI) simulations. This work aims to compare the results of Computational Fluid Dynamics (CFD), Structural Finite Element Analysis (structural FEA) and FSI simulations in order to assess differences in plaque progression indices estimation. We performed structural FEA, CFD and FSI on five patient-specific epicardial coronary anatomies using the commercial software LS-Dyna. To account for the vessel pre-stress, the zero-pressure configuration was calculated for each anatomy with an inverse elastostatic algorithm. CFD, structural FEA and FSI simulations were performed applying boundary conditions based on physiological values. The comparison between structural FEA and FSI showed similar stress distribution and vessel expansions, with differences found only in the distal parts of the coronaries, where pressure reduction due to pressure loss affects the vessel walls. The elastic walls of the coronaries impact blood flow, resulting in a more disturbed flow. However, time averaged wall shear stress (TAWSS) and oscillatory shear index (OSI) distributions are similar across each coronary between CFD and FSI; TAWSS is slightly higher in CFD while OSI peaks are higher in FSI. In conclusion, given the significantly higher computational costs of FSI, we believe that CFD and structural FEA offer a more practical and cost-effective approach, providing results comparable to those of FSI, making them preferable options.

In silico modelling of aortic annuloplasty: hemodynamic assessment through in vitro experiments and in vivo MRI.

Hemodynamics and thermal characteristics of a deformable stenosed carotid artery with heat generation: Effect of heart rate, stenotic severity, and wall elasticity

The comparison of cerebral circulation impairment in humans and horses provides important insights into the dynamics of blood flow in the brain across different species, connecting veterinary and human medicine. This analysis brings together findings from various studies to highlight the similarities in anatomy and physiology between humans and horses, which can improve our understanding of cerebrovascular health. Research emphasizes the importance of maintaining stable cerebral blood flow to prevent damage from lack of oxygen, which is essential for the brain’s metabolism in both humans and horses. Studies on the factors affecting overall blood flow in the body reveal strong connections between cardiovascular health and blood flow to the brain, showing how baroreflex sensitivity and blood pressure play a role in maintaining brain function. Understanding the reactivity of blood vessels in the brain is associated with neurological disorders, emphasizing the need for non-invasive evaluation techniques that can be used for both humans and horses. Research on the coupling of nerve and blood vessel activity further explains how blood flow is regulated during brain activity, highlighting potential weaknesses under unhealthy conditions. While the role of exercise in promoting cerebrovascular health is recognized, there are still gaps in our knowledge of its effects on the brain, especially in horses. Advanced imaging techniques like MRI are presented as essential tools for assessing the health of small blood vessels and blood flow in the brain, offering potential applications in the early detection and treatment of cerebrovascular diseases. By comparing the dynamics of blood flow in the brain in humans and horses, this review not only increases our understanding but also suggests a more integrated approach to diagnosis and treatment, improving practices in both fields. These insights emphasize the common principles and specific differences in cerebrovascular health in different species, and support the need for collaborative research in veterinary and human medicine.

Calcific aortic valve disease (CAVD) arises from coupled interactions between blood flow, tissue mechanics, and cellular signaling. Hemodynamic forces influence endothelial and interstitial cell behavior, while the resulting tissue remodeling alters valve motion and flow patterns. Capturing this two-way feedback requires models that integrate fluid-structure mechanics with biochemical regulation, yet such multiscale coupling remains technically challenging. Previous computational models have focused on isolated aspects of the disease: fluid-structure interaction (FSI) simulations reproduce valve deformation and flow, and systems biology (SB) models describe molecular signaling that drives fibrosis and calcification. However, without coupling, these approaches cannot predict how mechanical dysfunction initiates biochemical remodeling or how biochemical changes feed back on mechanics. Here, we present a multi-physics computational framework that couples three-dimensional FSI simulations of aortic valve dynamics with a mechanistic SB model of calcification signaling. The FSI module resolves pulsatile blood flow and leaflet deformation, yielding local wall shear stresses and tissue strains throughout the cardiac cycle. These mechanical quantities are used as inputs to the SB module, which represents key biochemical pathways governing inflammation, TGF- β /SMAD signaling, and nitric-oxide (NO)-mediated inhibition within valvular cells. Simulations predict long-term calcification trajectories for valves of varying thickness, showing that fibrosis-induced stiffening lowers shear stress, reduces NO synthesis, and enhances TGF- β activation, thereby accelerating calcification. The framework is modular and extensible, allowing future incorporation of additional pathways, as well as implementation of full two-way coupling between the FSI and SB models. By integrating physics-based hemodynamics with systems-level biochemistry, this study provides a proof-of-principle demonstration of a next-generation, multi-scale modeling platform for studying cardiovascular disease that unites blood flow dynamics and biochemical signaling.

3D-printed carbonate apatite scaffolds inspired by cuttlebone biomechanics and blood flow dynamics for layer-by-layer collapse and spatial bone formation.

Assessing the risk of rupture is extremely important to reduce the mortality of the abdominal aortic aneurysm (AAA). Current clinical guidelines suggest considering the maximum diameter as a criterion for planning and surgical intervention; however, this approach is too simplistic and overlooks other morphological parameters that are associated with the risk of rupture. The aim of this paper is to study the thrombogenicity and to predict the risk of AAA rupture by taking into consideration the geometrical asymmetry of the aneurysm, studying its effect on blood flow behaviour and vortical structure, spatiotemporal distribution of wall shear stresses (WSS), and their related parameters. To show the effect of asymmetry on blood flow dynamics and hemodynamic forces, five virtual models were constructed using five values of geometrical asymmetry ratio β ranging from β=0.2 (asymmetric model; AM) to β=1 (symmetric model; SM). Simulations were run for each geometry under transient physiological flow conditions using finite volume discretization. Resting flow rate was investigated in these models and our results demonstrate that the asymmetry of the aneurysm has a clear effect on the flow behaviour, and consequently on WSS distribution, oscillatory shear index (OSI) and time averaged wall shear stress (TAWSS). Furthermore, these preliminary findings suggest that thrombus formation and rupture risk are more probable in an asymmetric abdominal aortic aneurysm.

The hypothesis that the rate of increase in muscle O2 uptake (VO2mus) at the onset of exercise is influenced by muscle blood flow was tested during forearm exercise with the arm either above or below heart level to modify perfusion pressure. Ten young men exercised at a power of approximately 2.2 W, and five of these subjects also worked at 1.4 W. Blood flow to the forearm was calculated from the product of blood velocity and cross-sectional area obtained with Doppler techniques. Venous blood was sampled from a deep forearm vein to determine O2 extraction. The rate of increase in VO2mus and blood flow was assessed from the mean response time (MRT), which is the time to achieve approximately 63% increase from baseline to steady state. In the arm below heart position during the 2.2-W exercise, blood flow and VO2mus both increased, with a MRT of approximately 30 s. With the arm above the heart at this power, the MRTs for blood flow [79.8 +/- 15.7 (SE)s] and VO2mus (50.2 +/- 4.0 s) were both significantly slower. Consistent with these findings were the greater increases in venous plasma lactate concentration over resting valued in the above heart position (2.8 +/- 0.4 mmol/l) than in the below heart position (0.9 +/- mmol/l). At the lower power, both blood flow and VO2mus also increased more rapidly with the arm below compared with above the heart. These data support the hypothesis that changes in blood flow at the onset of exercise have a direct effect on oxidative metabolism through alterations in O2 transport.

A comparative application of major dynamic light scattering (DLS)‐based image methodologies applied to transcranial cerebral blood flow imaging is presented. In particular, the study delves into assessing capability of Laser Doppler Flowmetry (LDF), Laser Speckle Contrast Imaging (LSCI), and Diffuse Correlation Spectroscopy (DCS) in enhancing the spatial and temporal resolution of transcranial blood flow imaging. An integral part of the study is focused on the modulation of blood flow through the administration of the vasodilator drug, Sodium Nitroprusside (SNP). This pharmacological intervention facilitated a direct observation of cerebral vasculature's responsiveness to external stimuli, illuminating the physiological adaptations within the brain's microvascular architecture. Advanced LSCI processing techniques are incorporated, notably entropy and principal component analysis (PCA). Entropy is providing a quantifiable measure of the randomness and complexity within the speckle patterns of transcranial blood flow images, revealing remarkably similar outcomes with DSC approach in terms of blood flow dynamics and its quantitative evaluation. The application of PCA approach is provided a more nuanced understanding of blood flow dynamics, facilitating the identification of subtle changes induced by drug administration. This method proved instrumental in enhancing the visualization and detection of nuanced blood flow dynamics, thereby allowing for a more detailed examination of cerebral circulation alterations induced by SNP administration. The study seeks to offer a wider‐ranging insight into comprehending the translating further the concept of DLS into transcrainial blood flow vizualization and explore its practical applications, considering hardware, advanced quantitative image processing, and data acquisition.