Stenosis Geometry Research Articles

Prediction of Hemodynamic-Related Hemolysis in Carotid Stenosis and Aiding in Treatment Planning and Risk Stratification Using Computational Fluid Dynamics.

Atherosclerosis affects human health in many ways, leading to disability or premature death due to ischemic heart disease, stroke, or limb ischemia. Poststenotic blood flow disruption may also play an essential role in artery wall impairment linked with hemolysis related to shear stress. The maximum shear stress in the atherosclerotic plaque area is the main parameter determining hemolysis risk. In our work, a 3D internal carotid artery model was built from CT scans performed on patients qualified for percutaneous angioplasty due to its symptomatic stenosis. The obtained stenosis geometries were used to conduct a series of computer simulations to identify critical parameters corresponding to the increase in shear stress in the arteries. Stenosis shape parameters responsible for the increase in shear stress were determined. The effect of changes in the carotid artery size, length, and degree of narrowing on the change in maximum shear stress was demonstrated. Then, a correlation for the quick initial diagnosis of atherosclerotic stenoses regarding the risk of hemolysis was developed. The developed relationship for rapid hemolysis risk assessment uses information from typical non-invasive tests for treated patients. Practical guidelines have been developed regarding which stenosis shape parameters pose a risk of hemolysis, which may be adapted in medical practice.

Generation of synthetic aortic valve stenosis geometries for in silico trials.

In silico trials are a promising way to increase the efficiency of the development, and the time to market of cardiovascular implantable devices. The development of transcatheter aortic valve implantation (TAVI) devices, could benefit from in silico trials to overcome frequently occurring complications such as paravalvular leakage and conduction problems. To be able to perform in silico TAVI trials virtual cohorts of TAVI patients are required. In a virtual cohort, individual patients are represented by computer models that usually require patient-specific aortic valve geometries. This study aimed to develop a virtual cohort generator that generates anatomically plausible, synthetic aortic valve stenosis geometries for in silico TAVI trials and allows for the selection of specific anatomical features that influence the occurrence of complications. To build the generator, a combination of non-parametrical statistical shape modeling and sampling from a copula distribution was used. The developed virtual cohort generator successfully generated synthetic aortic valve stenosis geometries that are comparable with a real cohort, and therefore, are considered as being anatomically plausible. Furthermore, we were able to select specific anatomical features with a sensitivity of around 90%. The virtual cohort generator has the potential to be used by TAVI manufacturers to test their devices. Future work will involve including calcifications to the synthetic geometries, and applying high-fidelity fluid-structure-interaction models to perform in silico trials.

Blood Flow with Heat Transfer through Different Geometries of Stenotic Arteries

The current study evaluates blood flow patterns in symmetrical, elliptical, trapezoidal, triangular, cosine-shaped and bell-shaped stenosed arteries with heat transfer. The ordinary differential equations obtained from the transformation applicable to the controlling partial differential equations. The system of ordinary differential equations has been solved using analytical methods of variation of parameters with the help of software. The MATLAB code graphically demonstrates various profiles and analyses the impact of the Prandtl number, magnetic field, Darcy number and Radiation number on velocity, wall shear stress, temperature and volumetric flow rate. The preponderance of blood flow problems is caused by stenosis between z = 1 and z = 2 locations for symmetrical, elliptical, trapezoidal, triangular, cosine-shaped and bell-shaped stenosis. The originality of the present study is the simultaneous influence of varied stenosis geometries on heat transfer. The main observation of blood velocity is that it is also greater for bell-shaped artery walls in the presence of a magnetic field than for trapezoidal artery walls between z = 1 and z = 2 and all other geometries in between. It may help to understand the blood flow in stenosed blood arteries caused by cardiovascular disease. HIGHLIGHTS The current study evaluates blood flow patterns in symmetrical, elliptical, trapezoidal, triangular, cosine-shaped and bell-shaped stenosed arteries with heat transfer The effect of magnetic field and Darcy number on a diseased segment of an artery is examined Due to the presence of hemoglobin in RBCs, which contains iron oxide particles and is capable of binding oxygen molecules, the blood is greatly impacted by the magnetic field GRAPHICAL ABSTRACT

Numerical simulation of the cavopulmonary connection flow with conduit stenoses of varying configurations

The circulation in the total cavopulmonary connection (TCPC) is a low-energy system which operation and efficiency are subjected to multiple factors. Some retrospective studies report that the abnormal narrowing of vessels in the system, i.e. stenosis, is one of the most dangerous geometric factors which can result in heart failure.In the present study, the effect of varying extracardiac conduit (ECC) stenosis on the hemodynamics in a surrogate TCPC model is investigated using high-fidelity numerical simulations. The efficiency of the surrogate TCPC model was quantified according to the power loss, relative perfusion in lungs and the percentage of conduit surface area with abnormally low and high wall shear stress for venous flow. Additionally, the impact of respiration and asymmetry in the stenosis geometry to the system was examined. The results show that the flow in the TCPC model exhibits pronounced unsteadiness even under the steady initial boundary conditions, while the uneven pulmonary flow distribution and the presence of the ECC stenosis amplify the chaotic nature of the flow. Energy efficiency of the system is shown to strongly correlate with amount of vortical structures in the model and their range of scales. Finally, the study demonstrates that the presence of respiration in the model adds to perturbations in the flow which causes increase in the power loss. Results obtained in the study provide valuable insights on how the ECC stenosis effect the flow in the surrogate TCPC model under different flow conditions.

Impact of Stenosis Geometry on Blood Flow Behavior in Human Artery

Atherosclerosis in human arteries affects the blood flow behaviour in different ways and sometimes leads to fatal diseases. This study is focused on the impact of the elasticity of human arteries and the geometry of stenosis on non-Newtonian blood flow across the constricted arteries. The mathematical analysis is carried out using MatLab software. The elastic nature of human arteries and the non-Newtonian nature of blood are described under the power-law, Herschel-Bulkley and Casson model. The numerical derivations for blood flow velocity, volume flow rate and wall shear stress are derived for all three types of the model under consideration and results are also depicted graphically. The influence of elasticity, flow index, yield stress and geometry of stenosis on the blood flow is examined. Power-law model gives higher velocity as compared to Herschel-Bulkley model for the fixed magnitude of flow index 𝑛. It is observed that in the constricted region, the volume flow rate amplifies with the increasing value of stenosis shape parameter 𝑚 for the fixed magnitude of flow index 𝑛. The height of stenosis has a diminishing effect on the flow rate. A comparative analysis of the outcomes of the present study and that of the other published work is carried out for authentication.

The Comparative Method Based on Coronary Computed Tomography Angiography for Assessing the Hemodynamic Significance of Coronary Artery Stenosis

PurposeAn important aspect in the prevention and treatment of coronary artery disease is the functional evaluation of narrowed blood vessels. Medical image-based Computational Fluid Dynamic methods are currently increasingly being used in the clinical setting for flow studies of cardio vascular system. The aim of our study was to confirm the feasibility and functionality of a non-invasive computational method providing information about hemodynamic significance of coronary stenosis.MethodsA comparative method was used to simulate the flow energy losses in real (stenotic) and reconstructed models without (reference) stenosis of the coronary arteries under stress test conditions, i.e. for maximum blood flow and minimal, constant vascular resistance.In addition to the absolute pressure drop in the stenotic arteries (FFRsten) and in the reconstructed arteries (FFRrec), a new energy flow reference index (EFR) was also defined, which expresses the total pressure changes caused by stenosis in relation to the pressure changes in normal coronary arteries, which also allows a separate assessment of the haemodynamic significance of the atherosclerotic lesion itself. The article presents the results obtained from flow simulations in coronary arteries, reconstructed on the basis of 3D segmentation of cardiac CT images of 25 patients from retrospective data collection, with different degrees of stenoses and different areas of their occurrence.ResultsThe greater the degree of narrowing of the vessel, the greater drop of flow energy. Each parameter introduces an additional diagnostic value. In contrast to FFRsten, the EFR indices that are calculated on the basis of a comparison of stenosed and reconstructed models, are associated directly with localization, shape and geometry of stenosis only. Both FFRsten and EFR showed very significant positive correlation (P < 0.0001) with coronary CT angiography–derived FFR, with a correlation coefficient of 0.8805 and 0.9011 respectively.ConclusionThe study presented promising results of non-invasive, comparative test to support of prevention of coronary disease and functional evaluation of stenosed vessels.

Analysis identifying minimal governing parameters for clinically accurate in silico fractional flow reserve.

Personalized hemodynamic models can accurately compute fractional flow reserve (FFR) from coronary angiograms and clinical measurements (FFR ), but obtaining patient-specific data could be challenging and sometimes not feasible. Understanding which measurements need to be patient-tuned vs. patient-generalized would inform models with minimal inputs that could expedite data collection and simulation pipelines. To determine the minimum set of patient-specific inputs to compute FFR using invasive measurement of FFR (FFR ) as gold standard. Personalized coronary geometries ( ) were derived from patient coronary angiograms. A computational fluid dynamics framework, FFR , was parameterized with patient-specific inputs: coronary geometry, stenosis geometry, mean arterial pressure, cardiac output, heart rate, hematocrit, and distal pressure location. FFR was validated against FFR and used as the baseline to elucidate the impact of uncertainty on personalized inputs through global uncertainty analysis. FFR was created by only incorporating the most sensitive inputs and FFR additionally included patient-specific distal location. FFR was validated against FFR via correlation ( , ), agreement (mean difference: ), and diagnostic performance (sensitivity: 89.5%, specificity: 93.6%, PPV: 89.5%, NPV: 93.6%, AUC: 0.95). FFR provided identical diagnostic performance with FFR . Compared to FFR vs. FFR , FFR vs. FFR had decreased correlation ( , ), improved agreement (mean difference: ), and comparable diagnostic performance (sensitivity: 79.0%, specificity: 90.3%, PPV: 83.3%, NPV: 87.5%, AUC: 0.90). Streamlined models could match the diagnostic performance of the baseline with a full gamut of patient-specific measurements. Capturing coronary hemodynamics depended most on accurate geometry reconstruction and cardiac output measurement.

Non-Newtonian blood flow model with the effect of different geometry of stenosis

The objective of this paper is to present a non-Newtonian blood flow model with the effect of different geometry of stenosis on various flow quantities. The Power-law model is considered to explore the non-Newtonian property of blood. Two-point Gauss quadrature formula is applied to obtain the numerical expressions of dimensionless flow resistance, skin-friction and flow rate. The variation of dimensionless flow resistance, skin-friction and flow rate with degree of stenosis, axial distance and power-law index is shown graphically. Moreover, the power-law index is adjusted to explore the non-Newtonian characteristics of blood. The importance of the present work has been carried out by comparing the results with other theories both numerically and graphically. It has been found that resistance to flow becomes maximum with total blockage of artery for different shape of stenosis.

Investigating the effect of injection rate on the capture efficiency of nanoparticles in different geometries of stenosed vessel

In this study, the effect of injection speed on the capture efficiency (CE) of nanoparticles under the influence of a magnetic field produced by a current-carrying wire is investigated. Three scenarios have been considered for the geometry of stenosis: (1) symmetrical stenosis, (2) upper wall stenosis, and (3) lower wall stenosis. The non-Newtonian behavior of blood has been modeled using the Carreau model. The effect of different parameters, including magnetic field, drag force, particle diameter, injection speed, blood velocity, and the shape of stenosis on the CE of nanoparticles, is investigated. Considering the injection speed along with non-Newtonian model in a vessel with stenosis is not addressed yet, and are investigated in the present study. The results show that blood velocity and particle diameter have a significant effect on the CE of nanoparticles. Besides, it was revealed that there is a threshold for current intensity (I = 0.009A). At the threshold, CE of nanoparticles is maximum (27.5%), and further increase in current intensity resulting in a dramatic reduction in CE. In all scenarios, as the injection speed increases, the CE of nanoparticles decreased. For example, for scenario 3, as the injection speed increased from 75 mm/s to 200 mm/s, the CE of nanoparticles reduced from 25% to 7.5%, respectively. Besides, for same injection speed, for example 75 mm/s, the CE of scenarios 1, 2, and 3 are 3%, 22.5%, and 25%, respectively. The upper wall stenosis is desired scenario in which the maximum carrier particles are captured at tumor site.

Stenosis simulation of femoral arteries using an adaptive 3D-printed actuator

Motivated by the need for a simulator for varying degrees of vascular stenosis and different stenosis geometries, a pneumatic actuator was conceived and developed using additive manufacturing. This actuator includes flexible and rigid parts. The flexible components yield to incoming air pressure, so varying degrees of stenosis can be simulated based on the air pressure used. The primary benefits of such an actuator are the lack of artifact-causing metal parts and the design flexibility additive manufacturing allows. Thus, such an actuator is useful in cardiovascular studies using MRI, CT, or MPI, as various stenosis geometries and degrees of vascular stenosis can be simulated.

Effect of real and whole blood rheology on flow through an axisymmetric stenosed artery

This study presents an extensive numerical investigation on the flow phenomena of a blood analogous fluid through an axisymmetric stenosed artery under both steady and pulsatile flow conditions. Most of the previous investigations, carried out for this benchmark problem, used either a simple Newtonian fluid model or a generalized Newtonian (GNF) fluid model like the power-law or Bingham plastic fluid model to represent the rheological behaviour of blood. However, many prior rheological studies showed that the real and whole blood exhibits both the shear-thinning and viscoelastic properties. In this study, for the first time, a multi-mode sPTT (simplified Phan-Thein-Tanner) model is used to carry out the numerical computation, which accounts for both the shear-thinning and viscoelastic rheological properties of blood. Additionally, a realistic set of viscoelastic model parameters, obtained by fitting the response of real and whole blood in standard viscometric flows, is used in this study. An excellent agreement is seen between the experimentally determined apparent viscosity (in simple shear flows) of blood with that predicted by the present viscoelastic model and other prior models developed for blood. Therefore, we believe that this study presents more accurate and realistic numerical results for the flow of blood through a stenosed artery than that presented by the previous studies in the literature. A simple Newtonian fluid model is also used in the present analysis to compare and show how the flow behavior of blood can be influenced by its complex rheological properties under otherwise identical conditions. We find a significant difference in the flow characteristics (in terms of the streamline profiles, velocity magnitude, pressure drop, etc.) obtained with the Newtonian and viscoelastic fluid models. For instance, the velocity gradient is seen to be large near the artery wall for the viscoelastic fluid model than that seen for the Newtonian model; whereas, a reverse trend is seen for the pressure drop across the stenosis. Furthermore, we find that the flow dynamics is strongly modulated by the stenosis geometry, Reynolds number and flow types, i.e., whether it is steady or pulsatile.

Influence of Turbulence in Aorta-like Tube: Computational and Experimental Study

The presented paper aims at comparison of modelling approaches to a pulsatile fluid flow in aorta-like tube; it investigates their influence on the shape of the velocity profiles and waveforms, and consequently on wall shear stress. Comparisons of computational results between rigid and compliant tubes with laminar and low Re turbulent models of fluid are presented. The results were validated with PIV experimental data through the velocity profile in the half-length section of the tube for both cases (rigid and compliant) and the overall agreement was very good, almost perfect for the rigid case. Frequency of the pulse pump in the experimental circuit was 1Hz, the diameter of the tube ~ 20 mm, and maximum deformation of the compliant tube during a period was 12%. The turbulent model improved the agreement with the experimental data by flattening the velocity profiles in both cases, but the effect was much more pronounced for the compliant tube, especially during the deceleration phase. This work confirms the hypothesis stated by Brindise and Vlachos (2018) that a longer deceleration phase triggers transition to turbulence. We put foundations for extension of this hypothesis to compliant tubes where this conclusion was confirmed for physiological Reynolds and Womersley numbers. The main outputs of this study are: (i) the length of deceleration phase should be considered (in addition to the geometry or severity of stenosis) in decision whether fluid simulations should be performed with or without laminar flow assumption; (ii) for fluid simulations of blood vessels considering their compliance, a special care should be devoted to time synchronization between BCs to prevent unphysiological waveforms.

Lesion Geometry as Assessed by Optical Coherence Tomography Is Related to Myocardial Ischemia as Determined by Cardiac Magnetic Resonance Imaging.

Introduction: Although the relationship between the geometry of coronary stenosis and the presence of myocardial ischemia is well known, the association between stenosis geometry and severity and/or extent of ischemia is still unexplored. Thus, we investigated this relationship using optical coherence tomography (OCT) to assess stenosis parameters and cardiac magnetic resonance imaging (CMR) to determine both extent and severity of ischemia. Methods: We analyzed 55 lesions from 51 patients with stable angina. Pre-interventionally, all patients underwent OCT-analysis of stenosis morphology as well as CMR to determine both the extent and severity of myocardial ischemia. Results: Percent area stenosis (%AS) was significantly associated with ischemic burden (r = 0.416, p = 0.003). Similar results could be obtained for other stenosis parameters as well as for several other parameters assessing the extent of ischemia. Furthermore, OCT-derived stenosis parameters were associated with the product of ischemic burden and severity of ischemia (%AS: r = 0.435, p = 0.002; similar results for other parameters). A Poiseuille’s-law-modelled combination of stenosis length and minimal lumen diameter yielded a good diagnostic efficiency (AUC 0.787) in predicting an ischemic burden >10%. Conclusions: Our data highlight the key role of the geometry of coronary lesions in determining myocardial ischemia.

Mathematical modeling of non-Newtonian fluid in arterial blood flow through various stenoses

Since the stenosis geometry of some cardiovascular patients cannot be described by a vertically symmetric function throughout the stenosis, so it motivates us to study the blood flow through a vertically asymmetric stenosis. In addition, we compare the flow quantities in bothvertically symmetric and asymmetric stenoses. The vertically symmetric stenosis is explained by a vertically symmetric function such as an exponential function in bell shape and a cosine function in cosine shape. The vertically asymmetric stenosis is interpreted by a vertically asymmetric function such as the combination of two different stenosis shapes. Blood is treated as a non-Newtonian fluid which is represented in the power-law model. The finite difference scheme is used to solve governing equations for obtaining the flow quantities such as axial velocity, radial velocity, flow rate, resistance to flow, and skin friction. We investigated the way that the stenosis height, stenosis length, and non-Newtonian behavior affect the flow quantities through three various stenoses. The flow quantities in the bell shape and cosine shape of stenosis show significantly different behavior. Moreover, we found that the flow quantities in the single shape (bell shape or cosine shape) have the same behavior as the flow quantities in the combined shape in the first half part, but have a slightly different behavior in the last half part.

Investigation of the plaque morphology effect on changes of pulsatile blood flow in a stenosed curved artery induced by an external magnetic field

In a new therapeutic technique, called magnetic drug targeting (MDT), magnetic particles carrying therapeutic agents are directed to the target tissue by applying an external magnetic field. Meanwhile, this magnetic field also affects the blood as a biomagnetic fluid. Therefore, it is necessary to select a magnetic field with an acceptable range of influence on the blood flow. This study investigates the effect of an external magnetic field on the pulsatile blood flow in a stenosed curved artery to identify a safe magnetic field. The effects of a number of parameters, including the magnetic susceptibility of blood in oxygenated and deoxygenated states and the magnetic field strength, were studied. Moreover, the effect of the plaque morphology, including the occlusion percentage and the chord length of the stenosis, on changes in blood flow induced by the magnetic field was investigated. The results show that applying a magnetic field increases the wall shear stress (WSS) and the pressure of the deoxygenated blood. Comparing the wall shear stresses of the deoxygenated and oxygenated blood shows that the effect of magnetic field on the deoxygenated blood is more significant than its effect on the oxygenated blood due to its higher magnetic susceptibility. The study of the stenosis geometry shows that the influence of magnetic field on the blood flow is increased by decreasing the occlusion percentage of the artery. Furthermore, among the evaluated lengths, the 50° chord length results in the highest variation under the influence of the magnetic field. Finally, the magnetic field of Mn = 2.5 can be utilized as a safe field for MDT purposes in such a stenosed curved artery.

Myocardial contractility recovery following acute pressure unloading after transcatheter aortic valve intervention (TAVI)\xa0in patients with severe aortic stenosis and different left ventricular geometry:\xa0a multilayer longitudinal strain echocardiographicanalysis

Aim of the present study was to describe the left ventricular longitudinal strain (LS) in all myocardial layers in patients with severe aortic stenosis (AS), preserved left ventricular ejection fraction (LVEF) in different LV geometry and to compare LS analysis before and early after acute LV unloading provided by transcatheter aortic valve implantation (TAVI). 68 patients were enrolled. LS was measured from the endocardial layer (Endo-LS), epicardial layer (Epi-LS) and full thickness of myocardium (Transmural-LS) before and after TAVI. Patients were divided in two groups accordingly with relative wall thickness (RWT): concentric LV hypertrophy (cLVH) vs eccentric LV hypertrophy (eLVH). Less impaired values of LS at baseline were observed, in all layers, in patients with cLVHas compared to patients with eLVH (Endo-LS was − 13.2 ± 2 vs − 11.1±3 %, p = 0.041; Epi-LS was − 11.8 ± 1.8 vs − 9.9 ± 3 %, p = 0.043; Transmural-LS was − 12.3 ± 1.8 vs − 10.49 ± 3.3 %, p = 0.02, respectively). A significant improvement in endocardial LS (Endo-LS) after TAVI was detected only in cLVH(− 13 ± 2 vs − 14 ± 2, p = 0.011). Our findings documented that concentric LVH had better basal strain function and showed a better myocardial recovery after TAVI compared to eLVH.

Subglottic Stenosis Position Affects Work of Breathing.

Subglottic stenosis (SGS) is the most common type of laryngeal stenosis in neonates. SGS severity is currently graded based on percent area of obstruction (%AO) via the Myer-Cotton grading scale. However, patients with similar %AO can have widely different clinical courses. Computational fluid dynamics (CFD) based on patient-specific imaging can quantify the relationship between airway geometry and flow dynamics. We investigated the effect of %AO and axial position of SGS on work of breathing (WOB) in neonates using magnetic resonance imaging. High-resolution ultrashort echo-time MRI of the chest and airway was obtained in three neonatal patients with no suspected airway abnormalities; images were segmented to construct three-dimensional (3D) models of the neonatal airways. These models were then modified with virtual SGSs of varying %AO and axial positioning. CFD simulations of peak inspiratory flow were used to calculate patient-specific WOB in nonstenotic and artificially stenosed airway models. CFD simulations demonstrated a relationship between stenosis geometry and WOB increase. WOB rapidly increased with %AO greater than about 70%. Changes in axial position could also increase WOB by approximately the same amount as a 10% increase in %AO. Increased WOB was particularly pronounced when the SGS lumen was misaligned with the glottic jet. The results indicate a strong, predictable relationship between WOB and axial position of the stenotic lumen relative to the glottis, which has not been previously reported. These findings may lead to precision diagnosis and treatment prediction tools in individual patients. 4 Laryngoscope, 131:E1220-E1226, 2021.

Analysis of Different Stenotic Geometries on Two-Phase Blood Flow

There are many different mathematical models and solution techniques dealing with the blood flows. A two-phase (liquid-solid) model solved by a perturbation method will be introduced. Effects of hematocrit, Reynolds number, area reduction, and different geometries of the stenotic channel are studied on the velocity, pressure gradient, and streamlines. The flow characteristics (velocity and pressure) give a great increase as the stenosis classified as a sever stenosis. It is found that, the stenosis geometry has a great effect on the pressure gradient in the axial direction, and also there is a change in velocity profile in each cross section of the geometry. The hematocrit has a noticed effect on the flow velocity and pressure gradient, in which as the hematocrit increases the maximum velocity decreases before the throat while it increased after that section.

Numerical investigation of renal artery hemodynamics based on the physiological response to renal artery stenosis

Renal Artery Stenosis (RAS) is the narrowing of renal arteries, most often caused by atherosclerosis or fibromuscular dysplasia. Possible complications of renal artery stenosis are renovascular hypertension and renal ischemia. The goals of the current study were to investigate the physiological response to RAS and effects of the artery and stenosis geometry, quantify the performance of arterial pressure regulation mechanisms respect to stenosis severity, and predict future conditions of renal artery stenosis. Commercial software based on the finite volume method was utilized to solve governing equations. To determine the physiological response, simulations were done for two cases, with and without the involvement of arterial pressure regulation mechanisms. The numerical method was validated by experimental data, which obtained from two prototypes. Results showed that systemic blood pressure was increased as the physiological response to RAS; hence, the flow rate of the renal branch was improved and renal ischemia was relatively prevented. Furthermore, results demonstrated that the stenosis percentage and artery diameter were dominant geometric parameters on the hemodynamics and other parameters had negligible effects. It was demonstrated that 50% of stenosis was the critical point for the interaction of RAS and arterial pressure regulation mechanisms. Finally, wall shear stress was analyzed on an image-based geometry, and it was estimated and expected that acute renal artery stenosis was progressive and pathogenesis of arterial diseases.

The Interplay between Features of Plaque Vulnerability and Hemodynamic Relevance of Coronary Artery Stenoses

Fractional flow reserve (FFR) may not be immune from hemodynamic perturbations caused by both vessel and lesion related factors. The aim of this study was to investigate the impact of plaque- and vessel wall-related features of vulnerability on the hemodynamic effect of intermediate coronary stenoses. Methods and Results: In this cross-sectional study, patients referred to catheterization laboratory for clinically indicated coronary angiography were prospectively screened for angiographically intermediate stenosis (50–80%). Seventy lesions from 60 patients were evaluated. Mean angiographic stenosis was 62.1 ± 16.3%. After having performed FFR assessment, intravascular ultrasound (IVUS) was performed over the FFR wire. Virtual histology IVUS was used to identify the plaque components and thin cap fibroatheroma (TCFA). TCFA was significantly more frequent (65 vs. 38%, p = 0.026), and necrotic core volume (26.15 ± 14.22 vs. 16.21 ± 8.93 mm³, p = 0.04) was significantly larger in the positively remodeled than non-remodeled vessels. Remodeling index correlated with necrotic core volume (r = 0.396, p = 0.001) and with FFR (r = –0. 419, p = 0.001). With respect to plaque components, only necrotic core area (r = –0.262, p = 0.038) and necrotic core volume (r = –0.272, p = 0.024) were independently associated with FFR. In the multivariable model, presence of TCFA was independently associated with significantly lower mean FFR value as compared to absence of TCFA (adjusted, 0.71 vs. 0.78, p = 0.034). Conclusion: The current study demonstrated that for a given stenosis geometry, features of plaque vulnerability such as necrotic core volume, TCFA, and positive remodeling may influence the hemodynamic relevance of intermediate coronary stenoses.