Coronary artery wall shear stress is associated with progression and transformation of atherosclerotic plaque and arterial remodeling in patients with coronary artery disease

Defining "Vulnerable" in coronary artery disease: predisposing factors and preventive measures

The likelihood of a plaque to cause an acute coronary syndrome (ACS) depends on several factors, both lesion- and patient-related. One of the most investigated and established contributing factors is the presence of high-risk or "vulnerable plaque" characteristics, which have been correlated with increased incidence of major adverse cardiovascular events (MACE). The recognition, however, that a significant percentage of vulnerable plaques do not result in causing clinical events has led the scientific community towards the more multifaceted concept of "vulnerable patients". Incorporating the morphological features of an atherosclerotic plaque into its hemodynamic surroundings can better predict the chance of its disruption, as altered fluid dynamics play a significant role in plaque destabilization. The advances in coronary imaging and the field of computational fluid dynamics (CFD) can contribute to develop more accurate lesion- and patient-related ACS prediction models that take into account both the morphology of a plaque and the forces applied upon it. The aim of this review is to provide the latest data regarding the aforementioned predictive factors as well as relevant preventive measures.

Impact of the stent footprint on endothelial wall shear stress in patient-specific coronary arteries: A computational analysis from the SHEAR-STENT trial

BACKGROUND AND OBJECTIVE

Wall shear stress (WSS) has been known to play a critical role in the development of several complications following coronary artery stenting, including in-stent restenosis and thrombosis. Computational fluid dynamics is often used to quantify the post-stenting WSS, which may potentially be used as a predictive metric. However, large-scale studies for WSS-based risk stratification often neglect the footprint of the stent due to reconstruction challenges. The primary objective of this study is to statistically evaluate the impact of the stent footprints (Xience and Resolute stents) on the computed endothelial WSS and quantitatively identify the relationship between these local hemodynamic alterations and the global properties of the vessel, such as curvature, on WSS. The ultimate goal is to evaluate whether and when it is worth including the footprint of the stent in an in-silico study to compute the WSS reliably.

METHODS

A previously developed semi-automated reconstruction approach for patient-specific coronaries was employed as a part of the SHEAR-STENT trial. A subset of patients was analyzed (N=30), and CFD simulations were performed with and without the stent to evaluate the impact of the stent footprint on WSS. Due to the computationally expensive nature of transient analyses, a sub-cohort of ten patients were used to assess the reliability of WSS obtained from steady computations as a surrogate for the time-averaged results. Global and local vessel curvature data were extracted for all cases and evaluated against stent-induced alterations in the WSS. The differences between the Xience and Resolute stent platforms were also examined to quantify each stent's unique WSS footprint.

RESULTS

Results from the surrogate analysis indicate that steady WSS serves as an excellent approximation of the time-averaged computations. The presence of either stent footprint causes a statistically significant decrease in the space-averaged WSS, and a significant increase in the endothelial regions exposed to very low WSS as well (<0.5 Pa). Negative correlations were observed between vessel curvature and WSS differences, indicating that macroscopic vessel characteristics play a more prominent role in determining endothelial WSS at higher curvature values. In our pool of cases, comparison of Xience and Resolute stents revealed that the Resolute platform seems to lead to lower space-averaged WSS and an increase in areas of very low WSS.

CONCLUSION

These results outline (1) the necessity of including the stent footprint for accurate in-silico WSS analysis; (2) the global features of stented arteries serving as the dominant determinant of WSS past a certain curvature threshold; and (3) the Xience stent resulting in a milder presence of hemodynamically unfavorable WSS regions compared to the Resolute stent.

Systematic Review of Biomechanical Forces Associated with Carotid Plaque Disruption and Stroke

OBJECTIVE

Carotid plaque disruption with release of atheroembolic debris and consequent brain infarction is the primary mechanism for brain injury in patients with carotid stenosis. Disease severity is traditionally quantified by the degree of stenosis, though it is not an accurate marker of stroke-risk. It has been proposed that biomechanical forces acting on a carotid plaque may render it vulnerable to rupture by causing adverse remodeling of its morphology, or by direct disruption. We conducted a systematic review to assess the forces acting on carotid plaques and their relationship to adverse plaque outcomes.

METHODS

A literature search for studies reporting measurements of flow-related biomechanical forces acting on carotid atherosclerotic plaques was conducted using PubMed, Embase and Web of Science. Studies were included if they reported on human carotid plaques, used patient-specific geometry, measured forces on or in the atherosclerotic lesions, and reported on carotid plaque-related adverse outcomes.

RESULTS

Of 5,635 manuscripts screened, 154 met eligibility criteria. Forces were computed using patient-specific arterial geometry derived from multiple imaging modalities, mainly magnetic resonance imaging (58.4%) and ultrasonography (25.3%). Methodologies used to quantify the forces included computational fluid dynamics (31.8%), finite element analysis (10.4%), fluid-structure interaction models (27.3%), in-vivo measurements (29.9%), or in-vitro assessments (0.6%). Wall shear stress (WSS) and plaque wall stress (PWS) were the most frequently measured forces, in 72.1% and 45.5% of studies respectively. Principal PWS (n=15 studies) and WSS (n=21 studies) were elevated in patients with adverse outcomes. PWS levels of >160 kPa had a sensitivity of >80% and specificity of >75% in identifying patients with adverse events. Increasing PWS was associated with subsequent ischemic cerebrovascular events (HR=12.98 per 1 kPa increase, p=0.02). WSS levels of >50 dyn/cm2 had a sensitivity of 100% and specificity of 67% in differentiating patients with adverse events (plaque rupture, cerebral infarction, stroke, or transient ischemic attack) compared to those without.

CONCLUSIONS

There is heterogeneity in sample size, study design, imaging protocols, image-processing methodology, forces assessed, and adverse carotid plaque-related outcomes measured in the literature. Despite these limitations, increasing PWS and WSS were consistently associated with adverse plaque outcomes, and predicted adverse outcomes with moderate to high degrees of sensitivity and specificity. Since the information available is heterogenous, these relationships need to be confirmed in larger prospective studies.

Predicting Milk Flow Behavior in Human Lactating Breast: An Integrated Machine Learning and Computational Fluid Dynamics Approach

This study develops a comprehensive framework that integrates computational fluid dynamics (CFD) and machine learning (ML) to predict milk flow behavior in lactating breasts. Utilizing CFD and other high-fidelity simulation techniques to tackle fluid flow challenges often entails significant computational resources and time investment. Artificial neural networks (ANNs) offer a promising avenue for grasping complex relationships among high-dimensional variables. This study leverages this potential to introduce an innovative data-driven approach to CFD. The initial step involved using CFD simulations to generate the necessary training and validation datasets. A machine learning pipeline was then crafted to train the ANN. Furthermore, various ANN architectures were explored, and their predictive performance was compared. The design of experiments method was also harnessed to identify the minimum number of simulations needed for precise predictions. This study underscores the synergy between CFD and ML methodologies, designated as ML-CFD. This novel integration enables a neural network to generate CFD-like results, resulting in significant savings in time and computational resources typically required for traditional CFD simulations. The models developed through this ML-CFD approach demonstrate remarkable efficiency and robustness, enabling faster exploration of milk flow behavior in individual lactating breasts compared to conventional CFD solvers.

FBXO38 Regulates Nox1 Stability to Reduce Vascular Endothelial Damage Induced by Low Oscillatory Shear Stress

Oxidative stress and endothelial dysfunction are critical drivers of atherosclerosis, but the mechanisms regulating oxidative stress under disturbed flow conditions remain incompletely understood. The ubiquitin-proteasome system, particularly E3 ubiquitin ligases, may play a pivotal role in modulating these processes. FBXO38, an E3 ligase involved in proteasomal degradation, has been implicated in various physiological pathways, but its role in regulating oxidative stress in endothelial cells is unknown. We hypothesized that FBXO38 mitigates endothelial damage induced by low oscillatory shear stress (LOSS) by promoting the ubiquitin-proteasome-dependent degradation of Nox1, a major source of reactive oxygen species (ROS). Using an in vitro LOSS model in human umbilical vein endothelial cells (HUVECs) and an in vivo mouse partial carotid ligation model, we assessed the expression of FBXO38 and Nox1 through quantitative PCR, western blotting, immunofluorescence, and immunohistochemistry. LOSS significantly reduced FBXO38 protein expression (by ~60%, p < 0.0001 at 24 h), leading to increased Nox1 protein levels (approximately two-fold, p < 0.001) and apoptosis. FBXO38 overexpression markedly attenuated Nox1 accumulation (~50% reduction, p < 0.05), reduced ROS production, and improved cell viability under LOSS conditions, whereas FBXO38 knockdown exacerbated these effects. Moreover, FBXO38 directly interacted with Nox1, suggesting a ubiquitin-dependent degradation mechanism. Our results reveal that FBXO38 regulates endothelial oxidative stress by controlling Nox1 stability under disturbed shear stress conditions. Although FBXO38 emerges as a promising candidate for therapeutic targeting, further studies are necessary to validate its potential in preclinical and clinical settings.

Could Right Coronary Artery-Aorta Angle be Used to Predict Atherosclerotic Lesion Localization in Critical Site of the Right Coronary Artery in Patients With Right Dominancy?

BACKGROUND

This study aimed to evaluate the impact of the aorta-right coronary artery angle (ARA) on lesion localization and its protective effect in the critical osteal region in patients with dominant right coronary artery (RCA).

METHODS

This cross-sectional study included 294 patients who underwent elective coronary angiography for stable angina pectoris and had a single significant lumen stenosis (50%-95%) before the RCA crux. Patients with tortuous vessels, previous interventions, left-dominant circulation, or insufficient image quality were excluded. ARA, lesion criticality, length, and distance from the aorto-osteal junction were calculated using quantitative coronary analysis. Patients were categorized based on lesion location: osteal, proximal, mid, and distal regions.

RESULTS

ARA increased significantly as the lesion localization moved distally (osteal: 53.26° ± 5.65°, proximal: 60.79° ± 9.53°, mid: 82.33° ± 9.85°, distal: 93.53° ± 7.46°; p < 0.0001). A strong positive correlation was found between ARA and the distance of the lesion from the aorto-osteal junction (r = 0.759, p < 0.0001). In binary regression, ARA was the only independent risk factor for critical lesion localization in the osteal region (OR = 0.915; 95% CI 0.868-0.965, p < 0.001). ROC analysis showed that an ARA > 73.50° had 83.2% sensitivity and 81.3% specificity for excluding critical lesions in the osteal region (AUC = 0.861; 95% CI 0.815-0.907).

CONCLUSION

A narrow ARA increases the likelihood of critical lesions in the osteal RCA, while an ARA > 73.50° is protective. These findings suggest ARA could guide risk assessment and treatment planning in coronary interventions.

Enhanced External Counterpulsation Intervention Induces the Variation of Physiological Parameters and Shear Stress Metrics in the Carotid Artery

Enhanced external counterpulsation (EECP) treatment has been demonstrated to be effectively vasculoprotective and anti-atherosclerotic in clinical observations and controlled trials. The diastolic blood flow augmentation induced by EECP greatly affected the local hemodynamic environment in multiple arterial segments. In this study, a porcine model of hypercholesterolaemia was developed to perform an invasive physiological measurement involving electrocardiogram, blood flow wave, and arterial pressure. Subsequently, a three-dimensional carotid bifurcation model was developed to evaluate the variations in wall shear stress (WSS) and its temporal and spatial oscillations. The results show that, compared to the pre-EECP state, EECP stimulus led to an increase of 28.7% in the common carotid artery (CCA) blood flow volume over a cardiac cycle, as well as an augmentation of 22.73% in the diastolic pressure. Meanwhile, the time-average wall shear stress (TAWSS) over the cardiac cycle increased 25.1%, while the relative residence time (RRT) declined 45.7%. These results may serve to reveal the hemodynamic mechanism of EECP treatment that contributes to its anti-atherosclerotic effects.

Bridging hemodynamics, tissue mechanics, and pathophysiology in coronary artery disease: A new agent-based model with tetrahedral mesh integration

We introduce a new multi-physics, multi-scale modeling approach to understand plaque progression during coronary artery disease. Prior works have coupled agent-based models (ABMs) with finite element analysis (FEA) or computational fluid dynamics (CFD) to study the individual contributions of tissue mechanics or hemodynamics to plaque growth. However, these approaches could not simultaneously capture the dynamic interplay between all three domains that drive plaque development. This study aims to present a novel method that merges hemodynamics via CFD, biological processes via ABM, and biomechanics via FEA into a single multi-scale, multi-physics simulation (CAFe). A description of the mechanisms and modeling approaches utilized in the CAFe model is provided, as well as preliminary exploration of the model's capabilities in idealized healthy and stenosed coronary artery models. A volumetric 3D tetrahedral mesh of the artery is shared between CFD, ABM, and FEA to simulate geometrical and biological changes with continuity and consistency. The CFD and FEA modules, implemented with FEBio, calculate the wall shear stress and structural stress and strain, respectively. These biomechanical values are passed to the ABM, implemented in MATLAB, which simulates vascular remodeling using molecular diffusion, cell migration, equations for cellular processes, and volumetric growth to update the geometry. Initial results using CAFe suggest atherosclerotic arteries seek to maintain a hemodynamic threshold through preferential growth and remodeling downstream of a stenosis. The innovative approach described herein marks a significant step forward in predictive modeling of CAD progression and paves the way for powerful coupling of the spatiotemporal-dependent remodeling paradigms exhibited by the disease.

Biophysical and Biochemical Roles of Shear Stress on Endothelium: A Revisit and New Insights

Hemodynamic shear stress, the frictional force exerted by blood flow on the endothelium, mediates vascular homeostasis. This review examines the biophysical nature and biochemical effects of shear stress on endothelial cells, with a particular focus on its impact on cardiovascular pathophysiology. Atherosclerosis develops preferentially at arterial branches and curvatures, where disturbed flow patterns are most prevalent. The review also highlights the range of shear stress across diverse human arteries and its temporal variations, including aging-related alterations. This review presents a summary of the critical mechanosensors and flow-sensitive effectors that respond to shear stress, along with the downstream cellular events that they regulate. The review evaluates experimental models for studying shear stress in vitro and in vivo, as well as their potential limitations. The review discusses strategies targeting shear stress, including pharmacological approaches, physiological means, surgical interventions, and gene therapies. Furthermore, the review addresses emerging perspectives in hemodynamic research, including single-cell sequencing, spatial omics, metabolomics, and multiomics technologies. By integrating the biophysical and biochemical aspects of shear stress, this review offers insights into the complex interplay between hemodynamics and endothelial homeostasis at the preclinical and clinical levels.

Hemodynamics of Proximal Coronary Lesions in Patients Undergoing Transcatheter Aortic Valve Implantation: Patient-Specific In Silico Study

Aortic stenosis (AS) frequently coexists with coronary artery disease (CAD), complicating revascularization decisions. The use of coronary physiology indices, such as the fractional flow reserve (FFR), instantaneous wave-free ratio (iFR), and coronary flow reserve (CFR), in AS patients remains debated, particularly after transcatheter aortic valve implantation (TAVI). In this study, we employ computational fluid dynamics (CFD) to evaluate coronary hemodynamics and assess changes in the wall shear stress (WSS) before and after TAVI. Our analysis demonstrates strong agreement between CFD-derived and invasive FFR measurements, confirming CFD's reliability as a non-invasive tool for coronary physiology assessment. Furthermore, our results show no significant changes in FFR (p=0.92), iFR (p=0.67), or CFR (p=0.34) post-TAVI, suggesting that these indices remain stable following aortic valve intervention. However, a significant reduction in high WSS exposure (59% to 40.8%, p<0.001) and the oscillatory shear index (OSI: 0.32 to 0.21, p<0.001) was observed, indicating improved hemodynamic stability. These findings suggest that coronary physiology indices remain reliable for revascularization guidance post-TAVI and highlight a potential beneficial effect of aortic stenosis treatment on plaque shear stress dynamics. Our study underscores the clinical utility of CFD modeling in CAD management, paving the way for further research into its prognostic implications.

Hemodynamics of distal cerebral arteries are associated with functional outcomes in symptomatic ischemic stroke in middle cerebral artery territory: A four-dimensional flow cardiovascular magnetic resonance study

BACKGROUND

Cerebrovascular hemodynamics are believed to play an important role in the development of ischemic stroke (IS). However, the relationships between hemodynamics and prognosis are not fully understood. Four-dimensional (4D) flow cardiovascular magnetic resonance (CMR) enables comprehensive characteristics of cerebrovascular hemodynamics. This study aims to investigate the associations of the different hemodynamics derived from 4D flow CMR with IS functional outcomes.

METHODS

Ninety-one patients (median age 64 years, 62 males) with unilateral IS in middle cerebral artery (MCA) territory were included. All subjects underwent a CMR scan, including 4D flow, three-dimensional (3D) time-of-flight magnetic resonance angiography, and 3D whole brain black-blood high-resolution vessel wall imaging of the MCA. Six hemodynamic parameters, including flow rate, velocity, pulsatility index, time-averaged wall shear stress (TAWSS), oscillatory shear index, and relative residence time (RRT), were calculated for the lesion site, pre-bifurcation M1 (pM1) segment, and the distal M1 and/or first branches of M2 (dM1/M2) segments. Vessel characteristics, such as lumen area, vessel area, wall area, maximum wall thickness, and the degree of stenosis, were calculated at the most stenotic lesion site. The modified Rankin Scale (mRS) scores were assessed at 90 days and 1 year, and an mRS >2 was considered as a poor functional outcome.

RESULTS

Lower segment-level TAWSS (odds ratio [OR]: 0.24, P = 0.006 and OR: 0.29, P = 0.014), higher RRT (OR: 2.74, P = 0.007 and OR: 2.40, P = 0.011) of dM1/M2 segments, and lower segment- and lesion-level velocity (OR: 0.40, P = 0.019 and OR: 0.41, P = 0.025; OR: 0.41, P = 0.030 and OR: 0.42, P = 0.040) of pM1 segment were observed to be associated with poor functional outcome at both 90 days and 1 year. Using the cut-off value of 3.58 Pa and 0.29, respectively, TAWSS and RRT of dM1/M2 segments showed moderate performance in distinguishing poor functional outcome from favorable outcome (area under the curve ranging from 0.642-0.687) both at 90 days and 1 year.

CONCLUSION

Distal segmental TAWSS and RRT of dM1/M2 segments were associated with poor functional outcomes. Such alterations in hemodynamics might help in the identification of patients with potentially unfavorable prognosis.

The Influence of the Presence of the Ramus Intermedius on Atherosclerosis Plaque Deposition in the Left Bifurcation Region in Low-Risk Individuals

Background

Additional bifurcations at the left main coronary artery (LMCA) could modify the geometry of the left coronary system, disturbing haemodynamic flow patterns and potentially altering endothelial shear stress (ESS). A low ESS has been implicated in atherogenesis. The emergence of the ramus intermedius (RI) from the LMCA creates additional branching, but the specific role of the RI in plaque deposition at the left coronary system remains unclear. This study sought to elucidate the potential effects of the RI on plaque formation at the LMCA and its bifurcation.

Methods

A retrospective cross-sectional single-centre study was conducted using data from 139 female patients who were identified to have low risk of cardiovascular disease. These patients underwent cardiac computed tomography angiography between January 2017 and December 2018. Contrasted multiplanar coronary images taken during the best diastolic phase were analysed for the presence (experimental group) or absence (control group) of the RI. Measurements of plaques were done at the LMCA and at a 10 mm distance from the ostia of daughter arteries. Plaque data at the left bifurcation region were analysed using descriptive statistics, chi-square, and binary logistic regression tests. A p-value of <0.05 was considered statistically significant.

Results

Amongst these low-risk patients, 33.8% (n = 47) had an RI. In the presence of RI, there was an eight-fold increased risk of plaque deposition at the LMCA (adjusted odds ratio, aOR = 8.5) and a three-fold increased risk of plaque deposition at the proximal left anterior descending (pLAD), especially on its lateral wall (aOR = 3.5). However, the RI did not influence plaque deposition at the distance of 10 mm from the ostium of the proximal left circumflex artery.

Conclusions

These findings suggest that the RI increases the risk for atherosclerosis plaque deposition by three to eight-fold at the pLAD artery and the LMCA.

Sensitivity of coronary hemodynamics to vascular structure variations in health and disease

Local hemodynamics play an essential role in the initiation and progression of coronary artery disease. While vascular geometry alters local hemodynamics, the relationship between vascular structure and hemodynamics is poorly understood. Previous computational fluid dynamics (CFD) studies have explored how anatomy influences plaque-promoting hemodynamics. For example, areas exposed to low wall shear stress (ALWSS) can indicate regions of plaque growth. However, small sample sizes, idealized geometries, and simplified boundary conditions have limited their scope. We generated 230 synthetic models of left coronary arteries and simulated coronary hemodynamics with physiologically realistic boundary conditions. We measured the sensitivity of hemodynamic metrics to changes in bifurcation angles, positions, diameter ratios, tortuosity, and plaque topology. Our results suggest that the diameter ratio between left coronary branches plays a substantial role in generating adverse hemodynamic phenotypes and can amplify the effect of other geometric features such as bifurcation position and angle, and vessel tortuosity. Introducing mild plaque in the models did not change correlations between structure and hemodynamics. However, certain vascular structures can induce ALWSS at the trailing edge of the plaque. Our analysis demonstrates that coronary artery vascular structure can provide key insight into the hemodynamic environments conducive to plaque formation and growth.

High Middle Cerebral Artery Wall Shear Stress in Branch Atheromatous Disease: A Computational Fluid Dynamics Analysis

AIM

Branch atheromatous disease (BAD), characterized by the occlusion of perforating branches near the orifice of a parent artery, often develops early neurological deterioration because the mechanisms underlying BAD remain unclear. Abnormal wall shear stress (WSS) is strongly associated with endothelial dysfunction and plaque growth or rupture. Therefore, we hypothesized that computational fluid dynamics (CFD) modeling could detect differences in WSS between BAD and small-vessel occlusion (SVO), both of which result from perforating artery occlusion/stenosis.

METHODS

This cross-sectional observational study included consecutive patients admitted to our institution within 7 days after symptom onset who met the following criteria: absence of stenosis/occlusion in the intracranial major arteries on brain magnetic resonance angiography (MRA) or extracranial carotid arteries on carotid ultrasonography. The WSS and blood flow velocity in the M1 segment of the middle cerebral artery were analyzed using CFD based on MRA.

RESULTS

The number of patients with a WSS ratio (ipsilesional/contralesional) of ＞1 was significantly higher in patients with BAD (n = 27) than in those with SVO (n = 27) [20 (74.1%) vs. 11 (40.7%), p = 0.013]. Higher WSS on ipsilesional M1 than on contralesional M1 was an independent risk factor for BAD (adjusted odds ratio 4.38, 95% confidence interval 1.29-14.82, p = 0.018). Blood flow velocity in the M1 segment was not associated with BAD.

CONCLUSIONS

In patients with BAD, higher M1 segment WSS on CFD can be a risk factor for the development of vulnerable plaques in branch orifices. Moreover, the use of CFD may contribute to the diagnosis of BAD.

Validation of the efficacy of the porous medium model in hemodynamic analysis of iliac vein compression syndrome

Iliac Vein Compression Syndrome (IVCS) is a common risk factor for deep vein thrombosis in the lower extremities. The objective of this study was to investigate whether employing a porous medium model to simulate the compressed region of an iliac vein could improve the reliability and accuracy of Computational Fluid Dynamics (CFD) analysis outcomes of IVCS. Pre-operative Computed Tomography (CT) scan images of patients with IVCS were utilized to reconstruct models illustrating both the compression and collateral circulation of the iliac vein. A porous medium model was employed to simulate the compressed region of the iliac vein. The agreements of times to peak between discrete phase particles in CFD analysis and contrast agent particles in Digital Subtraction Angiography (DSA) were compared. Furthermore, comparisons were made between the CFD analysis results that incorporated the porous media and those that did not. The results revealed that in the CFD analysis incorporating the porous media model, more than 80% of discrete phase particles reached the inferior vena cava via collateral circulation. Additionally, the concentration variation curve of discrete phase particles demonstrated a high concordance rate of 92.4% compared to that obtained in DSA. In comparison to CFD analysis conducted without the porous medium model, the incorporation of the porous medium model resulted in a substantial decrease in blood flow velocity by 87.5% within the compressed region, a significant increase in pressure gradient of 141 Pa between the inferior vena cava and left iliac vein, and a wider distribution of wall shear stress exceeding 2.0 Pa in collateral vessels rather than in the compressed region. The study suggests that the introduction of a porous medium model improves the hemodynamic analysis of patients with IVCS, resulting in a closer alignment with clinical observations. This provides a novel theoretical framework for the assessment and treatment of patients with IVCS.

Relative Residence Time Can Account for Half of the Anatomical Variation in Fatty Streak Prevalence Within the Right Coronary Artery

PURPOSE

The patchy anatomical distribution of atherosclerosis has been attributed to variation in haemodynamic wall shear stress (WSS). The consensus is that low WSS and a high Oscillatory Shear Index (OSI) trigger the disease. We found that atherosclerosis at aortic branch sites correlates threefold better with transverse WSS (transWSS), a metric which quantifies multidirectional near-wall flow. Coronary artery disease has greater clinical significance than aortic disease but computation of WSS metrics is complicated by the substantial vessel motion occurring during each cardiac cycle. Here we present the first comparison of the distribution of atherosclerosis with WSS metrics computed for moving coronary arteries.

METHODS

Maps of WSS metrics were computed using dynamic geometries reconstructed from angiograms of ten non-stenosed human right coronary arteries (RCAs). They were compared with maps of fatty streak prevalence derived from a previous study of 1852 RCAs.

RESULTS

Time average WSS (TAWSS), OSI, transWSS and the cross-flow index (CFI), a non-dimensional form of the transWSS, gave non-significant or significant but low spatial correlations with lesion prevalence. The highest correlation coefficient (0.71) was for the relative residence time (RRT), a metric that decreases with TAWSS and increases with OSI. The coefficient was not changed if RRT was calculated using CFI, which captures multidirectional WSS only, rather than OSI, which encompasses both multidirectional and oscillatory WSS.

CONCLUSION

Contrary to our earlier findings in the aorta, low WSS in combination with highly multidirectional flow correlates best with lesion location in the RCA, explaining approximately half of its anatomical variation.

Spatial patterns of high-risk biomechanical metrics in plaques with abnormal vs. normal physiological flow indices

BACKGROUND

Plaques associated with abnormally low physiological flow reserve indices are appropriate for percutaneous coronary intervention (PCI). However, recent trials demonstrate that PCI of ischemia-producing lesions does not reduce major adverse cardiac events (MACE). Low endothelial shear stress (ESS) or high ESS gradient (ESSG) are associated with MACE wherever they occur along the plaque. This study aims to determine the presence of high-risk ESS metrics in obstructive coronary plaques with high-risk (<0.80) vs. borderline-risk (0.80-0.89) vs. normal Instantaneous Wave-free Ratio (iFR) (>0.89).

METHODS

We included 50 coronary arteries (50 patients) with variable iFR values who underwent coronary angiography and optical coherence tomography (OCT), followed by 3D reconstruction and computational fluid dynamics calculations of ESS/ESSG. The cohort was divided into 3 groups: iFR < 0.80, iFR 0.80-0.89, and iFR > 0.89. Spatial distribution of ESS metrics was reported along the course of each plaque, and high-risk ESS metrics and their location were compared among the 3 iFR subgroups.

RESULTS

High-risk ESS features (Minimal ESS, Maximum ESSG) were similarly distributed along the course of the atherosclerotic plaque in the three iFR subgroups, both in absolute value and in location: Min ESS: 0.5 ± 0.3 vs. 0.4 ± 0.2 vs. 0.4 ± 0.2 Pa respectively (p = 0.60); Max ESSG any direction: 13.7 ± 9.4 vs. 10.4 ± 10.6 vs. 10.0 ± 7.8 Pa/mm respectively (p = 0.30). ESS metrics were spatially located up to ≥18 mm from the plaque minimal luminal area (MLA) in both directions.

CONCLUSION

High-risk ESS metrics are similarly observed in plaques with normal or abnormal iFR, both in absolute value and spatial location in reference to the MLA. Utilizing iFR to identify plaques likely to cause MACE would miss the majority of plaques mechanistically at high-risk to destabilize and cause future adverse cardiac events.

Algorithmic Generation of Parameterized Geometric Models of the Aortic Valve and Left Ventricle

Simulating the cardiac valves is one of the most complex tasks in cardiovascular modeling. As fluid-structure interaction simulations are highly computationally demanding, machine-learning techniques can be considered a good alternative. Nevertheless, it is necessary to design many aortic valve geometries to generate a training set. A method for the design of a synthetic database of geometric models is presented in this study. We suggest using synthetic geometries that enable the development of several aortic valve and left ventricular models in a range of sizes and shapes. In particular, we developed 22 variations of left ventricular geometries, including one original model, seven models with varying wall thicknesses, seven models with varying heights, and seven models with varying shapes. To guarantee anatomical accuracy and physiologically acceptable fluid volumes, these models were verified using actual patient data. Numerical simulations of left ventricle contraction and aortic valve leaflet opening/closing were performed to evaluate the electro-physiological potential distribution in the left ventricle and wall shear stress distribution in aortic valve leaflets. The proposed synthetic database aims to increase the predictive power of machine-learning models in cardiovascular research and, eventually, improve patient outcomes after aortic valve surgery.

Tension at the gate: sensing mechanical forces at the blood-brain barrier in health and disease

Microvascular brain endothelial cells tightly limit the entry of blood components and peripheral cells into the brain by forming the blood-brain barrier (BBB). The BBB is regulated by a cascade of mechanical and chemical signals including shear stress and elasticity of the adjacent endothelial basement membrane (BM). During physiological aging, but especially in neurological diseases including multiple sclerosis (MS), stroke, small vessel disease, and Alzheimer's disease (AD), the BBB is exposed to inflammation, rigidity changes of the BM, and disturbed cerebral blood flow (CBF). These altered forces lead to increased vascular permeability, reduced endothelial reactivity to vasoactive mediators, and promote leukocyte transmigration. Whereas the molecular players involved in leukocyte infiltration have been described in detail, the importance of mechanical signalling throughout this process has only recently been recognized. Here, we review relevant features of mechanical forces acting on the BBB under healthy and pathological conditions, as well as the endothelial mechanosensory elements detecting and responding to altered forces. We demonstrate the underlying complexity by focussing on the family of transient receptor potential (TRP) ion channels. A better understanding of these processes will provide insights into the pathogenesis of several neurological disorders and new potential leads for treatment.

Multimodal monitoring of cerebral perfusion in carotid endarterectomy patients: a computational fluid dynamics study

Objective

To evaluate postoperative cerebral perfusion changes and their influencing factors in carotid endarterectomy (CEA) patients by integrating multimodal monitoring methods, including cerebral regional oxygen saturation (rSO2), carotid ultrasound (CU), computed tomographic angiography (CTA), and computed tomographic perfusion imaging (CTP), with computational fluid dynamics (CFD) assessment.

Methods

We conducted a cohort study on patients with internal carotid artery (ICA) stenosis undergoing CEA at our institution. Pre- and postoperative assessments included CU, CTA, CTP, and rSO2 monitoring. Hemodynamic parameters recorded were mean flow velocity (MFV), peak systolic velocity (PSV), end diastolic velocity (EDV), resistance index (RI), rSO2, and cerebral blood flow (CBF). CFD quantified the total pressure (TP), wall shear stress (WSS), wall shear stress ratio (WSSR), and translesional pressure ratio (PR) of the ICA. Pearson correlation was used to analyze factors influencing cerebral perfusion changes. Multivariate logistic regression identified risk factors for cerebral hyperperfusion (CH). The predictive value of multimodal and single-modality monitoring for CH was evaluated using ROC curve analysis.

Results

Fifty-six patients were included, with nine developing postoperative CH. CU showed significant reductions in MFV, PSV, EDV, and RI of the ICA (p < 0.001). Ipsilateral rSO2 increased significantly (p = 0.013), while contralateral rSO2 showed no significant change (p = 0.861). CFD revealed significant decreases in TP, WSS, and WSSR (p < 0.001), along with a significant increase in PR (p < 0.001). Pearson analysis indicated that change rate of CBF (ΔCBF) positively correlated with ΔPR and ΔrSO2, and negatively correlated with ΔTP, ΔWSS, and Δ WSSR. Multivariate logistic regression identified preoperative WSSR (pre-WSSR) and ΔPR as risk factors for CH following CEA. Combined ΔPR, ΔrSO2, ΔMFV, and pre-WSSR had higher sensitivity and specificity than single-modality monitoring for predicting CH.

Conclusion

CFD-based multimodal monitoring effectively identified cerebral perfusion changes and risk factors for CH in CEA patients, with superior predictive accuracy compared to single-modality methods. Nevertheless, further validation is necessary to establish its clinical utility.

A Pseudo-Spectral Method for Wall Shear Stress Estimation from Doppler Ultrasound Imaging in Coronary Arteries

PURPOSE

The Wall Shear Stress (WSS) is the component tangential to the boundary of the normal stress tensor in an incompressible fluid, and it has been recognized as a quantity of primary importance in predicting possible adverse events in cardiovascular diseases, in general, and in coronary diseases, in particular. The quantification of the WSS in patient-specific settings can be achieved by performing a Computational Fluid Dynamics (CFD) analysis based on patient geometry, or it can be retrieved by a numerical approximation based on blood flow velocity data, e.g., ultrasound (US) Doppler measurements. This paper presents a novel method for WSS quantification from 2D vector Doppler measurements.

METHODS

Images were obtained through unfocused plane waves and transverse oscillation to acquire both in-plane velocity components. These velocity components were processed using pseudo-spectral differentiation techniques based on Fourier approximations of the derivatives to compute the WSS.

RESULTS

Our Pseudo-Spectral Method (PSM) is tested in two vessel phantoms, straight and stenotic, where a steady flow of 15 mL/min is applied. The method is successfully validated against CFD simulations and compared against current techniques based on the assumption of a parabolic velocity profile. The PSM accurately detected Wall Shear Stress (WSS) variations in geometries differing from straight cylinders, and is less sensitive to measurement noise. In particular, when using synthetic data (noise free, e.g., generated by CFD) on cylindrical geometries, the Poiseuille-based methods and PSM have comparable accuracy; on the contrary, when using the data retrieved from US measures, the average error of the WSS obtained with the PSM turned out to be 3 to 9 times smaller than that obtained by state-of-the-art methods.

CONCLUSION

The pseudo-spectral approach allows controlling the approximation errors in the presence of noisy data. This gives a more accurate alternative to the present standard and a less computationally expensive choice compared to CFD, which also requires high-quality data to reconstruct the vessel geometry.

Software for optimized virtual stenting of patient-specific coronary arteries reconstructed from angiography images

Detection of clinically relevant stenosis within coronary arteries as well as planning of treatment (stent implantation) are important topics in clinical cardiology. In this study a thorough methodology for virtual stenting assistance is proposed, that includes the 3D reconstruction of a patient-specific coronary artery from X-ray angiography images, hemodynamic simulations of blood flow, computation of a fractional flow reserve (FFR) equivalent, virtual stenting procedure and an optimization of the virtual stenting, by considering not only the value of computed FFR, but also the low and high WSS regions and the state of arterial wall after stenting. The evaluation of the proposed methodology is performed in two ways: the calculated values of FFR are compared with clinically measured values; and the results obtained for automated optimized virtual stenting are compared with virtual stenting performed manually by an expert clinician for the whole considered dataset. The agreement of the results in almost all cases demonstrates the accuracy of the proposed approach, and the small discrepancies only show the capabilities and benefits this approach can offer. The automated optimized virtual stenting technique can provide information about the most optimal stent position that ensures the maximum achievable FFR, while also considering the distribution of WSS and the state of arterial wall. The proposed methodology and developed software can therefore be used as a noninvasive method for planning of optimal patient-specific treatment strategies before invasive procedures and thus help to improve the clinical outcome of interventions and provide better treatment planning adapted to the particular patient.

Text mining of hypertension researches in the west Asia region: a 12-year trend analysis

More than half of the world population lives in Asia and hypertension (HTN) is the most prevalent risk factor found in Asia. There are numerous articles published about HTN in Eastern Mediterranean Region (EMRO) and artificial intelligence (AI) methods can analyze articles and extract top trends in each country. Present analysis uses Latent Dirichlet allocation (LDA) as an algorithm of topic modeling (TM) in text mining, to obtain subjective topic-word distribution from the 2790 studies over the EMRO. The period of checked studied is last 12 years and results of LDA analyses show that HTN researches published in EMRO discuss on changes in BP and the factors affecting it. Among the countries in the region, most of these articles are related to I.R Iran and Egypt, which have an increasing trend from 2017 to 2018 and reached the highest level in 2021. Meanwhile, Iraq and Lebanon have been conducting research since 2010. The EMRO word cloud illustrates 'BMI', 'mortality', 'age', and 'meal', which represent important indicators, dangerous outcomes of high BP, and gender of HTN patients in EMRO, respectively.

Comparison of stable carotid plaques in patients with mild-to-moderate carotid stenosis with vulnerable plaques in patients with significant carotid stenosis

To compare the characteristics of stable and vulnerable carotid plaques, and investigate the diagnostic performance of wall shear stress (WSS) based on magnetic resonance plaque imaging in carotid plaques. Retrospectively analyzed and divided 64 atherosclerotic plaques into stable carotid plaque groups with mild-to-moderate stenosis and vulnerable carotid plaque groups with significant stenosis. Computational fluid dynamics simulations were performed to calculate WSS parameters by using three-dimensional wall geometry based on high-resolution magnetic resonance plaque imaging of carotid bifurcation and patient specific boundary conditions obtained through color Doppler ultrasound. WSS parameters including upstream (WSSup), downstream (WSSdown), and core (WSScore) of plaque. The WSS parameters values were compared between the stable and vulnerable carotid plaque groups. Receiver operating characteristic curves and area under the curve (ROC-AUC) and Python were used to evaluate discriminative efficacy of WSS. WSSdown exhibited significant decrease in the vulnerable carotid plaque group (2.88 ± 0.41 Pa) compared to the stable carotid plaque group (4.47 ± 0.84 Pa) (P = .003). The difference of WSSup (3.28 ± 0.85 Pa vs 4.02 ± 0.74 Pa) and WSScore (1.12 ± 0.18 Pa vs 1.38 ± 0.38 Pa) between the two groups were also pronounced (P = .02, 0.01, respectively). The ROC-AUC values for WSSup, WSSdown, WSScore were 0.75 (95% CI, 0.58-0.93), 0.96 (95% CI, 0.79-1.14), 0.69 (95% CI, 0.56-0.83) respectively. When the value of WSSdown was 3.5 Pa, the sensitivity was 93.7% (95% CI, 76.1-111), specificity and accuracy was 87.5% (95% CI, 70.0-105), 88.4% (95% CI, 70.6-105) respectively. Notably, among these parameters, WSSdown demonstrated the highest discriminative efficiency with a F1 Score of 0.90, Diagnostic Odds Ratio of 105.0 and Matthews Correlation Coefficient of 0.81. Vulnerable carotid plaques with significant stenosis have lower WSS compared to stable plaques with mild-to-moderate stenosis, and downstream WSS showing the highest diagnostic efficacy.

The Association Between the Hemodynamics in Anomalous Origins of Coronary Arteries and Atherosclerosis: A Preliminary Case Study Based on Computational Fluid Dynamics

Patients with anomalous coronary artery origins (AOCA) exhibit a higher risk of atherosclerosis, where even minimal stenosis may lead to adverse cardiovascular events. However, the factors contributing to this heightened risk in AOCA patients remain unclear. This study aimed to investigate whether an AOCA patient is more prone to stenosis occurrence and its progression in view of hemodynamics. A patient whose left circumflex artery originated from the right coronary sinus with a mild stenosis in the left anterior descending (LAD) artery and a healthy individual were included in this study. Two additional models were developed by removing stenosis from the patient model and adding a corresponding stenosis to the healthy model. Additionally, the inlet flow waveforms for the left and right coronary arteries were swapped in both the patient and healthy models. Results indicated that the AOCA patient without stenosis demonstrated higher wall pressure (LAD: 95.57 ± 0.73 vs. 93.86 ± 0.50 mmHg; LCX: 94.97 ± 0.98 vs. 93.47 ± 0.56 mmHg; RCA: 96.23 ± 0.30 vs. 93.86 ± 0.46 mmHg) and TAWSS (LAD: 24.41 ± 19.53 vs. 13.82 ± 9.87 dyne/cm2, p < 0.0001; LCX: 27.21 ± 14.51 vs. 19.33 ± 8.78 dyne/cm2) compared to the healthy individual, with similar trends also observed in stenotic conditions. Significant changes in the LCX flow distribution were also noted under varying pulsatile conditions (LCX: 18.28% vs. 9.16%) compared to the healthy individual. The high-pressure, high-shear hemodynamic environment in AOCA patients predisposes them to atherosclerosis, and the unique geometry exacerbates hemodynamic abnormalities when stenosis occurs. Clinicians should closely monitor AOCA patients with stenosis to prevent adverse cardiovascular events.

Endothelial Shear Stress Metrics Associate With Proinflammatory Pathways at the Culprit Site of Coronary Erosion

Low endothelial shear stress (ESS) and associated adverse biomechanical features stimulate inflammation, contribute to atherogenesis, and predispose to coronary plaque disruption. The mechanistic links between adverse flow-related hemodynamics and inflammatory mediators implicated in plaque erosion, however, remain little explored. We investigated the relationship of high-risk ESS metrics to culprit lesion proinflammatory/proatherogenic cells and cytokines/chemokines implicated in coronary plaque erosion in patients with acute coronary syndromes. In eroded plaques, low ESS, high ESS gradient, and steepness of plaque topographical slope associated with increased numbers of local T cells and subsets (CD4+, CD8+, natural killer T cells) as well as inflammatory mediators (interleukin [IL]-6, macrophage inflammatory protein-1β, IL-1β, IL-2).

Shear stress is uncoupled from atheroprotective KLK10 in atherosclerotic plaques

BACKGROUND AND AIMS

Physiological shear stress promotes vascular homeostasis by inducing protective molecules in endothelial cells (EC). However, physiological shear stress has been linked to atherosclerosis progression in some individuals with heightened cardiovascular risk. To address this apparent paradox, we hypothesized that diseased arteries may exhibit reduced responsiveness to the protective effects of physiological shear stress. Consequently, we compared the transcriptome of EC exposed to physiological shear stress in healthy arteries versus atherosclerotic conditions.

METHODS

Employing 3D light sheet imaging and computational fluid dynamics, we identified NOS3 as a marker of physiological shear stress in both healthy and atherosclerotic murine arteries. Single-cell RNA sequencing was performed on EC from healthy (C57BL/6) mice, mildly diseased (Apoe-/- normal diet) mice, and highly diseased (Apoe-/- high fat diet) mice. The transcriptomes of Nos3high cells (exposed to physiological shear stress) were compared among the groups.

RESULTS

Nos3high EC were associated with several markers of physiological shear stress in healthy arteries. Clustering of Nos3high EC revealed 8 different EC subsets that varied in proportion between healthy and diseased arteries. Cluster-specific nested functional enrichment of gene ontology terms revealed that Nos3high EC in diseased arteries were enriched for inflammatory and apoptotic gene expression. These alterations were accompanied by changes in several mechanoreceptors, including the atheroprotective factor KLK10, which was enriched in Nos3high EC in healthy arteries but markedly reduced in severely diseased arteries.

CONCLUSIONS

Physiological shear stress is uncoupled from atheroprotective KLK10 within atherosclerotic plaques. This sheds light on the complex interplay between shear stress, endothelial function, and the progression of atherosclerosis in individuals at risk of cardiovascular complications.

Effects of statins in patients with coronary artery spasm: A nationwide population-based study

Controversies regarding the benefits of statin treatment on clinical outcomes in coronary artery spasm (CAS) without obstructive coronary artery disease (CAD) persist due to limited data. In this retrospective nationwide population-based cohort study from the Taiwan National Health Insurance Research Database during the period 2000-2012, the matched cohorts consisted of 12,000 patients with CAS. After propensity score matching with 1:1 ratio, 2216 patients were eligible for outcome analysis in either statin or nonstatin group, with the mean follow-up duration of 4.8 and 4.6 years, respectively. Statin users versus nonusers had a significantly reduced risk of major adverse cardiovascular events (MACEs) (6.7% vs. 9.5%, hazard ratio [HR] 0.68; 95% confidence interval [CI] 0.55-0.84) and all-cause mortality (6.0% vs. 7.6%; HR 0.77; 95% CI 0.61-0.96). While the results of MACEs were mainly contributed by cardiovascular death (1.9% vs. 3.2%; HR 0.56; 95% CI 0.38-0.83) and ischemic stroke (3.8% vs. 5.4%; subdistribution HR 0.69; 95% CI 0.52-0.91), they were primarily driven by reductions in ischemic but not hemorrhagic stroke. The benefit of statins was significantly pronounced in patients with hypertension and diabetes. Nevertheless, the effect on MACEs was consistent irrespective of age, sex, dyslipidemia, and mental disorder. Statins significantly reduced the risk of MACEs and all-cause mortality in CAS patients. The benefit of statin therapy in reducing MACEs appeared to be linear, with greater risk reduction with higher doses and longer duration without upper threshold, reflecting the dose-dependent relationship of statins with MACEs in CAS patients.

Shear Stress Induces a Time-Dependent Inflammatory Response in Human Monocyte-Derived Macrophages

Macrophages are innate immune cells that are known for their extreme plasticity, enabling diverse phenotypes that lie on a continuum. In a simplified model, they switch between pro-inflammatory (M1) and anti-inflammatory (M2) phenotypes depending on surrounding microenvironmental cues, which have been implicated in disease outcomes. Although considerable research has been focused on macrophage response to biochemical cues and mechanical signals, there is a scarcity of knowledge surrounding their behavior in response to shear stress. In this study, we applied varying magnitudes of shear stress on human monocyte-derived macrophages (MDMs) using a cone-and-plate viscometer and evaluated changes in morphology, gene expression, protein expression, and cytokine secretion over time. MDMs exposed to shear stress exhibited a rounder morphology compared to statically-cultured controls. RT-qPCR results showed significant upregulation of TNF-α, and analysis of cytokine release revealed increased secretion of IL-8, IL-18, fractalkine, and other chemokines. The upregulation of pro-inflammatory factors was evident with both increasing magnitudes of shear and time. Taken together, these results indicate that prolonged shear exposure induced a pro-inflammatory phenotype in human MDMs. These findings have implications for medical technology development, such as in situ vascular graft design wherein macrophages are exposed to shear and have been shown to affect graft resorption, and in delineating disease pathophysiology, for example to further illuminate the role of macrophages in atherosclerosis where shear is directly related to disease outcome.

Advanced Applications of Nanomaterials in Atherosclerosis Diagnosis and Treatment: Challenges and Future Prospects

Atherosclerosis-induced coronary artery disease is a major cause of cardiovascular mortality. Clinically, conservative treatment strategies for atherosclerosis still focus on lifestyle interventions and the use of lipid-lowering and anticoagulant medications. Despite achieving some therapeutic effects, these approaches are limited by low bioavailability, long intervention periods, and significant side effects. With the advancement of nanotechnology, nanomaterials have demonstrated extraordinary potential in the biomedical field. Their excellent biocompatibility, surface modifiability, and high targeting capability not only enable efficient diagnosis of plaque progression but also allow precise drug delivery within atherosclerotic plaques, significantly enhancing drug bioavailability and reducing systemic side effects. Here, we systematically review the current research progress of nanomaterials in the field of atherosclerosis to summarize not only the types of nanomaterials but also their applications in both the diagnosis and treatment of atherosclerosis. Notably, in the context of plaque therapy, we provide a comprehensive overview of current nanomaterial applications based on their targeted therapeutic systems for different cell types within plaques. Additionally, we address the persistent challenge of clinical translation of nanomaterials by summarizing current issues and providing directions for innovation and improvement in nanomaterial design. Overall, we believe that this review systematically summarizes the applications and challenges of biomedical nanomaterials in atherosclerosis diagnosis and therapy, thereby offering insights and references for the development of therapeutic materials for atherosclerosis.

Low shear-induced fibrillar fibronectin: comparative analyses of morphologies and cellular effects on bovine aortic endothelial cell adhesion and proliferation

Wall shear stress (WSS) is a critical factor in vascular biology, and both high and low WSS are implicated in atherosclerosis. Fibronectin (FN) is a key extracellular matrix protein that plays an important role in cell activities. Under high shear stress, plasma FN undergoes fibrillogenesis; however, its behavior under low shear stress remains unclear. This study aimed to investigate the formation ofin vitrocell-free fibrillar FN (FFN) under low shear rate conditions and its effect on bovine aortic endothelial cell behavior. FN (500µg ml-1) was perfused through slide chambers at three flow rates (0.16 ml h-1, 0.25 ml h-1, and 0.48 ml h-1), corresponding to low shear rates of 0.35 s-1, 0.55 s-1, and 1.05 s-1, respectively, for 4 h at room temperature. The formed FN matrices were observed using fluorescence microscopy and scanning electron microscopy. Under low shear rates, distinct FN matrix structures were observed. FFN0.48 formed immense fibrils with smooth surfaces, FFN0.25 formed a matrix with a rough surface, and FFN16 exhibited nodular structures. FFN0.25 supported cell activities to a greater extent than native FN and other FFN surfaces. Our study suggests that abnormally low shear conditions impact FN structure and function and enhance the understanding of FN fibrillogenesis in vascular biology, particularly in atherosclerosis.

Improvement of the outcome of the saphenous vein graft when connected to the internal thoracic artery

Background

Since 2000, we have been grafting the right coronary artery system (RCAs) using the proximal portion of the right internal thoracic artery (RITA) as the inflow of the saphenous vein graft (SVG) to increase the number of patients undergoing beating heart complete myocardial revascularization.

Methods

From 2000 to 2022, 928 consecutive patients underwent SVG on the RCAs. In 546 patients (58.8%), the inflow was the RITA (I-graft group), and in 382 patients (41.2%), the inflow was the aorta (Ao-graft group). The inclusion criteria were age ≤75 years, ejection fraction >35%, only one SVG per patient, bilateral internal thoracic arteries as a Y-graft on the left system (three-vessel disease, n = 817, 88.0%) or left internal thoracic artery on the left anterior descending artery and RITA + SVG on the RCAs (two-vessel disease, n = 111, 12.0%). Propensity matching identified 306 patients per group. After a median follow-up of 8 (5-10) years, graft patency was assessed by coronary computed tomographic angiography in 132 patients (64 in the I-graft group and 68 in the Ao-graft group).

Results

Early results were similar in both groups. The I-graft group had higher 10-year survival and freedom from main adverse cardiac events (90.0 ± 2.0 vs. 80.6 ± 3.8, p = 0.0162, and 81.3 ± 2.7 vs. 64.7 ± 5.6, p = 0.0206, respectively). When RITA was the inflow, SVG had a higher estimated 10-year patency rate (82.8% ± 6.5 vs. 58.8% ± 7.4, p = 0.0026) and a smaller inner lumen diameter (2.7 ± 0.4 vs. 3.4 ± 0.6 mm, p < 0.0001).

Conclusion

When the inflow is the RITA, SVG grafted to the RCAs (I-graft) may result in a higher patency rate and better outcome than when the inflow is the ascending aorta (Ao-graft). The continuous supply of nitric oxide by RITA may be the cause of the higher patency rate of the I-graft, which can behave like an arterial conduit.

Patient-Specific Numerical Simulations of Coronary Artery Hemodynamics and Biomechanics: A Pathway to Clinical Use

PURPOSE

Numerical models that simulate the behaviors of the coronary arteries have been greatly improved by the addition of fluid-structure interaction (FSI) methods. Although computationally demanding, FSI models account for the movement of the arterial wall and more adequately describe the biomechanical conditions at and within the arterial wall. This offers greater physiological relevance over Computational Fluid Dynamics (CFD) models, which assume the walls do not move or deform. Numerical simulations of patient-specific cases have been greatly bolstered by the use of imaging modalities such as Computed Tomography Angiography (CTA), Magnetic Resonance Imaging (MRI), Optical Coherence Tomography (OCT), and Intravascular Ultrasound (IVUS) to reconstruct accurate 2D and 3D representations of artery geometries. The goal of this study was to conduct a comprehensive review on CFD and FSI models on coronary arteries, and evaluate their translational potential.

METHODS

This paper reviewed recent work on patient-specific numerical simulations of coronary arteries that describe the biomechanical conditions associated with atherosclerosis using CFD and FSI models. Imaging modality for geometry collection and clinical applications were also discussed.

RESULTS

Numerical models using CFD and FSI approaches are commonly used to study biomechanics within the vasculature. At high temporal and spatial resolution (compared to most cardiac imaging modalities), these numerical models can generate large amount of biomechanics data.

CONCLUSIONS

Physiologically relevant FSI models can more accurately describe atherosclerosis pathogenesis, and help to translate biomechanical assessment to clinical evaluation.

Exploring the relationship between hemodynamics and the immune microenvironment in carotid atherosclerosis: Insights from CFD and CyTOF technologies

Carotid atherosclerosis is a major cause of stroke. Hemodynamic forces, such as shear stress and oscillatory shear, play an important role in the initiation and progression of atherosclerosis. The alteration of the immune microenvironment is the fundamental pathological mechanism by which diverse external environmental factors impact the formation and progression of plaques. However, Current research on the relationship between hemodynamics and immunity in atherosclerosis still lack of comprehensive understanding. In this study, we combined computational fluid dynamics (CFD) and Mass cytometry (CyTOF) technologies to explore the changes in the immune microenvironment within plaques under different hemodynamic conditions. Our results indicated that neutrophils were enriched in adverse flow environments. M2-like CD163+CD86+ macrophages were predominantly enriched in high WSS and low OSI environments, while CD163-CD14+ macrophages were enriched in low WSS and high OSI environments. Functional analysis further revealed T cell pro-inflammatory activation and dysregulation in modulation, along with an imbalance in M1-like/M2-like macrophages, suggesting their potential involvement in the progression of atherosclerotic lesions mediated by adverse flow patterns. Our study elucidated the potential mechanisms by which hemodynamics regulated the immune microenvironment within plaques, providing intervention targets for future precision therapies.

PCSK9 expression in fibrous cap possesses a marker for rupture in advanced plaque

BACKGROUND

To date, PCSK9 inhibitors are well known for eliminating cardiac and cerebral artery ischemia events by lowering the serum lipid level. However, the pathophysiological value of in-plaque PCSK9 expression is still unclear.

METHODS

Advanced plaques removed by carotid endarterectomy were sectioned and stained to identify the PCSK9 expression pattern and its co-expression with rupture-relevant markers. To investigate the correlation of PCSK9 expression with regional blood shear flow, hemodynamic characteristics were analyzed using computational fluid dynamics, and representative parameters were compared between PCSK9 positive and negative staining plaques. To explore this phenomenon in vitro, human aortic vascular smooth muscle cells were used to overexpress and knock down PCSK9. The impacts of PCSK9 modulations on mechanical sensor activity were testified by western blot and immunofluorescence. Real-time polymerase chain reaction was used to evaluate the transcription levels of downstream rupture-prone effectors.

RESULTS

PCSK9 distribution in plaque preferred cap and shoulder regions, residing predominantly in smooth muscle actin-positive cells. Cap PCSK9 expression correlated with fibrous cap thickness negatively and co-expressed with MMP-9, both pointing to the direction of plaque rupture. A hemodynamic profile indicated a rupture-prone feature of cap PCSK9 expression. In vitro, overexpression and knockdown of PCSK9 in human aortic vascular smooth muscle cells has positive modulation on mechanical sensor Yes-associated protein 1 (YAP) activity and transcription levels of its downstream rupture-prone effectors. Serial section staining verified in situ colocalization among PCSK9, YAP, and downstream effectors.

CONCLUSIONS

Cap PCSK9 possesses a biomarker for rupture risk, and its modulation may lead to a novel biomechanical angle for plaque interventions.

Advances in the Computational Assessment of Disturbed Coronary Flow and Wall Shear Stress: A Contemporary Review

Coronary artery blood flow is influenced by various factors including vessel geometry, hemodynamic conditions, timing in the cardiac cycle, and rheological conditions. Multiple patterns of disturbed coronary flow may occur when blood flow separates from the laminar plane, associated with inefficient blood transit, and pathological processes modulated by the vascular endothelium in response to abnormal wall shear stress. Current simulation techniques, including computational fluid dynamics and fluid-structure interaction, can provide substantial detail on disturbed coronary flow and have advanced the contemporary understanding of the natural history of coronary disease. However, the clinical application of these techniques has been limited to hemodynamic assessment of coronary disease severity, with the potential to refine the assessment and management of coronary disease. Improved computational efficiency and large clinical trials are required to provide an incremental clinical benefit of these techniques beyond existing tools. This contemporary review is a clinically relevant overview of the disturbed coronary flow and its associated pathological consequences. The contemporary methods to assess disturbed flow are reviewed, including clinical applications of these techniques. Current limitations and future opportunities in the field are also discussed.

Predicting coronary artery occlusion risk from noninvasive images by combining CFD-FSI, cGAN and CNN

Wall Shear Stress (WSS) is one of the most important parameters used in cardiovascular fluid mechanics, and it provides a lot of information like the risk level caused by any vascular occlusion. Since WSS cannot be measured directly and other available relevant methods have issues like low resolution, uncertainty and high cost, this study proposes a novel method by combining computational fluid dynamics (CFD), fluid-structure interaction (FSI), conditional generative adversarial network (cGAN) and convolutional neural network (CNN) to predict coronary artery occlusion risk using only noninvasive images accurately and rapidly. First, a cGAN model called WSSGAN was developed to predict the WSS contours on the vessel wall by training and testing the model based on the calculated WSS contours using coupling CFD-FSI simulations. Then, an 11-layer CNN was used to classify the WSS contours into three grades of occlusions, i.e. low risk, medium risk and high risk. To verify the proposed method for predicting the coronary artery occlusion risk in a real case, the patient's Magnetic Resonance Imaging (MRI) images were converted into a 3D geometry for use in the WASSGAN model. Then, the predicted WSS contours by the WSSGAN were entered into the CNN model to classify the occlusion grade.

Establishing the longitudinal hemodynamic mapping framework for wearable-driven coronary digital twins

Understanding the evolving nature of coronary hemodynamics is crucial for early disease detection and monitoring progression. We require digital twins that mimic a patient's circulatory system by integrating continuous physiological data and computing hemodynamic patterns over months. Current models match clinical flow measurements but are limited to single heartbeats. To this end, we introduced the longitudinal hemodynamic mapping framework (LHMF), designed to tackle critical challenges: (1) computational intractability of explicit methods; (2) boundary conditions reflecting varying activity states; and (3) accessible computing resources for clinical translation. We show negligible error (0.0002-0.004%) between LHMF and explicit data of 750 heartbeats. We deployed LHMF across traditional and cloud-based platforms, demonstrating high-throughput simulations on heterogeneous systems. Additionally, we established LHMFC, where hemodynamically similar heartbeats are clustered to avoid redundant simulations, accurately reconstructing longitudinal hemodynamic maps (LHMs). This study captured 3D hemodynamics over 4.5 million heartbeats, paving the way for cardiovascular digital twins.

A new understanding of coronary curvature and haemodynamic impact on the course of plaque onset and progression

The strong link between atherosclerosis and luminal biomechanical stresses is well established. Yet, this understanding has not translated into preventative coronary diagnostic imaging, particularly due to the under-explored role of coronary anatomy and haemodynamics in plaque onset, which we aim to address with this work. The left coronary trees of 20 non-stenosed (%diameter stenosis [%DS] = 0), 12 moderately (0 < %DS < 70) and 7 severely (%DS ≥ 70) stenosed cases were dissected into bifurcating and non-bifurcating segments for whole-tree and segment-specific comparisons, correlating nine three-dimensional coronary anatomical features, topological shear variation index (TSVI) and luminal areas subject to low time-average endothelial shear stress (%LowTAESS), high oscillatory shear index (%HighOSI) and high relative residence time (%HighRRT). We found that TSVI is the only metric consistently differing between non-stenosed and stenosed cases across the whole tree, bifurcating and non-bifurcating segments (p < 0.002, AUC = 0.876), whereas average curvature and %HighOSI differed only for the whole trees (p < 0.024) and non-bifurcating segments (p < 0.027), with AUC > 0.711. Coronary trees with moderate or severe stenoses differed only in %LowTAESS (p = 0.009) and %HighRRT (p = 0.012). This suggests TSVI, curvature and %HighOSI are potential factors driving plaque onset, with greater predictive performance than the previously recognized %LowTAESS and %HighRRT, which appears to play a role in plaque progression.

Estimation of Serum Malondialdehyde (a Marker of Oxidative Stress) as a Predictive Biomarker for the Severity of Coronary Artery Disease (CAD) and Cardiovascular Outcomes

Background Coronary artery disease (CAD) is influenced by oxidative stress, which is a critical yet often overlooked factor in disease progression. While traditional biomarkers such as cholesterol levels and blood pressure are commonly used, they do not fully capture oxidative damage. Malondialdehyde (MDA), a byproduct of lipid peroxidation, offers additional insights into oxidative stress and CAD severity. Unlike conventional markers, such as low-density lipoprotein (LDL) cholesterol, which primarily reflects lipid levels, and high-sensitivity C-reactive protein (hs-CRP), which indicates inflammation, MDA directly measures oxidative damage. This makes MDA a potentially valuable complement to these traditional biomarkers, providing a more nuanced understanding of CAD risk. Despite its potential, the role of MDA in clinical assessments remains underexplored. This study aims to address this gap by evaluating MDA's effectiveness as a complementary biomarker, enhancing the assessment of CAD risk and progression beyond what is provided by existing markers. Objective This study aims to assess serum MDA levels in relation to CAD severity to explore its potential as a non-invasive biomarker for disease progression and cardiovascular outcomes. Methodology This cross-sectional study was conducted at the Department of Cardiology, Mardan Medical Complex Teaching Hospital, Pakistan, from June 2023 to May 2024. Patients were divided into different groups with varying severity of CAD. The one-way ANOVA was used to assess differences among groups, and Pearson's correlation coefficient explored relationships between MDA and all study variables. Simple linear regression analyzed associations between MDA levels, patient groups, and other variables, controlling for covariates. MDA's potential as a predictive biomarker was assessed through ROC curve analysis, with statistical significance set at a p-value < 0.05. Results A total of 133 patients were included in the study, categorized based on CAD severity into mild (n=71), moderate (n=39), and severe (n=23) groups. Serum MDA levels significantly increased with the severity of CAD. Specifically, MDA levels were 116.61 ± 41.95 in the mild group, 253.45 ± 180.29 in the moderate group, and peaked at 459.91 ± 149.80 in the severe group. The differences in MDA levels among these groups were statistically significant (p < 0.01), supporting the association between higher MDA levels and increased CAD severity. Factors such as BMI, heart rate, blood pressure, and smoking status also significantly influenced MDA levels. Receiver operating characteristic (ROC) curve analysis demonstrated high diagnostic accuracy of MDA for assessing CAD severity, with area under the curve (AUC) values of 0.81 for moderate and 0.94 for severe CAD. Comorbid conditions such as diabetes mellitus were associated with elevated MDA levels. Conclusion Elevated serum MDA serves as a reliable, non-invasive biomarker for predicting CAD severity, with potential applications in clinical risk assessment and management strategies. By identifying patients with elevated oxidative stress early, clinicians can implement timely interventions, potentially slowing disease progression and improving outcomes.

Hemodynamic influence of mild stenosis morphology in different coronary arteries: a computational fluid dynamic modelling study

Introduction: Mild stenosis [degree of stenosis (DS) < 50%] is commonly labeled as nonobstructive lesion. Some lesions remain stable for several years, while others precipitate acute coronary syndromes (ACS) rapidly. The causes of ACS and the factors leading to diverse clinical outcomes remain unclear. Method: This study aimed to investigate the hemodynamic influence of mild stenosis morphologies in different coronary arteries. The stenoses were modeled with different morphologies based on a healthy individual data. Computational fluid dynamics analysis was used to obtain hemodynamic characteristics, including flow waveforms, fractional flow reserve (FFR), flow streamlines, time-average wall shear stress (TAWSS), and oscillatory shear index (OSI). Results: Numerical simulation indicated significant hemodynamic differences among different DS and locations. In the 20%-30% range, significant large, low-velocity vortexes resulted in low TAWSS (<4 dyne/cm2) around stenoses. In the 30%-50% range, high flow velocity due to lumen area reduction resulted in high TAWSS (>40 dyne/cm2), rapidly expanding the high TAWSS area (averagely increased by 0.46 cm2) in left main artery and left anterior descending artery (LAD), where high OSI areas remained extensive (>0.19 cm2). Discussion: While mild stenosis does not pose any immediate ischemic risk due to a FFR > 0.95, 20%-50% stenosis requires attention and further subdivision based on location is essential. Rapid progression is a danger for lesions with 20%-30% DS near the stenoses and in the proximal LAD, while lesions with 30%-50% DS can cause plaque injury and rupture. These findings support clinical practice in early assessment, monitoring, and preventive treatment.

Computed Tomography Angiography Identified High-Risk Coronary Plaques: From Diagnosis to Prognosis and Future Management

CT angiography has become, in recent years, a main evaluating modality for patients with coronary artery disease (CAD). Recent advancements in the field have allowed us to identity not only the presence of obstructive disease but also the characteristics of identified lesions. High-risk coronary atherosclerotic plaques are identified in CT angiographies via a number of specific characteristics and may provide prognostic and therapeutic implications, aiming to prevent future ischemic events via optimizing medical treatment or providing coronary interventions. In light of new evidence evaluating the safety and efficacy of intervening in high-risk plaques, even in non-flow-limiting disease, we aim to provide a comprehensive review of the diagnostic algorithms and implications of plaque vulnerability in CT angiography, identify any differences with invasive imaging, analyze prognostic factors and potential future therapeutic options in such patients, as well as discuss new frontiers, including intervening in non-flow-limiting stenoses and the role of CT angiography in patient stratification.

Myocardial Bridge and Atherosclerosis, an Intimal Relationship

PURPOSE OF REVIEW

This review investigates the relationship between myocardial bridges (MBs), intimal thickening in coronary arteries, and Atherosclerotic cardiovascular disease. It focuses on the role of mechanical forces, such as circumferential strain, in arterial wall remodeling and aims to clarify how MBs affect coronary artery pathology.

REVIEW FINDINGS

MBs have been identified as influential in modulating coronary artery intimal thickness, demonstrating a protective effect against thickening within the MB segment and an increase in thickness proximal to the MB. This is attributed to changes in mechanical stress and hemodynamics. Research involving arterial hypertension models and vein graft disease has underscored the importance of circumferential strain in vascular remodeling and intimal hyperplasia. Understanding the complex dynamics between MBs, mechanical strain, and vascular remodeling is crucial for advancing our knowledge of coronary artery disease mechanisms. This could lead to improved management strategies for cardiovascular diseases, highlighting the need for further research into MB-related vascular changes.

A parametric study of the effect of 3D plaque shape on local hemodynamics and implications for plaque instability

The vast majority of heart attacks occur when vulnerable plaques rupture, releasing their lipid content into the blood stream leading to thrombus formation and blockage of a coronary artery. Detection of these unstable plaques before they rupture remains a challenge. Hemodynamic features including wall shear stress (WSS) and wall shear stress gradient (WSSG) near the vulnerable plaque and local inflammation are known to affect plaque instability. In this work, a computational workflow has been developed to enable a comprehensive parametric study detailing the effects of 3D plaque shape on local hemodynamics and their implications for plaque instability. Parameterized geometric 3D plaque models are created within a patient-specific coronary artery tree using a NURBS (non-uniform rational B-splines)-based vascular modeling pipeline. Realistic blood flow features are simulated by using a Navier-Stokes solver within an isogeometric finite-element analysis framework. Near wall hemodynamic quantities such as WSS and WSSG are quantified, and vascular distribution of an inflammatory marker (VCAM-1) is estimated. Results show that proximally skewed eccentric plaques have the most vulnerable combination of high WSS and high positive spatial WSSG, and the presence of multiple lesions increases risk of rupture. The computational tool developed in this work, in conjunction with clinical data, -could help identify surrogate markers of plaque instability, potentially leading to a noninvasive clinical procedure for the detection of vulnerable plaques before rupture.

Coronary computed tomographic angiography-derived anatomic and hemodynamic plaque characteristics in prediction of cardiovascular events

This study investigated the association of anatomic and hemodynamic plaque characteristics based on deep learning coronary computed tomography angiography (CCTA) with high-risk plaques that caused subsequent major adverse cardiovascular events (MACE). A retrospective analysis was conducted on patients who underwent CCTA between 1 month and 3 years prior to the occurrence of a MACE. Deep learning and computational fluid dynamics algorithms based on CCTA were applied to extract adverse plaque characteristics (low-attenuation plaque, positive remodeling, napkin-ring sign, and spotty calcification), and hemodynamic parameters (fractional flow reserve derived by coronary computed tomographic angiography [FFRCT], change in FFRCT across the lesion [△FFRCT], wall shear stress [WSS], and axial plaque stress [APS]). Correlation analysis, logistic regression, and Cox proportional risk analysis were conducted to understand the relationship between these measures and the occurrence of MACE and assess the value of hemodynamic parameters in predicting the incidence of MACE events and their prognosis. Our study included 86 patients with a total of 134 vessels exhibiting plaque formation and 83 culprit vessels with a subsequent coronary event. Culprit vessels had percent diameter stenosis [%DS] (0.54 ± 0.16 vs. 0.62 ± 0.13, P = 0.003), larger non-calcified plaque volume (45.8 vs. 101.7, P < 0.001), larger low-attenuation plaque volume (3.6 vs. 14.5, P < 0.001), more lesions with ≥ 3 adverse plaque characteristics (APC) (4 vs.26, P = 0.002), and worse hemodynamic features of adverse plaque. FFRCT demonstrated better visualization of maximum achievable flow in the presence of coronary stenosis and better correlation with the stenosis severity, while maximum of wall shear stress (WSSmax) was highly correlated with low-attenuation plaques and APC. The inclusion of hemodynamic parameters improved the efficacy of the predictive model, and a high WSS suggested a higher probability of MACE. Hemodynamic parameters based on CCTA are significantly correlated with plaque morphology. Importantly, integrating CCTA-derived parameters can refine the predictive performance of MACE occurrence.

Biomechanical factors and atherosclerosis localization: insights and clinical applications

Although the entire vascular bed is constantly exposed to the same risk factors, atherosclerosis manifests a distinct intra-individual pattern in localization and progression within the arterial vascular bed. Despite shared risk factors, the development of atherosclerotic plaques is influenced by physical principles, anatomic variations, metabolic functions, and genetic pathways. Biomechanical factors, particularly wall shear stress (WSS), play a crucial role in atherosclerosis and both low and high WSS are associated with plaque progression and heightened vulnerability. Low and oscillatory WSS contribute to plaque growth and arterial remodeling, while high WSS promotes vulnerable changes in obstructive coronary plaques. Axial plaque stress and plaque structural stress are proposed as biomechanical indicators of plaque vulnerability, representing hemodynamic stress on stenotic lesions and localized stress within growing plaques, respectively. Advancements in imaging and computational fluid dynamics techniques enable a comprehensive analysis of morphological and hemodynamic properties of atherosclerotic lesions and their role in plaque localization, evolution, and vulnerability. Understanding the impact of mechanical forces on blood vessels holds the potential for developing shear-regulated drugs, improving diagnostics, and informing clinical decision-making in coronary atherosclerosis management. Additionally, Computation Fluid Dynamic (CFD) finds clinical applications in comprehending stent-vessel dynamics, complexities of coronary bifurcations, and guiding assessments of coronary lesion severity. This review underscores the clinical significance of an integrated approach, concentrating on systemic, hemodynamic, and biomechanical factors in atherosclerosis and plaque vulnerability among patients with coronary artery disease.

Impact of endothelial shear stress on coronary atherosclerotic plaque progression and composition: A meta-analysis and systematic review

BACKGROUND AND AIMS

Intracoronary pressure gradients and translesional flow patterns have been correlated with coronary plaque progression and lesion destabilization. In this study, we aimed to determine the relationship between endothelial shear stress and plaque progression and to evaluate the effect of shear forces on coronary plaque features.

METHODS

A systematic review was conducted in medical on-line databases. Selected were studies including human participants who underwent coronary anatomy assessment with computational fluid dynamics (CFD)-based wall shear stress (WSS) calculation at baseline with anatomical evaluation at follow-up. A total of six studies were included for data extraction and analysis.

RESULTS

The meta-analysis encompassed 31'385 arterial segments from 136 patients. Lower translesional WSS values were significantly associated with a reduction in lumen area (mean difference -0.88, 95% CI -1.13 to -0.62), an increase in plaque burden (mean difference 4.32, 95% CI 1.65 to 6.99), and an increase in necrotic core area (mean difference 0.02, 95% CI 0.02 to 0.03) at follow-up imaging. Elevated WSS values were associated with an increase in lumen area (mean difference 0.78, 95% CI 0.34 to 1.21) and a reduction in both fibrofatty (mean difference -0.02, 95% CI -0.03 to -0.01) and fibrous plaque areas (mean difference -0.03, 95% CI -0.03 to -0.03).

CONCLUSION

This meta-analysis shows that WSS parameters were related to vulnerable plaque features at follow-up. These results emphasize the impact of endothelial shear forces on coronary plaque growth and composition. Future studies are warranted to evaluate the role of WSS in guiding clinical decision-making.

Integrating Computational and Biological Hemodynamic Approaches to Improve Modeling of Atherosclerotic Arteries

Atherosclerosis is the primary cause of cardiovascular disease, resulting in mortality, elevated healthcare costs, diminished productivity, and reduced quality of life for individuals and their communities. This is exacerbated by the limited understanding of its underlying causes and limitations in current therapeutic interventions, highlighting the need for sophisticated models of atherosclerosis. This review critically evaluates the computational and biological models of atherosclerosis, focusing on the study of hemodynamics in atherosclerotic coronary arteries. Computational models account for the geometrical complexities and hemodynamics of the blood vessels and stenoses, but they fail to capture the complex biological processes involved in atherosclerosis. Different in vitro and in vivo biological models can capture aspects of the biological complexity of healthy and stenosed vessels, but rarely mimic the human anatomy and physiological hemodynamics, and require significantly more time, cost, and resources. Therefore, emerging strategies are examined that integrate computational and biological models, and the potential of advances in imaging, biofabrication, and machine learning is explored in developing more effective models of atherosclerosis.

Hemodynamics comparison of an hour-long rest and activity state data in a human coronary digital twin

Although it is well established that hemodynamics can significantly influence the location and progression of cardiovascular disease (CVD), and 3D blood flow metrics are recognized as potential diagnostic indicators of these diseases, the dynamics of these metrics over time and their variation at different activity levels are not well understood. A relevant example is the impact of exercise on the vascular system over extended periods. Although exercise is widely recognized as a preventive measure of heart disease, the specifics of how activity levels and subsequent alterations in blood flow contribute to the mechanisms that drive CVD remain unclear. In this study, we used a digital coronary twin to establish a longitudinal hemodynamic map (LHM) of the rest and exercise states. An hour-long dataset for both the rest and exercise states, acquired from a wearable device for a single patient, was used to drive a complex 3D fluid dynamics simulation. Hemodynamic metrics such as maximum velocity, average velocity, maximum wall shear stress, average wall shear stress, time-averaged wall shear stress, and pressure gradient were compared between the two states. This analysis represents an initial step toward understanding how long-term exercise regimens can influence hemodynamic changes and potentially reduce the risk of cardiovascular disease. Our findings revealed that the maximum wall shear stress exhibited the highest sensitivity to changes in activity level, while the pressure gradient showed the least variability. This study contributes significantly to quantifying how 3D blood flow metrics differ between rest and active states, providing valuable insight regarding exercise-induced hemodynamic alterations and their potential role in mitigating CVD risk.

Plaque Ruptures Are Related to High Plaque Stress and Strain Conditions: Direct Verification by Using In Vivo OCT Rupture Data and FSI Models

BACKGROUND

While it has been hypothesized that high plaque stress and strain may be related to plaque rupture, its direct verification using in vivo coronary plaque rupture data and full 3-dimensional fluid-structure interaction models is lacking in the current literature due to difficulty in obtaining in vivo plaque rupture imaging data from patients with acute coronary syndrome. This case-control study aims to use high-resolution optical coherence tomography-verified in vivo plaque rupture data and 3-dimensional fluid-structure interaction models to seek direct evidence for the high plaque stress/strain hypothesis.

METHODS

In vivo coronary plaque optical coherence tomography data (5 ruptured plaques, 5 no-rupture plaques) were acquired from patients using a protocol approved by the local institutional review board with informed consent obtained. The ruptured caps were reconstructed to their prerupture morphology using neighboring plaque cap and vessel geometries. Optical coherence tomography-based 3-dimensional fluid-structure interaction models were constructed to obtain plaque stress, strain, and flow shear stress data for comparative analysis. The rank-sum test in the nonparametric test was used for statistical analysis.

RESULTS

Our results showed that the average maximum cap stress and strain values of ruptured plaques were 142% (457.70 versus 189.22 kPa; P=0.0278) and 48% (0.2267 versus 0.1527 kPa; P=0.0476) higher than that for no-rupture plaques, respectively. The mean values of maximum flow shear stresses for ruptured and no-rupture plaques were 145.02 dyn/cm2 and 81.92 dyn/cm2 (P=0.1111), respectively. However, the flow shear stress difference was not statistically significant.

CONCLUSIONS

This preliminary case-control study showed that the ruptured plaque group had higher mean maximum stress and strain values. Due to our small study size, larger scale studies are needed to further validate our findings.