Different Degrees Of Stenosis Research Articles

ASSESSMENT OF GROWTH AND RUPTURE OF CAROTID ATHEROSCLEROSIS AND PLAQUE WITH DIFFERENT DEGREES OF STENOSIS

In this study, the growth and rupture of plaque were investigated to predict the development of carotid atherosclerosis and plaque. Realistic 3D models of multi-component plaque and carotid artery were established in healthy, mild, moderate, and severe stenosis. Fluid–structure interaction (FSI) simulations were performed on these models, and the wall shear stress (WSS), time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), relative residence time (RRT), and wall tensile stress (WTS) in a natural cardiac cycle were analyzed to assess the epidermal rupture, growth tendency, and internal rupture of plaques in a natural state. Results show that in severe stenosis, the WSS at the stenosis sites exceeds the threshold of rupture during almost the entire cardiac cycle, thus causing an epidermal injury, bringing about plaque detachment and thrombosis. TAWSS decreased and OSI and RRT increased in the bifurcation region and the downstream region of the plaque. The deposition is more likely to occur in these regions. A higher degree of stenosis will increase the OSI and RRT in the downstream region of the plaque, leading to continuous deterioration of the plaque, while the degree of stenosis has little effect on the upstream region of the plaque. The fibrous cap is the starting point for rupture within the plaque, and calcification increases the stress on the fibrous cap, thereby increasing the risk of rupture.

Eulerian- lagrangian dense discrete phase model (DDPM) of stenotic LAD coronary arteries in comparison with single phase modeling

In computational fluid dynamic studies related to blood flow, investigating the behavior of blood particles is crucial, especially red blood cells as they constitute a significant proportion of blood particles. Additionally, studying red blood cell movements is necessary, especially in stenotic artery geometries. A new multiphase scheme was utilized to demonstrate the effect of red blood cells on hemodynamics in complex coronary arteries and investigate the consequence of their motion. To investigate the effect of red blood cell movement on flow, the dense discrete phase model (DDPM) was used. This simulation was performed in 3D coronary arteries with different degrees of stenosis, utilizing blood pressure as inlet and outlet boundary conditions while assuming the arterial wall to be rigid. The model prediction shows good agreement with experimental data. Velocity values were comparable in both single-phase and two-phase flow simulations, but the shear stress in two-phase modeling had higher values. In the two-phase DDPM modeling, the recirculation areas indicated a higher probability of atherosclerosis plaque re-formation in the pre-stenosis area compared to the stenosis and post-stenosis areas. The DDPM model was found to be more effective in obtaining shear stress values in the artery. Additionally, this model provides good results compared to the single-phase model in investigating the movement of particles along the artery as well as recirculation areas that lead to the deposition of particles.

Numerical investigation of quantitative pulmonary pressure ratio in different degrees of stenosis.

Pulmonary artery stenosis endangers people's health. Quantitative pulmonary pressure ratio (QPPR) is very important for clinicians to quickly diagnose diseases and develop treatment plans. Our purpose of this paper is to investigate the effects of different degrees (50% and 80%) of pulmonary artery stenosis on QPPR. An idealized model is established based on the normal size of human pulmonary artery. The hemodynamic governing equations are solved using fluid-structure interaction. The results show that the QPPR decreases with the increase of stenosis degree, and it is closely related to the pressure drop at both ends of stenosis. Blood flow velocity and wall shear stress are sensitive to the stenosis degree. When the degree of stenosis is 80%, the amplitude of changes of blood flow velocity and wall shear stress at both ends of stenosis is lower. The results suggest that the degree of pulmonary artery stenosis has a significant impact on QPPR and hemodynamic changes. This study lays a theoretical foundation for further study of QPPR.

Value evaluation of serum (sdLDLc*HCYc)/HDLc ratio in the stability of intracranial arterial plaques in patients with acute cerebral infarction.

We aimed to analyze the value of serum (sdLDLc*HCYc)/HDLc ratio in the stability of intracranial arterial plaques among patients with acute cerebral infarction. A retrospective analysis was conducted on 140 patients with acute cerebral infarction admitted to the neurology department and 101 healthy individuals for regular examinations in our hospital from 2013 to 2019, who were respectively allocated into the study group and the control group. Participants in both groups were measured for serum sdLDLc, HDLc, and HCYc using peroxidase method, enzyme-linked immunosorbent assay, and enzyme method, respectively. The laboratory indexes of the two groups were compared. The multivariate logistic regression analysis was done to analyze the influencing factors of the stability of intracranial artery plaque in patients with acute cerebral infarction. The value of high-density lipoprotein cholesterol (HDL-C), homocysteine, sdLDLc, (sdLDLc*HCYc)/HDLc in diagnosing the stability of intracranial artery plaque was also evaluated in patients with acute cerebral infarction. There was no distinct difference in height, hypertension, diabetes, coronary heart disease, smoking history and drinking history between the two groups (P>0.05). The study group showed statistically significant differences in age, gender, weight, and BMI (P<0.05). The current study demonstrated no statistical difference in the levels of TG, low-density lipoprotein cholesterol (LDL-C), α-lipoprotein, and HCYc between the two groups (P>0.05). However, the levels of TC, HDL-C, sdLDLc, (sdLDLc*HCYc)/HDLc in the study group were significantly different when comparing with the control group (P<0.05). No statistically significant difference was found in the levels of TG, triglycerides, LDL-C, α-lipoprotein, and HCYc among patients with different degrees of stenosis in the study group (P>0.05). The level of HDL-C was significantly lower in cases of severe stenosis compared to no stenosis, mild stenosis and moderate stenosis, with severe stenosis showing the lowest levels; mild stenosis had lower levels than no stenosis, while moderate stenosis had lower levels than both no stenosis and mild stenosis (P<0.05). The levels of sdLDLc, (sdLDLc*HCYc)/HDLc exhibited a significant increase in cases of severe stenosis as compared tono stenosis, mild stenosis, and moderate stenosis. Furthermore, the levels of sdLDLc, (sdLDLc*HCYc)/HDLc were found to be higher in moderate stenosis as compared to no stenosis and mild stenosis. Similarly, the levels of sdLDLc, (sdLDLc*HCYc)/HDLc were observed to be higher in mild stenosis than no stenosis (P<0.05).The independent variables were set as the indicators with difference in single factor comparison, including age, gender, BMI, TC, LDL-C, HDL-C, HCYc, sdLDLc, (sdLDLc*HCYc)/HDLc. The dependent variable was the stability of intracranial artery plaque in patients with acute cerebral infarction. After variable selection, the results showed that the factors influencing the stability of intracranial artery plaque in patients with acute cerebral infarction were age, BMI, (sdLDLc*HCYc)/HDLc. The degree of plaque enhancement was used as a criterion to reflect the stability of plaque. ROC curve analysis showed that (sdLDLc*HCYc)/HDLc had a higher evaluation value for the stability of intracranial artery plaque than HDL-C, homocysteine, and sdLDLc in patients with acute cerebral infarction. The serum (sdLDLc*HCYc)/HDLc ratio was found to have potential in evaluating the stability of intracranial arterial plaques in patients with acute cerebral infarction.

Hemodynamic analysis of unilateral and bilateral renal artery stenosis based on fluid-structure interaction

Renal artery stenosis (RAS) hypertension is a common type of secondary hypertension. This paper aimed to explore how unilateral renal artery stenosis (Uni-RAS) and bilateral renal artery stenosis (Bi-RAS) caused renovascular hypertension with the fluid-structure interaction (FSI) method. Based on a real RAS model, 20 ideal models with different stenosis degrees were established by modifying the stenosis segment. The hemodynamic parameters at different degrees of stenosis, mass flow rate (MFR), pressure drop (PD), fractional flow reserve (FFR), oscillatory shear index (OSI), and relative residence time (RRT), were numerically calculated by the computational fluid dynamics (CFD) method. The numerical results showed that RAS caused the decrease of MFR, and the increase of PD and the proportion of high OSI and high RRT. In the case of RAS, it could not be regarded as a reference indicator for causing renovascular hypertension that the value of FFR was greater than 0.9. In addition, the results of the statistical analysis indicated that Uni-RAS and Bi-RAS were statistically different for MFR, PD and the proportion of high RRT.

Diagnostic accuracy of coronary artery stenosis and thrombosis assessment using unenhanced multiplanar 3D post-mortem cardiac magnetic resonance imaging

BackgroundA 3D sequence was introduced to unenhanced post-mortem cardiac magnetic resonance imaging (PMCMR) to enable multiplanar coronary artery image analysis and to investigate its diagnostic accuracy for the diagnosis of coronary artery stenosis and thrombosis. Materials and MethodsN = 200 forensic cases with suspected coronary artery pathology underwent 3 Tesla PMCMR (sequence used: T2 weighted transversal 3D turbo spin echo) before autopsy. Main coronary artery stenosis and thrombosis were assessed in PMCMR by multiplanar image analysis by two observers. Coronary artery histology was determined as the gold standard and compared to PMCMR. Sensitivity, specificity, negative (NPV) and positive predictive values (PPV) with 95% confidence intervals were calculated. ResultsFor all coronary arteries combined, sensitivity was 75% (PPV 73%) for the diagnosis of stenosis and 72% (PPV 71%) for the diagnosis of thrombosis. Specificity was 92% (NPV 90%) for correct diagnosis of non-existing stenosis and 97% (NPV 97%) for non-existing thrombosis. Sensitivity for correct diagnosis of different degrees of stenosis ranged between 67% and 80% (PPVs 67–82%); specificity ranged between 96% and 99% (NPVs 96–99%). ConclusionMultiplanar PMCMR coronary artery stenosis and thrombosis assessment based on an unenhanced T2 weighted 3D sequence provide moderate sensitivity and high specificity for the diagnosis of coronary artery stenosis and/or thrombosis. Hence, 3D T2w PMCMR cannot reliably detect existing coronary artery stenosis and thrombosis but may be particularly useful for the exclusion of stenosis or thrombosis of the main coronary arteries.

Abstract 049: Effect of the ICA Lesion Severity in Outcomes after Endovascular Treatment of Acute Tandem LVO

Introduction Tandem Lesions (TLs) pose unique challenges in the endovascular management of acute ischemic stroke.(1) The absence of anterograde blood flow in the carotid occluded segment may limit the effectiveness of endovascular interventions, resulting in delayed reperfusion or suboptimal recanalization.(2,3) Thus, the presence of unpaired blood flow through the ICA in the context of TLs is believed to exacerbate the extension of ischemic lesions. (4,5) This study compared the clinical and procedural outcomes of patients with TLs and extracranial internal carotid artery occlusion versus those with stenosis. Methods A retrospective analysis was performed on a multicenter cohort of patients with TLs who underwent endovascular treatment. The patients were categorized into two groups: those with extracranial ICA stenosis and those with occlusion. Clinical outcomes, including functional independence, hemorrhagic events, and procedural time metrics including puncture to reperfusion time were assessed. Sensitivity analyses were conducted to evaluate these differences segregating patients according to varying degrees of stenosis, and in pre‐specified subgroups. Results A total of 513 patients with TLs were included in the study. 281 (54.8%) presented with ICA occlusion, and 232 (45.2%) presented stenosis &gt;=70% (Table 1). The comparison between the stenosis and occlusion groups revealed no significant differences in the main outcomes, including mTICI 2c‐3 (47.5% vs. 50.6%, aOR 1.07, 95% CI 0.70‐1.64, p=.751) (Figure 1), mRS 0‐2 at 90 days (43.6% vs. 48.9%, aOR 0.79, 95% CI 0.52‐1.20, p=.271), sICH rates (4.7% vs. 5.6%, aOR 0.72, 95% CI 0.31‐1.71, p=.458), and puncture to reperfusion time (58 [40‐80.5] vs. 52.5 [35.2‐80], ratio 1.04, 95% CI 0.88‐1.23, p=.64). Similar analyses performed comparing different degrees of stenosis and occlusion, and in patients treated with the antegrade approach only, did not show significant differences either. Conclusion Our findings indicate that although more severe degrees of stenosis or occlusion of the ICA prolong the time from puncture to reperfusion, no significant differences in clinical outcomes exist. The clinical implications of these findings need to be further evaluated to fully comprehend the specific needs of patients affected by TLs.

The Relation of the Iron Metabolism Index to the Vulnerability Index of Carotid Plaque with Different Degrees of Stenosis.

To investigate the differences in serum iron index and iron metabolizing protein expression in plaques in patients with different degrees of carotid artery stenosis and the relationship with plaque traits. A total of 100 patients eligible for carotid endarterectomy (CEA) from August 2021 to February 2022 were included. Patients completed a computed tomography (CTA) scan for patient grouping and a magnetic resonance imaging (MRI) for precise quantification of carotid plaque traits within 1 week prior to surgery. Clinical indicators associated with the progression of carotid stenosis to occlusion were analyzed using ordered logistic regression. Twenty carotid plaques were analyzed immunohistochemically to investigate the relationship between plaque traits and the iron metabolism indexes. No significant correlation between high serum ferritin (SF), unsaturated iron binding capacity (UIBC) and progression of carotid stenosis (OR 1.100, 95% CI 0.004-0.165, p = 0.039; OR 1.050, 95% CI 0.005-0.094, p = 0.031). SF and serum transferrin receptor (sTfR) were correlated with normalized wall index (NWI) (R = 0.470, p = 0.036; R = 0.449, p = 0.046), and the results of multiple linear regression suggested that SF and sTfR remained associated with NWI (R = 0.630, R2 = 0.397, Adjusted R2 = 0.326, p = 0.014). In plaques, H-type ferritin (H-FT) was correlated with NWI and lipid-rich necrotic core (LRNC) volume (R = 0.502, p = 0.028; R = 0.468, p = 0.043). Transferrin receptor 1 (TfR1) was correlated with LRNC volume and intraplaque hemorrhage (IPH) volume (R = 0.538, p = 0.017; R = 0.707, p = 0.001). There were statistical differences in the expression of iron metabolism proteins in carotid plaques with different degrees of stenosis. Serum iron metabolism index (SF and sTfR) and expression of iron metabolizing proteins (H-FT and TfR1) in plaques were positively correlated with carotid plaque vulnerability index (NWI, LRNC volume).

Numerical analysis of hemodynamic parameters in stenosed arteries under pulsatile flow conditions

This research studies the changes in flow patterns and hemodynamic parameters of diverse shapes and sizes of stenosis. Six different shapes and sizes of stenosis are constructed to investigate the variations in hemodynamics as the morphology changes. Changes in shape (trapezoidal and bell-shaped) and sizes of stenosis change the stresses on the walls and their flow patterns. TAWSS and OSI results specify that trapezoidal stenosis exerts greater stress than bell-shaped stenosis. Also, as the length of the trapezoidal stenosis increases, the TAWSS increases, whereas the trend is the opposite for bell-shaped stenosis. Later, this paper also studies different degrees of stenosis extracted from real images. Changes in velocity flow patterns, wall shear stress (WSS), Time-averaged wall shear stress (TAWSS) and Oscillatory shear index (OSI) have been studied for these images. Results illustrate that the peak velocity rises drastically as the stenosis percentage increases. Negative velocity is seen close to the artery's walls, indicating flow separation. This flow separation region is seen throughout the cycle except in the accelerating flow region. An increase in stenosis also increases WSS and TAWSS drastically. Negative WSS is seen downstream of stenosis, indicating flow recirculation. Such negative WSS in the blood vessels also promotes endothelial dysfunction. OSI values greater than 0.2 are seen near the stenosis region, indicating atherosclerosis growth. Regions of high OSI and low TAWSS are also identified, indicating probable regions of plaque development.

Modelling blood flow in coronary arteries: Newtonian or shear-thinning non-Newtonian rheology?

BackgroundThe combination of medical imaging and computational hemodynamics is a promising technology to diagnose/prognose coronary artery disease (CAD). However, the clinical translation of in silico hemodynamic models is still hampered by assumptions/idealizations that must be introduced in model-based strategies and that necessarily imply uncertainty. This study aims to provide a definite answer to the open question of how to properly model blood rheological properties in computational fluid dynamics (CFD) simulations of coronary hemodynamics. MethodsThe geometry of the right coronary artery (RCA) of 144 hemodynamically stable patients with different stenosis degree were reconstructed from angiography. On them, unsteady-state CFD simulations were carried out. On each reconstructed RCA two different simulation strategies were applied to account for blood rheological properties, implementing (i) a Newtonian (N) and (ii) a shear-thinning non-Newtonian (non-N) rheological model. Their impact was evaluated in terms of wall shear stress (WSS magnitude, multidirectionality, topological skeleton) and helical flow (strength, topology) profiles. Additionally, luminal surface areas (SAs) exposed to shear disturbances were identified and the co-localization of paired N and non-N SAs was quantified in terms of similarity index (SI). ResultsThe comparison between paired N vs. shear-thinning non-N simulations revealed remarkably similar profiles of WSS-based and helicity-based quantities, independent of the adopted blood rheology model and of the degree of stenosis of the vessel. Statistically, for each paired N and non-N hemodynamic quantity emerged negligible bias from Bland-Altman plots, and strong positive linear correlation (r > 0.94 for almost all the WSS-based quantities, r > 0.99 for helicity-based quantities). Moreover, a remarkable co-localization of N vs. non-N luminal SAs exposed to disturbed shear clearly emerged (SI distribution 0.95 [0.93, 0.97]). Helical flow topology resulted to be unaffected by blood rheological properties. ConclusionsThis study, performed on 288 angio-based CFD simulations on 144 RCA models presenting with different degrees of stenosis, suggests that the assumptions on blood rheology have negligible impact both on WSS and helical flow profiles associated with CAD, thus definitively answering to the question “is Newtonian assumption for blood rheology adequate in coronary hemodynamics simulations?”.

Evaluating Short-Term and Long-Term Risks Associated with Renal Artery Stenosis Position and Severity: A Hemodynamic Study.

Background: Moderate renal artery stenosis (50-70%) may lead to uncontrolled hypertension and eventually cause irreversible damage to renal function. However, the clinical criteria for interventional treatment are still ambiguous in this condition. This study investigated the impact of the position and degree of renal artery stenosis on hemodynamics near the renal artery to assess the short-term and long-term risks associated with this disease. Methods: Calculation models with different degrees of stenosis (50%, 60%, and 70%) located at different positions in the right renal artery were established based on the computed tomography angiography (CTA) of a personalized case. And computational fluid dynamics (CFD) was used to analyze hemodynamic surroundings near the renal artery. Results: As the degree of stenosis increases and the stenosis position is far away from the aorta, there is a decrease in renal perfusion. An analysis of the wall shear stress (WSS)-related parameters indicated areas near the renal artery (downstream of the stenosis and the entrance of the right renal artery) with potential long-term risks of thrombosis and inflammation. Conclusion: The position and degree of stenosis play a significant role in judging short-term risks associated with renal perfusion. Moreover, clinicians should consider not only short-term risks but also independent long-term risk factors, such as certain regions of 50% stenosis with adequate renal perfusion may necessitate prompt intervention.

Modeling of inhaled corticosteroids delivery for topical croup treatment in pediatric upper airways

Croup is the most frequent cause of pediatric upper airway obstruction characterized by spindle-shaped stenosis in the subglottis mucosa. Inhaled corticosteroids (ICSs) serve as the first-line therapy for croup. Traditional ICS particles (1–4 μm in diameter) are primarily designed for trachea and lung diseases and show extremely low larynx deposition. Moreover, the specific correlation between airway minimal cross-sectional area (CSA) and airway resistance has not been fully understood. In this study, three healthy pediatric upper airway models with commercial nebulizer masks attached to their faces were reconstructed from computed tomography (CT) scans. Virtual mild, moderate, and severe croup were incorporated into these healthy models. To enhance the performance of conventional nebulizing drug delivery, the aerodynamic properties of croup with different degrees of stenosis were quantitatively analyzed, and the respiratory transit and deposition of ICS particles sized between 1 to 20 μm in our target area (glottis + subglottis) were modeled utilizing the Computational Fluid Particle Dynamics (CFPD) method. Results showed that in all models, maximum deposition fractions (DF) can be reached when the ICS particle sizes are 7–8 μm, and for particles sized at 8 and 9 μm, all models can achieve effective target area delivery (≥75% of the maximum DF), whereas the majority of traditional nebulizers produce smaller particles than what we recommended. Pediatric upper airway resistance is negatively correlated with the minimum airspace CSA (R ∝ CSA−1), which is in good agreement with the Bernoulli Obstruction Theory. Furthermore, when the constriction of the subglottis reaches a specific level (≥70% obstruction), the upper airway pressure drop abruptly surged and the dyspneic respiration symptoms of patients develop instantly.

Numerical investigation of the effect of carotid bifurcation stenosis degree on pulsatility characteristics.

Arterial bifurcations are regions that are susceptible to hemodynamic effects and thrombus formation. In the current study, the hemodynamic effects of a simplified 3D model of an arterial bifurcation were simulated using the commercial computational fluid dynamics software FLUENT. The non-Newtonian properties of blood were modeled using the Carreau model, and the pulsation dynamics and heat transfer characteristics of blood at different degrees of stenosis in the arterial bifurcation were analyzed. The results indicate that arterial stenosis caused by a thrombus when the pulsation velocity reaches its peak has an essential impact on blood transport. The stenosis of the bifurcation increases the peak pulsatile flow pressure drop, and each 0.5mm stenosis of the arterial bifurcation increases the mean wall shear stress of the bifurcated segment by approximately 0.25Pa. From the heat transfer perspective, arterial stenosis has little effect on the heat transfer coefficient. The heat transfer coefficient measured inside the bifurcation is much larger than that measured outside the bifurcation. The stenosis of the arterial bifurcation causes an increase in the mean velocity of the arterial cross-section, and the volume-averaged absolute vorticity is introduced to quantify the secondary flow effect during the pulsation cycle, where the arterial stenosis causes an increase in the mean absolute vorticity at pulsation velocity and accelerates the decay of the vorticity at uniform velocity. In this paper, the hemodynamics of carotid bifurcation pulsation is analyzed in conjunction with flow field properties to reveal the flow field dynamics factors and heat transfer characteristics of local stenosis of the carotid bifurcation and to conduct an exploratory study for the diagnosis and treatment of carotid bifurcation thrombosis.

Association between CZT‑SPECT myocardial blood flow and coronary stenosis: A cross‑sectional study.

The association between the quantitative and semi-quantitative parameters of myocardial blood flow obtained using cadmium-zinc-telluride single photon emission computed tomography (CZT-SPECT) and coronary stenosis remains unclear. Therefore, the objective of the present study was to evaluate the diagnostic value of two parameters obtained using CZT-SPECT in patients with suspected or known coronary artery disease. A total of 24 consecutive patients who underwent CZT-SPECT and coronary angiography within 3 months of each other were included in the study. To evaluate the predictive ability of the regional difference score (DS), coronary flow reserve (CFR), and the combination thereof for positive coronary stenosis at the vascular level, receiver operating characteristic (ROC) curves were plotted and the area under the curves (AUCs) were calculated. Comparisons of the reclassification ability for coronary stenosis between different parameters were assessed by calculating the net reclassification index (NRI) and the integrated discrimination improvement (IDI). The 24 participants (median age: 65 years; range: 46-79 years; 79.2% male) included in this study had a total of 72 major coronary arteries. When stenosis ≥50% was defined as the criteria for positive coronary stenosis, the AUCs and the 95% confidence interval (CI) for regional DS, CFR, and the combination of the two indices were 0.653 (CI, 0.541-0.766), 0.731 (CI, 0.610-0.852) and 0.757 (CI, 0.645-0.869), respectively. Compared with single DS, the combination of DS and CFR increased the predictive ability for positive stenosis, with an NRI of 0.197-1.060 (P<0.01) and an IDI of 0.0150-0.1391 (P<0.05). When stenosis ≥75% was considered as the criteria, the AUCs were 0.760 (CI, 0.614-0.906), 0.703 (CI, 0.550-0.855), and 0.811 (CI, 0.676-0.947), respectively. Compared with DS, CFR had an IDI of -0.3392 to -02860 (P<0.05) and the combination of DS and CFR also enhanced the predictive ability, with an NRI of 0.0313-1.0758 (P<0.01). In conclusion, both regional DS and CFR had diagnostic values for coronary stenosis, but the diagnostic abilities differed in distinguishing between different degrees of stenosis, and the efficiency was improved with a combination of DS and CFR.

Internal carotid artery stenosis: hemodynamics in the ipsilateral ACA affects CT angiography manifestations.

This study aimed to evaluate whether CT angiography (CTA) manifestations in anterior cerebral artery a1 segment (A1) were related to the hemodynamics in patients with internal carotid artery stenosis (ICAS). A total of 97 cases were selected. The degree of ICAS and symmetry of A1 were evaluated by CTA examination. Hemodynamic indexes were detected by transcranial Doppler (TCD). The differences in CTA presentations of A1 and hemodynamics between the vessels on the stenotic and contralateral sides were analyzed according to the different degrees of stenosis. The degree of ICAS according to the different manifestations of A1 and the hemodynamics of A1's adjacent vessels were also analyzed. In the case of unilateral ICAS, the difference in Vm of A1 between the stenotic and the contralateral side was the most significant relative to the stenosis degree. When unilateral ICAS was ≥70%, the presentation of A1 on the stenotic side was more slender or non-visualized compared to that on the contralateral side, while in cases with unilateral stenosis <70% or bilateral stenosis with a similar degree of stenosis, A1 were mainly symmetrical. When A1 on the side of ICAS was slender or non-visualized, the Vm of A1 was significantly slower than that on the contralateral side (P < 0.001). The CTA manifestations of A1 on the side of ICAS embodied the overall changes of the intracranial hemodynamics after ICAS. A combination of TCD and CTA examination of A1 can assist in judging the location and degree of ICAS.

Patient-specific computational simulation of coronary artery bypass grafting.

Coronary artery bypass graft surgery (CABG) is an intervention in patients with extensive obstructive coronary artery disease diagnosed with invasive coronary angiography. Here we present and test a novel application of non-invasive computational assessment of coronary hemodynamics before and after bypass grafting. We tested the computational CABG platform in n = 2 post-CABG patients. The computationally calculated fractional flow reserve showed high agreement with the angiography-based fractional flow reserve. Furthermore, we performed multiscale computational fluid dynamics simulations of pre- and post-CABG under simulated resting and hyperemic conditions in n = 2 patient-specific anatomies 3D reconstructed from coronary computed tomography angiography. We computationally created different degrees of stenosis in the left anterior descending artery, and we showed that increasing severity of native artery stenosis resulted in augmented flow through the graft and improvement of resting and hyperemic flow in the distal part of the grafted native artery. We presented a comprehensive patient-specific computational platform that can simulate the hemodynamic conditions before and after CABG and faithfully reproduce the hemodynamic effects of bypass grafting on the native coronary artery flow. Further clinical studies are warranted to validate this preliminary data.

Elevated Lp(a) Levels Correlate with Severe and Multiple Coronary Artery Stenotic Lesions.

The role of Lipoprotein(a) (Lp(a)) in increasing the risk of cardiovascular diseases is reported in several populations. The aim of this study is to investigate the correlation of high Lp(a) levels with the degree of coronary artery stenosis. Two hundred and sixty-eight patients were enrolled for this study. Patients who underwent coronary artery angiography and who had Lp(a) measurements available were included in this study. Binomial logistic regressions were applied to investigate the association between Lp(a) and stenosis in the four major coronary arteries. The effect of LDL and HDL Cholesterol on modulating the association of Lp(a) with coronary artery disease (CAD) was also evaluated. Multinomial regression analysis was applied to assess the association of Lp(a) with the different degrees of stenosis in the four major coronary arteries. Our analyses showed that Lp(a) is a risk factor for CAD and this risk is significantly apparent in patients with HDL-cholesterol ≥35 mg/dL and in non-obese patients. A large proportion of the study patients with elevated Lp(a) levels had CAD even when exhibiting high HDL serum levels. Increased HDL with low Lp(a) serum levels were the least correlated with stenosis. A significantly higher levels of Lp(a) were found in patients with >50% stenosis in at least two major coronary vessels arguing for pronounced and multiple stenotic lesions. Finally, the derived variant (rs1084651) of the LPA gene was significantly associated with CAD. Our study highlights the importance of Lp(a) levels as an independent biological marker of severe and multiple coronary artery stenosis.

Simulating Stenotic Conditions of the Coronary Artery in a Lumped Parameter Model of the Cardiovascular System.

Coronary flow control mechanisms maintain the average coronary blood flow (CBF) at 4% of the cardiac output (CO) in normal adults, with no prior diagnosis of coronary artery disease (CAD), under resting conditions. This paper explores a pulsatile sixth order lumped parameter (LP) model of the cardiovascular system (CVS) which utilizes the average CBF approximated from CO along with arterial blood pressure (ABP) waveform to estimate the coronary microvascular resistance using non-linear least square optimization technique. The CVS model includes a third order model of the coronary vascular bed and is shown to achieve phasic coronary flow. The coronary epicardial resistance is varied to emulate different degrees of stenosis and achieve realistic behavior of coronary microvascular resistance under these conditions.

The value of whole-brain CT perfusion imaging combined with dynamic CT angiography in the evaluation of pial collateral circulation with middle cerebral artery occlusion.

Middle cerebral artery (MCA) occlusion is extremely common, especially unilateral artery, which can result in a significant incidence of cerebral infarction. To assess the value of whole-brain computed tomography perfusion (CTP) imaging combined with dynamic CT angiography (dCTA) in the evaluation of pial collateral circulation in patients with MCA occlusion. Whole-brain CTP and dCTA images were acquired in 58 patients with unilateral MCA occlusion. All patients were divided into three groups according to the American Society of Interventional and Therapeutic Neuroradiology/Society of Interventional Radiology (ASITN/SIR) collateral score (by CTA). The CTP parameters were analysed, including relative cerebral blood flow (rCBF), relative cerebral blood volume (rCBV), relative mean transit time (rMTT), and relative time to peak (rTTP). Patients were followed up with the modified Rankin scale (mRS). All cases in this study were confirmed by DSA. The CTP parameters of the MCA blood supply area on the affected side of patients with different degrees of stenosis were significantly different from those on the unaffected side. There are significant differences in the CTP parameters and openings of the Willis circle in patients with different degrees of stenosis. Significant differences were found in the number of patients with good prognosis. Whole-brain CT perfusion combined with dynamic CTA can structurally and functionally evaluate the establishment of pial collateral circulation and its effect on cerebral hemodynamic changes.

Whole-Brain Volume CT Angiography can Effectively Detect Early Ischemic Cerebrovascular Diseases.

To investigate the role of whole-brain volume computed tomography (CT) perfusion in assessing early ischemic cerebrovascular diseases. Seventy-two patients with early ischemic cerebrovascular diseases who had undergone routine CT scan and 320-row volume CT whole-brain perfusion imaging within 8 h after admission were retrospectively enrolled in this one-center case-sectional study. The perfusion parameters of cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), time to peak (TTP), and dynamic CT angiogram (4D-CTA) were obtained and analyzed. Among 72 patients, 29 cases with 37 cerebral ischemic lesions were found in plain CT scan, whereas 51 cases with 76 lesions were found in whole-brain CT perfusion, with 30.6% more patients being detected. The CBF value was significantly lower in the abnormal than normal corresponding perfusion area in the healthy hemisphere (P<0.05), while the MTT and TTP values were significantly higher in the abnormal than the normal corresponding area (P<0.05). 4D-CTA image suggested that 59 cases had different degrees of stenosis or occlusion, including 11 mild, 18 moderate, 21 severe, and 9 occlusive cases. Four-D-CTA imaging could detect significantly (P<0.05) more patients with abnormal perfusion in severe cerebral vascular stenosis or occlusion than those with no, mild or moderate stenosis (93.33% vs. 16.67%) (P<0.05). The stenosis of intracranial and carotid arteries was positively correlated with MTT and TTP values (P<0.05). Whole-brain volume CT angiography can comprehensively display early cerebral ischemic lesions, cerebral blood perfusion status, and cerebral vascular stenosis, providing valuable information for early detection of ischemic cerebral diseases and appropriate treatment planning.