Risk stratification in symptomatic intracranial atherosclerotic disease with conventional vascular risk factors and cerebral haemodynamics

Retearing of type B blind cystic aortic dissection: computational fluid dynamics analysis

Aortic dissection (AD) is a serious life-threatening vascular disease. However, research on type B blind cystic AD is still insufficient. This type of AD involves only one proximal intimal tear, and the distal end of the aortic false lumen (FL) is a blind sac. The purpose of this study was to explore the haemodynamic indicators of retearing and high-risk areas for FL rupture in type B blind cystic AD patients. This study included 4 cases of type B blind cystic AD rupture death, which revealed the pathological characteristics of the aorta. In addition, imaging data from one deceased and four patients with type B AD (TBAD) with multiple intimal tears were collected, and two groups of models (n = 10) were constructed. The pressure, velocity, time-averaged wall shear stress (TAWSS), and relative residence time (RRT) were compared to interpret our autopsy results. In type B blind cystic AD patients, the FL is characterized by high pressure, a low TAWSS, and high RRT. There was a relatively high TAWSS in the FL adjacent to the proximal intimal tear; at the same time, both the blood flow velocity and the pressure difference in the true lumen (TL) significantly changed. In addition, the greater the curvature of the aorta is, the more drastic the change in the luminal pressure difference. In type B blind cystic AD, high pressure may be the main reason for FL rupture, and the FL adjacent to the proximal intimal tear may be a high-risk rupture area. In addition, alterations in blood flow velocity and differential pressure may cause distal intimal retears. Tortuosity is an important indicator for studying pressure changes.

Anatomical location-related hemodynamic variations are associated with atherosclerosis in the middle cerebral artery: a preliminary cross-sectional 4D flow and 3D vessel wall MRI study

Background

Hemodynamics is crucial for the assessment of atherosclerotic development. However, flow alterations due to plaque existence and increased plaque number in different intracranial arterial segments have not been fully understood. This study aimed to investigate the relationship of wall shear stress (WSS) parameters between middle cerebral arteries (MCAs) with and without plaque and explore the potential discrepancy between multiple- and single-plaque existence.

Methods

Consecutive patients with MCA atherosclerosis were recruited and underwent four-dimensional (4D) flow magnetic resonance imaging (MRI) and three-dimensional (3D) vessel wall imaging (VWI). Time-averaged WSS (TAWSS), time-averaged WSS coefficient variation (TAWSSCV), and oscillatory shear index (OSI) were measured at five cross-sectional slices [initial, upstream, the most narrowed lumen (MNL), downstream, and terminal] of plaque and reference (REF) sites to describe lesion-level hemodynamics. Segment-level hemodynamics of M1 and M2 segments were also analyzed. MCA geometry and plaque characteristics were calculated. The MCAs were then classified into four groups according to plaque presence in different segments: Group I, without plaque; Group II, with plaque only in M1; Group III, with plaque in both M1 and M2; Group IV, with plaque only in M2. The above parameters were compared in MCA with and without plaque as well as single- and multiple-plaque (≥2) MCAs.

Results

A total of 150 MCAs with 231 plaques from 79 patients were investigated. TAWSSmin showed a relatively larger value at the proximal portion compared to the distal portion across plaque in both M1 and M2 segments. Lower lesion-level TAWSSmin was found in the M1 plaque presence of Group III compared to Group I and Group II (P=0.026 and P=0.014). Similar association was also observed in the M2 plaque presence of Groups III and IV compared to Group I (P=0.010 and P=0.008), whereas lower segment-level TAWSSmin was only seen in the M2 segment of Group III compared to Group I (P=0.039). Lower OSImean was found both in the M1 presence of Group II and III compared to Group I (P=0.013 and P=0.048) and OSImax was found in the M1 plaque presence of Group II compared to Group I (P=0.036). Lower stenosis was found in single-plaque compared to multiple-plaque groups (P=0.045 and P=0.049). Lower lesion-level highest/initial TAWSSmean ratio (P=0.037) and highest/initial TAWSSmax ratio (P=0.013) were found in the single-plaque M1 group compared to the multiple-plaque M1 group. The M1 geometry and positive remodeling (PR) were different between single- and multiple-plaque M1 groups whereas maximum wall thickness (maxWT) and normalized wall index (NWI) showed differences between the single- and multiple-plaque M2 groups (all P<0.05).

Conclusions

Hemodynamic alterations are observed under the impacts of atherosclerosis and are different between M1 plaque and M2 plaque. Single- and multiple-plaque MCAs exhibit different geometry, plaque characteristics, and hemodynamics, and these vary according to segments. The interplay of arterial segment, plaque number, and characteristics as well as hemodynamics could provide insight for the mechanisms of atherosclerotic existence.

Clinical implications of haemodynamics in symptomatic intracranial atherosclerotic stenosis by computational fluid dynamics modelling: a systematic review

BACKGROUND

Recently, computational fluid dynamics (CFD) has been used to simulate blood flow of symptomatic intracranial atherosclerotic stenosis (sICAS) and investigate the clinical implications of its haemodynamic features, which were systematically reviewed in this study.

METHODS

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses and Meta-analysis of Observational Studies in Epidemiology statements, we searched PubMed and Embase up to March 2024 and screened for articles reporting clinical implications of haemodynamic parameters in sICAS derived from CFD models.

RESULTS

19 articles met the inclusion criteria, all studies recruiting patients from China. Most studies used CT angiography (CTA) as the source image for vessel segmentation, and generic boundary conditions, rigid vessel wall and Newtonian fluid assumptions for CFD modelling, in patients with 50%-99% sICAS. Pressure and wall shear stress (WSS) were quantified in almost all studies, and the translesional changes in pressure and WSS were usually quantified with a poststenotic to prestenotic pressure ratio (PR) and stenotic-throat to prestenotic WSS ratio (WSSR). Lower PR was associated with more severe stenosis, better leptomeningeal collaterals, prolonged perfusion time and internal borderzone infarcts. Higher WSSR and other WSS measures were associated with positive vessel wall remodelling, regression of luminal stenosis and artery-to-artery embolism. Lower PR and higher WSSR were both associated with the presence and severity of cerebral small vessel disease. Moreover, translesional PR and WSSR were promising predictors for stroke recurrence in medically treated patients with sICAS and outcomes after acute reperfusion therapy, which also provided indicators to assess the effects of stenting treatment on focal haemodynamics.

CONCLUSIONS

CFD is a promising tool in investigating the pathophysiology of ICAS and in risk stratification of patients with sICAS. Future studies are warranted for standardisation of the modelling methods and validation of the simulation results in sICAS, for its wider applications in clinical research and practice.

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.

Intravascular enhancement sign at 3D T1-weighted turbo spin echo sequence is associated with cerebral atherosclerotic stenosis

OBJECTIVE

Intravascular enhancement sign (IVES) at three-dimensional T1-weighted turbo spin echo (3D T1W TSE) sequence may be a simple hemodynamic maker. This study aims to investigate the association between IVES and features of intracranial atherosclerotic stenosis (ICAS).

METHOD

Retrospective analysis of clinical and imaging data of patients who underwent high resolution-vessel wall imaging (HR-VWI) examination from May 2021 to May 2023. The number of IVES vessels and ICAS features at HR-VWI were extracted by two neuroradiologists. Paired comparisons and correlation analysis on these indicators were performed.

RESULTS

A total of 118 patients with ICAS in the first segment of the middle cerebral artery and accompanied by unilateral IVES were enrolled. Compared to the non-IVES side, a higher incidence of ischemic events and intraplaque hemorrhage (IPH), higher degree of vascular stenosis and enhancement, lower remodeling index, and lower signal intensity ratio (SIR) were found in subjects with IVES. In the ICAS with IVES, 79.66 % showed severe stenosis and occlusion; in the ICAS with severe stenosis and occlusion, 89.5 % showed IVES in the distal. A multivariable logistic regression model identified the vascular stenosis degree (OR = 1.922; 95 %CI [1.37-2.692]; P < 0.001), enhanced-degree (OR = 2.486; 95 %CI [1.315-4.698]; P = 0.005), position (OR = 2.869; 95 %CI [1.255-6.560]; P = 0.012), and SIR (OR = 0.032; 95 %CI [0.004-0.275]; P = 0.002) were independent association with the presence of IVES. The area under the curve was 0.911 for the use of IVES vessel quantities to identify severe stenosis and occlusion of arterial lumen.

CONCLUSION

The number of IVES vessels was associated with the local features of ICAS, which may indicate severe stenosis and occlusion in the major branches of the proximal artery.

Angiography‑based quantitative flow ratio for functional assessment of intracranial atherosclerotic disease

BACKGROUND

Intracranial atherosclerotic stenosis (ICAS), an important cause of stroke, is associated with a considerable stroke recurrence rate despite optimal medical treatment. Further assessment of the functional significance of ICAS is urgently needed to enable individualised treatment and, thus, improve patient outcomes.

AIMS

We aimed to evaluate the haemodynamic significance of ICAS using the quantitative flow ratio (QFR) technique and to develop a risk stratification model for ICAS patients.

METHODS

Patients with moderate to severe stenosis of the middle cerebral artery, as shown on angiography, were retrospectively enrolled. For haemodynamic assessment, the Murray law-based QFR (μQFR) was performed on eligible patients. Multivariate logistic regression models composed of μQFR and other risk factors were developed and compared for the identification of symptomatic lesions. Based on the superior model, a nomogram was established and validated by calibration.

RESULTS

Among 412 eligible patients, symptomatic lesions were found in 313 (76.0%) patients. The μQFR outperformed the degree of stenosis in discriminating culprit lesions (area under the curve [AUC]: 0.726 vs 0.631; DeLong test p-value=0.001), and the model incorporating μQFR and conventional risk factors also performed better than that containing conventional risk factors only (AUC: 0.850 vs 0.827; DeLong test p-value=0.034; continuous net reclassification index=0.620, integrated discrimination improvement=0.057; both p<0.001). The final nomogram showed good calibration (p for Hosmer-Lemeshow test=0.102) and discrimination (C-statistic 0.850, 95% confidence interval: 0.812-0.883).

CONCLUSIONS

The μQFR was significantly associated with symptomatic ICAS and outperformed the angiographic stenosis severity. The final nomogram effectively discriminated symptomatic lesions and may provide a useful tool for risk stratification in ICAS patients.

Machine Learning for Onset Prediction of Patients with Intracerebral Hemorrhage

Objective: Intracerebral hemorrhage (ICH) has a high mortality and long-term morbidity and thus has a significant overall health–economic impact. Outcomes are especially poor if the exact onset is unknown, but reliable imaging-based methods for onset estimation have not been established. We hypothesized that onset prediction of patients with ICH using artificial intelligence (AI) may be more accurate than human readers. Material and Methods: A total of 7421 computed tomography (CT) datasets between January 2007–July 2021 from the University Hospital Basel with confirmed ICH were extracted and an ICH-segmentation algorithm as well as two classifiers (one with radiomics, one with convolutional neural networks) for onset estimation were trained. The classifiers were trained based on the gold standard of 644 datasets with a known onset of >1 and <48 h. The results of the classifiers were compared to the ratings of two radiologists. Results: Both the AI-based classifiers and the radiologists had poor discrimination of the known onsets, with a mean absolute error (MAE) of 9.77 h (95% CI (confidence interval) = 8.52–11.03) for the convolutional neural network (CNN), 9.96 h (8.68–11.32) for the radiomics model, 13.38 h (11.21–15.74) for rater 1 and 11.21 h (9.61–12.90) for rater 2, respectively. The results of the CNN and radiomics model were both not significantly different to the mean of the known onsets (p = 0.705 and p = 0.423). Conclusions: In our study, the discriminatory power of AI-based classifiers and human readers for onset estimation of patients with ICH was poor. This indicates that accurate AI-based onset estimation of patients with ICH based only on CT-data may be unlikely to change clinical decision making in the near future. Perhaps multimodal AI-based approaches could improve ICH onset prediction and should be considered in future studies.

Artificial Intelligence in Hypertension Management: An Ace up Your Sleeve

Arterial hypertension (AH) is a progressive issue that grows in importance with the increased average age of the world population. The potential role of artificial intelligence (AI) in its prevention and treatment is firmly recognized. Indeed, AI application allows personalized medicine and tailored treatment for each patient. Specifically, this article reviews the benefits of AI in AH management, pointing out diagnostic and therapeutic improvements without ignoring the limitations of this innovative scientific approach. Consequently, we conducted a detailed search on AI applications in AH: the articles (quantitative and qualitative) reviewed in this paper were obtained by searching journal databases such as PubMed and subject-specific professional websites, including Google Scholar. The search terms included artificial intelligence, artificial neural network, deep learning, machine learning, big data, arterial hypertension, blood pressure, blood pressure measurement, cardiovascular disease, and personalized medicine. Specifically, AI-based systems could help continuously monitor BP using wearable technologies; in particular, BP can be estimated from a photoplethysmograph (PPG) signal obtained from a smartphone or a smartwatch using DL. Furthermore, thanks to ML algorithms, it is possible to identify new hypertension genes for the early diagnosis of AH and the prevention of complications. Moreover, integrating AI with omics-based technologies will lead to the definition of the trajectory of the hypertensive patient and the use of the most appropriate drug. However, AI is not free from technical issues and biases, such as over/underfitting, the "black-box" nature of many ML algorithms, and patient data privacy. In conclusion, AI-based systems will change clinical practice for AH by identifying patient trajectories for new, personalized care plans and predicting patients' risks and necessary therapy adjustments due to changes in disease progression and/or therapy response.

Comparison of thrombosis risk in an abdominal aortic dissection aneurysm with a double false lumen using computational fluid dynamic simulation method

BACKGROUND: Aneurysms are associated with a mortality rate of 81% or more in cases of rupture. OBJECTIVE: To analyse the haemodynamic indices and compare the thrombosis risk in a double false lumen abdominal aortic dissection aneurysm using computational fluid dynamics (CFD). METHODS: Computer tomography angiography (CTA) imaging data were collected from a patient with a double false lumen abdominal aortic dissection aneurysm, and three different lesion morphology aneurysm models were established, double false lumen abdominal aortic dissection aneurysm, single false lumen abdominal aortic dissection aneurysm and saccular abdominal aortic aneurysm, in order to analyse the flow velocity, time-averaged shear stress (TAWSS), oscillatory shear index (OSI), relative residence time (RRT) of blood flow, and endothelial cell activation potential (ECAP). RESULTS: All three aneurysms were in a low-flow state within the body, and the low-flow velocity flow in the proximal vessel wall extended to the right common iliac artery; the vortex intensity was more intense in the abdominal aortic dissection aneurysm than in the saccular abdominal aortic aneurysm. The risk area for thrombosis was concentrated in the expansion part of the aneurysm and the false lumen. The RRT and ECAP maxima of the double false lumen abdominal aortic dissection aneurysm were much greater than those of the single false lumen dissection aneurysm and saccular aortic aneurysm. CONCLUSION: Low-velocity blood flow, high OSI, low TAWSS, high RRT, and high ECAP regions correlate with the risk of thrombosis. The double false lumen type of abdominal aortic dissection aneurysm had some specificity in this case. The risk of thrombosis in the patient was extremely high, and the largest risk zone was within the smaller false lumen, which could be because the smaller false lumen was connected to the true lumen by only one breach. The results of the study provide some guidance in the early screening and development of treatment plans.

Elevated stress hyperglycemia and the presence of intracranial artery stenosis increase the risk of recurrent stroke

BACKGROUND

Stress hyperglycemia has served as a reliable biomarker to predict poor outcomes after ischemic stroke. However, recent studies have reported some contrary conclusions. Different stroke subtypes may respond inconsistently to stress hyperglycemia. The progression of intracranial atherosclerotic stenosis (ICAS) is tightly related to hyperglycemia. Thus, this study aims to determine the relationship between stress hyperglycemia and recurrent stroke in ischemic stroke patients with or without intracranial atherosclerotic stenosis.

METHODS

This is a multicenter retrospective observational cohort study. Patients with acute minor ischemic stroke and eligible computed tomography and magnetic resonance imaging data were enrolled. The severity of stress hyperglycemia is measured by the stress hyperglycemia ratio (SHR). SHR was calculated based on fasting plasma glucose (FPG) and hemoglobin A1c (HbA1c) levels. The primary outcome was stroke recurrence during hospitalization. The interaction of SHR levels with the presence of ICAS on the primary outcome was investigated using univariable and multivariable Cox proportional hazards models. Restricted cubic splines were applied to determine the nonlinear relationship between SHR and primary outcome. A two-piecewise linear regression model was used to identify the threshold of SHR.

RESULTS

A total of 610 participants were included in the study. The average age of the patients was 61.4 ± 12.9 years old, and approximately 70% of participants were males. A total of 189 (30.98%) patients had ICAS. The patients were categorized into 3 groups based on the tertiles of SHR. Compared with the group with a lower SHR, a higher SHR was significantly associated with the risk of stroke recurrence in the ICAS group (hazard ratio [HR], 8.52, 95% confidence interval [CI], 3.16-22.96, P<0.001). When SHR was treated as a continuous variable, each 0.1-unit increase in SHR in the ICAS group was associated with a 1.63-fold increase in the risk of recurrence (HR, 1.63, 95% CI, 1.39-1.9, P<0.001) with a threshold of 0.75. FPG but not HbA1c was associated with stroke recurrence in ICAS patients (HR, 1.17, 95% CI, 1.08-1.26, P<0.001). Sensitive analyses showed consistent results after adjusting for previous diabetes mellitus, oral hypoglycemic agents and insulin injection.

CONCLUSIONS

SHR represents a better biomarker to predict the risk of stroke recurrence in patients with ICAS than FPG and HbA1c regardless of previous diabetes mellitus.

TRIAL REGISTRATION

https://www.chictr.org.cn/showproj.aspx?proj=125817; Identifier, [ChiCTR2100046958].