Vessel Tortuosity Research Articles

Intravascular lithotripsy-assisted transfemoral transcatheter aortic valve implantation after failed balloon angioplasty in patients with severe calcified peripheral artery disease.

Calcific peripheral artery disease (PAD) is a common finding in patients scheduled for transcatheter aortic valve implantation (TAVI) and often requires iliofemoral axis preparation. However, evidence about the use of intravascular lithotripsy (IVL) in this setting is scarce. The aim of this study was to describe in-hospital and mid-term outcomes of IVL-assisted transfemoral (TF)-TAVI in patients with severe calcific PAD. The study included 13 patients with severe calcified PAD who were initially scheduled for balloon angioplasty (PTA)-assisted TF-TAVI but were eventually treated with peripheral IVL between October 2020 and February 2024. Accurate analysis of preoperative computed tomography scans revealed difficult TF access routes (severe calcified PAD with minimal lumen diameter ≤ 4.5 mm, circumferential calcification along iliofemoral axis, and marked vessels tortuosity). In all cases, IVL was performed after PTA failure and allowed successful valve delivery. One patient had procedural bleeding (BARC-3a). The valve was successfully delivered without complications in 12 patients (92.3%), and no major adverse events were reported at the longest follow-up (median 18.5 months). IVL-assisted TF-TAVI may represent a feasible and safe option for patients presenting with severe aortic stenosis and severe calcified PAD. However, standardization of the access site severity as well as indications for a planned up-front IVL-assisted strategy are missing and require dedicated studies.

Hemodynamic Characteristics of a Tortuous Microvessel Using High-Fidelity Red Blood Cell Resolved Simulations.

Tortuous microvessels are characteristic of microvascular remodeling associated with numerous physiological and pathological scenarios. Three-dimensional (3D) hemodynamics in tortuous microvessels influenced by red blood cells (RBCs), however, are largely unknown, and important questions remain. Is blood viscosity influenced by vessel tortuosity? How do RBC dynamics affect wall shear stress (WSS) patterns and the near-wall cell-free layer (CFL) over a range of conditions? The objective of this work was to parameterize hemodynamic characteristics unique to a tortuous microvessel. RBC-resolved simulations were performed using an immersed boundary method-based 3D fluid dynamics solver. A representative tortuous microvessel was selected from a stimulated angiogenic network obtained from imaging of the rat mesentery and digitally reconstructed for the simulations. The representative microvessel was a venule with a diameter of approximately 20 μm. The model assumes a constant diameter along the vessel length and does not consider variations due to endothelial cell shapes or the endothelial surface layer. Microvessel tortuosity was observed to increase blood apparent viscosity compared to a straight tube by up to 26%. WSS spatial variations in high curvature regions reached 23.6 dyne/cm2 over the vessel cross-section. The magnitudes of WSS and CFL thickness variations due to tortuosity were strongly influenced by shear rate and negligibly influenced by tube hematocrit levels. New findings from this work reveal unique tortuosity-dependent hemodynamic characteristics over a range of conditions. The results provide new thought-provoking information to better understand the contribution of tortuous vessels in physiological and pathological processes and help improve reduced-order models.

Association between cervicocerebral artery dissection and tortuosity - a review on quantitative and qualitative assessment.

Cervicocerebral artery dissection stands out as a significant contributor to ischemic stroke in young adults. Several studies have shown that arterial tortuosity is associated with dissection. We searched Pubmed and Embase to identify studies on the association between arterial tortuosity and cervicocerebral artery dissection, and to perform a review on the epidemiology of cervicocerebral artery tortuosity and dissection, pathophysiology, measurement of vessels tortuosity, strength of association between tortuosity and dissection, clinical manifestation and management strategies. The prevalence of tortuosity in dissected cervical arteries was reported to be around 22%-65% while it is only around 8%-22% in non-dissected arteries. In tortuous cervical arteries elastin and tunica media degradation, increased wall stiffness, changes in hemodynamics as well as arterial wall inflammation might be associated with dissection. Arterial tortuosity index and vertebrobasilar artery deviation is used to measure the level of vessel tortuosity. Studies have shown an independent association between these two measurements and cervicocerebral artery dissection. Different anatomical variants of tortuosity such as loops, coils and kinks may have a different level of association with cervicocerebral artery dissection. Symptomatic patients with extracranial cervical artery dissection are often treated with anticoagulant or antiplatelet agents, while patients with intracranial arterial dissection were often treated with antiplatelets only due to concerns of developing subarachnoid hemorrhage. Patients with recurrent ischemia, compromised cerebral blood flow or contraindications for antithrombotic agents are usually treated with open surgery or endovascular technique. Those with subarachnoid hemorrhage and intracranial artery dissection are often managed with surgical intervention due to high risk of re-hemorrhage.

Longitudinal associations of retinal vessel morphology with intraocular pressure and blood pressure at follow-up visit-Findings from a Danish eye and vision cohort, Project FOREVER.

To characterise the retinal vasculometry of a Danish eye and vision cohort and examine associations with systolic blood pressure (BP), diastolic BP, mean arterial BP, and intraocular pressure (IOP). Longitudinal study. The retinal vasculature of fundus images from the FOREVER (Finding Ophthalmic Risks and Evaluating the Value of Eye exams and their predictive Reliability) cohort was analysed using a fully automated image analysis program. Longitudinal associations of retinal vessel morphology at follow-up visit with IOP (baseline and follow-up) and BP (follow-up) were examined using multilevel linear regression models adjusting for age, sex and retinal vasculometry at baseline as fixed effects and person as random effect. Width measurements were additionally adjusted for the spherical equivalent. A total of 2089 subjects (62% female) with a mean age of 61 (standard deviation 8) years and a mean follow-up period of 4.1 years (SD 0.6 years) were included. The mean arteriolar diameter was approximately 20% thinner than the mean venular diameter, and venules were about 21%-23% less tortuous than arterioles. BP at follow-up was associated with decreased arteriolar diameter from baseline to follow-up. After adjusting for baseline IOP, IOP at follow-up was associated with increased arteriolar tortuosity above baseline (0.59%, 95% CI 0.08-1.10, p-value 0.024). In a Danish eye and vision cohort, variations in BP and alterations in IOP over time were associated with changes in the width and tortuosity of retinal vessels. Our findings contribute novel insights into retinal vascular alterations over time.

First-Line Aspiration Thrombectomy of M2 Occlusions with a Novel Reperfusion Catheter (REDTM 62): Real-World Experience from Two Tertiary Comprehensive Stroke Centers.

The direct aspiration first pass technique (ADAPT) is an effective and safe endovascular treatment for distal medium vessel occlusions (DMVOs). We evaluated technical features and initial results of a novel reperfusion catheter (REDTM 62) used for frontline aspiration thrombectomy of M2 occlusions in acute ischemic stroke patients. Appropriate aspiration catheters are crucial for a successful ADAPT maneuver; however, the selection of catheters suitable for smaller-sized vessels is scarce compared to the ones for large vessel occlusions. All patients treated with ADAPT using REDTM 62 as the frontline treatment approach for acute M2 occlusions between December 2022 and February 2024 were retrospectively enrolled. Demographic data, procedural timings and safety, recanalization rates, and outcome data were recorded. Twenty patients with a median admission National Institutes of Health Stroke Scale (NIHSS) score of 8 were identified. Successful revascularization (DMVO-thrombolysis in cerebral infarction [TICI]≥2b) with REDTM 62 aspiration thrombectomy was obtained in 65.0% (13/20) of cases. The first pass effect was 45.0% (9/20). In 2 cases, the REDTM 62 did not reach the clot due to marked distal vessel tortuosity. Stent retrievers were additionally used in 9 cases and led to an overall DMVO-TICI 2c/3 of 90.0% (18/20). Mean procedural time was 48 minutes. No complications directly related to ADAPT occurred. In-hospital mortality rate was 20.0% (4/20). The median discharge NIHSS score was 2.5. A good functional outcome at discharge (modified Rankin scale 0-2) was achieved in 55.0% (11/20) of cases. Our initial experiences with the novel REDTM 62 reperfusion catheter for treatment of M2 occlusions is in line with published data. ADAPT using this catheter may be considered as a safe and effective first-line treatment option. Further studies are warranted to validate the initial results.

Retinal microvascular remodeling associates with adverse events in continuous-flow left ventricular assist device-supported patients

BackgroundContinuous-flow left ventricular assist device (cfLVAD) use is effective in supporting patients with end-stage heart failure (ESHF). Reduced flow pulsatility within the systemic circulation in cfLVAD-supported patients may lead to alterations within the microcirculation. Temporal changes in microvasculature in relation to adverse events in cfLVAD supported patients has not been studied. We aimed to profile changes within retinal microvasculature and its association with adverse events. MethodsRetinal photography was performed using Topcon TRC-NW8 non-mydriatic fundus camera in cfLVAD supported patients and ESHF control patients. Retinal measurements including arteriolar and venular caliber, fractal dimension, branching angle, and vessel tortuosity were evaluated using a validated semi-automated program. Demographic and adverse event data were documented. Results172 images were recorded from 48 patients (n=29 cfLVAD, n=19 ESHF, mean age 54.2 ± 11.9 years). There were significant trends in retinal arteriolar caliber (B = -0.53 µm, 95% CI: -0.96 – -0.10, p = 0.016) and retinal fractal dimension parameters (B = 0.014, 95% CI: 0.001 – 0.002, p = 0.016) in linear mixed model regressions. Amongst cfLVAD patients, there was a significant association between the incidence of gastrointestinal bleeding and stepwise increases in retinal arteriolar-venular caliber ratio (HR: 3.03, 95% CI: 2.06 – 4.45, p = 0.005), a measure of arteriolar narrowing. ConclusionsWe have observed for the first time that alterations in retinal microvasculature in cfLVAD-supported patients may be associated with gastrointestinal bleeding. While understanding these temporal changes may predict future adverse events in cfLVAD-supported patients, further multi-center studies are required to confirm the associations observed.

3D Multiparametric Photoacoustic Computed Tomography of Primary and Metastatic Tumors in Living Mice.

Photoacoustic computed tomography (PACT), an emerging imaging modality in preclinical cancer research, can provide multiparametric 3D information about structures, physiological functions, and pharmacokinetics. Here, we demonstrate the use of high-definition 3D multiparametric PACT imaging of both primary and metastatic tumors in living mice to noninvasively monitor angiogenesis, carcinogenesis, hypoxia, and pharmacokinetics. The high-definition PACT system with a 1024-element hemispherical ultrasound transducer array provides an isotropic spatial resolution of 380 μm, an effective volumetric field-of-view of 12.8 mm × 12.8 mm × 12.8 mm without scanning, and an acquisition time of <30 s for a whole mouse body. Initially, we monitor the structural progression of the tumor microenvironment (e.g., angiogenesis and vessel tortuosity) after tumor cell inoculation. Then, we analyze the change in oxygen saturation of the tumor during carcinogenesis, verifying induced hypoxia in the tumor's core region. Finally, the whole-body pharmacokinetics are photoacoustically imaged after intravenous injection of micelle-loaded IR780 dye, and the in vivo PACT results are validated in vivo and ex vivo by fluorescence imaging. By employing the premium PACT system and applying multiparametric analyses to subcutaneous primary tumors and metastatic liver tumors, we demonstrate that this PACT system can provide multiparametric analyses for comprehensive cancer research.

First multicenter study evaluating the utility of the BENCHMARKTM BMXTM 81 large-bore access catheter in neurovascular interventions.

This study is the first multicentric report on the safety, efficacy, and technical performance of utilizing a large bore (0.081″ inner diameter) access catheter in neurovascular interventions. Data were retrospectively collected from seven sites in the United States for neurovascular procedures via large bore 0.081″ inner diameter access catheter (Benchmark BMX81, Penumbra, Inc.). The primary outcome was technical success, defined as the access catheter reaching its target vessel. Safety outcomes included periprocedural device-related and access site complications. There were 90 consecutive patients included. The median age of the patients was 63 years (IQR: 53, 68); 53% were female. The most common interventions were aneurysm embolization (33.3%), carotid stenting (12.2%), and arteriovenous malformation embolization (11.1%). The transradial approach was most used (56.7%), followed by transfemoral (41.1%). Challenging anatomic variations included severe vessel tortuosity (8/90, 8.9%), type 2 aortic arch (7/90, 7.8%), type 3 aortic arch (2/90, 2.2%), bovine arch (2/90, 2.2%), and severe angle (<30°) between the subclavian artery and target vessel (1/90, 1.1%). Technical success was achieved in 98.9% of the cases (89/90), with six cases requiring a switch from radial to femoral (6.7%) and one case from femoral to radial (1.1%). There were no access site complications or complications related to the 0.081″ catheter. Two postprocedural complications occurred (2.2%), unrelated to the access catheter. The BMX™ 81 large-bore access catheters was safe and effective in both radial and femoral access across a wide range of neurovascular procedures, achieving high technical success without any access site or device-related complications.

Experience with a novel high frequency optical coherence tomography device for intracoronary imaging: a case series.

Intravascular imaging, especially optical coherence tomography (OCT), has significantly improved percutaneous coronary intervention (PCI), yet its routine clinical application faces challenges. This case series introduces the Gentuity® High-Frequency Optical Coherence Tomography (HF-OCT), a novel device designed to enhance intracoronary imaging with a significantly faster pullback and smaller catheter size, potentially offering enhanced navigability in complex lesions. We aimed to assess the image quality of Gentuity® HF-OCT in complex vessel conditions, as well as presenting a case series to illustrate the application of the device in various clinical scenarios. In this case series, we included all patients who underwent intracoronary HF-OCT imaging at our center. The primary endpoint was image quality assessed by clear image length (CIL). Image quality was assessed in relation to (1) lesion severity assessed by minimum lumen area (MLA); (2) vessel size, differentiating between larger (diameter ≥ 4 mm) and smaller vessel segments; (3) pre- vs. post-PCI conditions, and (4) vessel tortuosity, categorized into none, moderate, and severe. Twenty-four HF-OCT runs from 14 patients were included. No significant differences in CIL were observed across lesion severity terciles (p = 0.449), between small and large vessel segments [mean CIL% difference 1.3%; confidence interval (CI), -9.3 to 11.8; p = 0.802], and pre- vs. post-PCI conditions (mean CIL difference -3.9 mm; CI, -14.0 to 6.1; p = 0.373). Vessel tortuosity significantly impacted image quality, with clear reductions in CIL observed in cases of moderate (74.8; CI, 73.5 to 76.0; vs. 63.9; CI, 56.2 to 71.5; p = 0.043) and severe tortuosity (74.8; CI, 73.5 to 76.0; vs. 65.0; CI, 62.1 to 67.9; p = 0.002) compared to vessels with no tortuosity. Overall, the HF-OCT demonstrated excellent catheter deliverability and crossability, with very satisfactory image quality and no significant adverse events. The Gentuity® HF-OCT is a new OCT device capable of navigating both small- and large-diameter vessels, with similar image quality, but vessel tortuosity seems to have an impact on image quality. It appears to be as usable as conventional OCT for pre-PCI diagnosis and OCT-guided PCI, potentially bringing additional benefits in terms of deliverability, lesion crossover and ease of use in routine clinical practice.

Neurological abnormalities in individuals with Marfan syndrome: results from a genetically confirmed Italian cohort.

Neurological abnormalities have been frequently reported in individuals with Marfan Syndrome (MFS). However, available data relies solely on retrospective studies predating current diagnostic criteria. Cross-sectional study comprehensively investigating neurological abnormalities within a prospective cohort of adults (≥ 18years) with genetically confirmed MFS referred to an Italian hub center for heritable connective tissue diseases (Jan. 1st - Nov. 15th, 2021). We included a total of 38 individuals (53% female). The commonest neurological symptom was migraine (58%), usually without aura (73%). Neuropsychological testing was generally unremarkable, whilst anxiety and depression were highly prevalent within our cohort (42% and 34%, respectively). The most frequent brain parenchymal abnormality was the presence of cortico-subcortical hypointense spots on brain MRI T2* Gradient-Echo sequences (39%), which were found only in patients with a prior history of aortic surgery. Migraineurs had a higher frequency of brain vessels tortuosity vs. individuals without migraine (73% vs. 31%; p = 0.027) and showed higher average and maximum tortuosity indexes in both anterior and posterior circulation brain vessels (all p < 0.05). At univariate regression analysis, the presence of brain vessels tortuosity was significantly associated with a higher risk of migraine (OR 5.87, CI 95% 1.42-24.11; p = 0.014). Our study confirms that neurological abnormalities are frequent in individuals with MFS. While migraine appears to be associated with brain vessels tortuosity, brain parenchymal abnormalities are typical of individuals with a prior history of aortic surgery. Larger prospective studies are needed to understand the relationship between parenchymal abnormalities and long-term cognitive outcomes.

Association of combination tumor texture and vessel tortuosity with progression free survival across PD-L1 subgroups in durvalumab treated non-small cell lung cancer (NSCLC): Blinded validation results from CP1108.

8600 Background: Immunotherapy (IO) has shown a durable response with minimal toxicity in the treatment of metastatic NSCLC. However, only 30-50% of these patients (pts) actually respond. Despite initial optimism surrounding PD-L1 expression as a potential biomarker, IO provides benefit across PD-L1 low (&lt;25%) and high (≥25%) status. This highlights a critical need for more effective biomarkers to guide treatment decisions. Here, we present blinded validation results of a CT-based biomarker of change in quantitative vessel tortuosity (1) (Δ-QVT) and texture radiomics (2) (Δ-Rad) between baseline (B) and 6 weeks post-treatment (TP1) for predicting response, overall survival (OS) and progression free survival (PFS) in CP1108 (NCT01693562). Methods: CT scans at B and TP1 were retrospectively analyzed from two studies (a) a multi-center training set (Str, N=110) of metastatic NSCLC pts treated with first line IO and (b) a blinded NSCLC cohort of N = 151 pts treated with Durvalumab in CP1108 study (Sv). In Sv, N=75 pts were PD-L1 high (Sv+) whereas N=65 pts were PD-L1 low (Sv-). An in-house MATLAB based algorithm was used to extract intra-tumoral, peri-tumoral texture and QVT features from up to two largest measurable tumors in each CT. A classifier (MCombo) was trained on Str to predict best overall response defined as per the RECIST v1.1 criteria using combination of Δ-QVT and Δ-Rad features. Area under the receiver operating characteristic (AUC) was used to evaluate MCombo against RECIST response whereas univariable and multivariable Cox regression models with log-rank test, hazard ratio (HR) with confidence interval (CI) and concordance index (C-index) were used to study the association of MCombo with OS and PFS in Sv, Sv+, and Sv-. Results: MCombo predicted objective response with an AUC of 0.78 in Sv and was statistically significantly associated with PFS (Table) in Sv, Sv+, and Sv-. MCombo was associated with OS in Sv, Sv+, but not in Sv-. Multivariable analysis with PD-L1 status, histological subtype, ECOG status, liver metastasis, line of therapy and sex showed independent association of MCombo across OS and PFS. Conclusions: Our results indicate that combination of radiomics and vessel tortuosity biomarker from CT is independently prognostic of response and PFS across PD-L1 levels. Prospective validation of this biomarker is needed. 1. Alilou et al. Sci Adv 2022. 2. Khorrami et al. Cancer Immunol Res 2020. [Table: see text]

Computational analysis of cancer cell adhesion in curved vessels affected by wall shear stress for prediction of metastatic spreading.

Introduction: The dynamics of circulating tumor cells (CTCs) within blood vessels play a pivotal role in predicting metastatic spreading of cancer within the body. However, the limited understanding and method to quantitatively investigate the influence of vascular architecture on CTC dynamics hinders our ability to predict metastatic process effectively. To address this limitation, the present study was conducted to investigate the influence of blood vessel tortuosity on the behaviour of CTCs, focusing specifically on establishing methods and examining the role of shear stress in CTC-vessel wall interactions and its subsequent impact on metastasis. Methods: We computationally simulated CTC behaviour under various shear stress conditions induced by vessel tortuosity. Our computational model, based on the lattice Boltzmann method (LBM) and a coarse-grained spectrin-link membrane model, efficiently simulates blood plasma dynamics and CTC deformability. The model incorporates fluid-structure interactions and receptor-ligand interactions crucial for CTC adhesion using the immersed boundary method (IBM). Results: Our findings reveal that uniform shear stress in straight vessels leads to predictable CTC-vessel interactions, whereas in curved vessels, asymmetrical flow patterns and altered shear stress create distinct adhesion dynamics, potentially influencing CTC extravasation. Quantitative analysis shows a 25% decrease in the wall shear stress in low-shear regions and a 58.5% increase in the high-shear region. We observed high-shear regions in curved vessels to be potential sites for increased CTC adhesion and extravasation, facilitated by elevated endothelial expression of adhesion molecules. This phenomenon correlates with the increased number of adhesion bonds, which rises to approximately 40 in high-shear regions, compared to around 12 for straight vessels and approximately 5-6 in low-shear regions. The findings also indicate an optimal cellular stiffness necessary for successful CTC extravasation in curved vessels. Discussion: By the quantitative assessment of the risk of CTC extravasation as a function of vessel tortuosity, our study offers a novel tool for the prediction of metastasis risk to support the development of personalized therapeutic interventions based on individual vascular characteristics and tumor cell properties.

Differential artery-vein analysis improves the OCTA classification of diabetic retinopathy.

This study investigates the impact of differential artery-vein (AV) analysis in optical coherence tomography angiography (OCTA) on machine learning classification of diabetic retinopathy (DR). Leveraging deep learning for arterial-venous area (AVA) segmentation, six quantitative features, including perfusion intensity density (PID), blood vessel density (BVD), vessel area flux (VAF), blood vessel caliber (BVC), blood vessel tortuosity (BVT), and vessel perimeter index (VPI) features, were derived from OCTA images before and after AV differentiation. A support vector machine (SVM) classifier was utilized to assess both binary and multiclass classifications of control, diabetic patients without DR (NoDR), mild DR, moderate DR, and severe DR groups. Initially, one-region features, i.e., quantitative features extracted from the entire OCTA, were evaluated for DR classification. Differential AV analysis improved classification accuracies from 78.86% to 87.63% and from 79.62% to 85.66% for binary and multiclass classifications, respectively. Additionally, three-region features derived from the entire image, parafovea, and perifovea, were incorporated for DR classification. Differential AV analysis further enhanced classification accuracies from 84.43% to 93.33% and from 83.40% to 89.25% for binary and multiclass classifications, respectively. These findings highlight the potential of differential AV analysis in augmenting disease diagnosis and treatment assessment using OCTA.

Scanning optoacoustic angiography for assessing structural and functional alterations in superficial vasculature of patients with post-thrombotic syndrome: A pilot study

This study highlights the potential of scanning optoacoustic angiography (OA) in identifying alterations of superficial vasculature in patients with post-thrombotic syndrome (PTS) of the foot, a venous stress disorder associated with significant morbidity developing from long-term effects of deep venous thrombosis. The traditional angiography methods available in the clinics are not capable of reliably assessing the state of peripheral veins that provide blood outflow from the skin, a key hallmark of personalized risks of PTS formation after venous thrombosis. Our findings indicate that OA can detect an increase in blood volume, diameter, and tortuosity of superficial blood vessels. The inability to spatially separate vascular plexuses of the dermis and subcutaneous adipose tissue serves as a crucial criterion for distinguishing PTS from normal vasculature. Furthermore, our study demonstrates the ability of scanning optoacoustic angiography to detect blood filling decrease in an elevated limb position versus increase in a lowered position.

Hemodynamic Characteristics of Tortuous Microvessels Using High-Fidelity Red Blood Cell Resolved Simulations

Introduction: Tortuous microvessels are characteristic of microvascular remodeling associated with numerous physiological and pathological scenarios. These vessels have unique morphology compared to straight vessels, the latter being the subject of extensive flow modeling studies over the past few decades. Three-dimensional hemodynamics in tortuous microvessels influenced by red blood cell (RBCs), however, remain largely unknown and important questions remain. Is blood viscosity influenced by vessel tortuosity? Do RBC flow dynamics cause localized hematocrit variations in tortuous vessels? How do these dynamics affect wall shear stress patterns and the near-wall cell-free layer? Previous work has connected physiological function to tortuosity1, while other recent work has shown how RBC dynamics and vessel complexity can influence hemodynamics2. Such findings drive our hypothesis that unique hemodynamic characteristics exist in tortuous microvessels compared to straight vessels. Revealing such differences and answering the above questions requires 3D RBC-resolved simulations. The objective of this work is to investigate the hemodynamic characteristics of tortuous microvessels using high-fidelity red blood cell (RBC) resolved simulations and real image data. Methods: High fidelity RBC resolved simulations were performed using a 3D immersed boundary method (IBM) based fluid dynamic solver3. A tortuous microvessel is constructed in 3D based on imaging of a rat mesenteric microvascular network post angiogenic remodeling. The diameter and length of the vessel are 20 μm and 930 μm, respectively. Simulations were performed spanning a range of physiological shear rates (SR) and overall hematocrit levels (Ht). Output simulation data is used to parametrically quantify characteristics of apparent viscosity, local hematocrit variations, time-averaged wall shear stress (TAWSS) and cell free layer (CFL) patterns due to vessel tortuosity. Data and Results: The findings show how curvature can increase apparent viscosity to different degrees based on overall Ht &amp; SR (max 236% increase), with local variations occurring over the vessel length at sites of curvature changes (max 2.25cP change). Because of RBC flow patterns, local variations in tube hematocrit are found to occur which result in local curvature-dependent variations in the Fahraeus effect. We further characterize dependencies of the CFL and TAWSS on Ht &amp; SR and resultant lengthwise 3D spatial variations along the vessel, and demonstrate correlation patterns between these two quantities as influenced by tortuosity. Conclusions: New findings from this work reveal significant dependency of hemodynamic parameters and spatial variations on vessel tortuosity. The results provide new information to better understand the role of vessel tortuosity in physiological and pathological processes, as well as help improve reduced-order models. NSF CBET 2309559, NIH R21HL159501, and Expanse at the San Diego Supercomputer Center per NSF Accelerate Award BIO230073. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Inflow stabilization for hemodynamic simulations using Stokesian regions

Blood flow simulations in three-dimensional space pose the challenge of isolating the vascular domain of interest, which introduces artificial interfaces, both upstream and downstream, where boundary conditions must be prescribed. Vessel curvature, tortuosity, and blood flow pulsatility contribute to the complexity of performing these simulations. A common practice in defining boundary conditions is to prescribe Neumann-like boundary conditions over these boundaries. A typical numerical problem in such a setting is associated with the unbounded nature of the kinetic energy that enters into the system, either through antegrade upstream flow or through downstream retrograde flow. Lack of energy control in the continuum problem may become a source of numerical instability, resulting in corrupted simulations. In this work, we propose a novel approach to avoid these instabilities by considering a bulk fluid with specific properties in a small portion of the domain in the vicinity of such boundaries. More precisely, the convective term from the governing equations is nullified in these domain extensions, resulting in Stokesian regions. In contrast to the classical approach based on the inclusion of straight long extensions to allow flow development, the proposed approach involves dealing with small regions whose length is smaller than the vessel diameter, to control the kinetic energy with near zero added computational cost. This stabilization strategy is investigated within the context of the Transversally Enriched Pipe Element Method, which makes the implementation straightforward. Academic examples and patient-specific vascular geometries are employed to illustrate the performance of the proposed stabilization strategy.

A Multi-Stage Approach for Cardiovascular Risk Assessment from Retinal Images Using an Amalgamation of Deep Learning and Computer Vision Techniques.

Cardiovascular diseases (CVDs) are a leading cause of mortality worldwide. Early detection and effective risk assessment are crucial for implementing preventive measures and improving patient outcomes for CVDs. This work presents a novel approach to CVD risk assessment using fundus images, leveraging the inherent connection between retinal microvascular changes and systemic vascular health. This study aims to develop a predictive model for the early detection of CVDs by evaluating retinal vascular parameters. This methodology integrates both handcrafted features derived through mathematical computation and retinal vascular patterns extracted by artificial intelligence (AI) models. By combining these approaches, we seek to enhance the accuracy and reliability of CVD risk prediction in individuals. The methodology integrates state-of-the-art computer vision algorithms and AI techniques in a multi-stage architecture to extract relevant features from retinal fundus images. These features encompass a range of vascular parameters, including vessel caliber, tortuosity, and branching patterns. Additionally, a deep learning (DL)-based binary classification model is incorporated to enhance predictive accuracy. A dataset comprising fundus images and comprehensive metadata from the clinical trials conducted is utilized for training and validation. The proposed approach demonstrates promising results in the early prediction of CVD risk factors. The interpretability of the approach is enhanced through visualization techniques that highlight the regions of interest within the fundus images that are contributing to the risk predictions. Furthermore, the validation conducted in the clinical trials and the performance analysis of the proposed approach shows the potential to provide early and accurate predictions. The proposed system not only aids in risk stratification but also serves as a valuable tool for identifying vascular abnormalities that may precede overt cardiovascular events. The approach has achieved an accuracy of 85% and the findings of this study underscore the feasibility and efficacy of leveraging fundus images for cardiovascular risk assessment. As a non-invasive and cost-effective modality, fundus image analysis presents a scalable solution for population-wide screening programs. This research contributes to the evolving landscape of precision medicine by providing an innovative tool for proactive cardiovascular health management. Future work will focus on refining the solution's robustness, exploring additional risk factors, and validating its performance in additional and diverse clinical settings.

Transcarotid vascular access for transcatheter aortic valve implantation: is choosing the left side always right?

BackgroundThe transcarotid (TC) vascular access for transcatheter aortic valve implantation (TAVI) has emerged as the first-choice alternative to the transfemoral access, in patients unsuitable for the latter. The use of both the left and right common carotid arteries (CCAs) for TC-TAVI has been described, but the optimal side is subject to debate. We conducted this pilot study to compare the level of vessel tortuosity and plaque burden from either the left CCA to the aortic annulus, or the right CCA to the aortic annulus, considering them as surrogates for technical and procedural complexity.MethodsConsecutive patients who underwent TC-TAVI between 2018 and 2021 in our institution were included. Using three-dimensional reconstruction, pre-TAVI neck and chest computed tomography angiography exams were reviewed to assess the tortuosity index (TI), sum of angles metric, as well as plaque burden, between each CCA and the aortic annulus.ResultsWe included 46 patients who underwent TC-TAVI. No significant difference regarding the mean TIs between the left and right sides (respectively 1.20 and 1.19, p = 0.82), the mean sum of angles (left side: 396°, right side: 384°, p = 0.27), and arterial plaque burden (arterial plaque found in 30% of left CCAs and 45% of right CCAs, p = 0.19) was found.ConclusionsWe found no convincing data favoring the use of one particular access side over the other one. The choice of the CCA side in TC-TAVI should to be made on a case-by-case basis, in a multidisciplinary fashion, and may also depend on the operators’ experience.

210 Defining the Learning Curve for Cerebral Angiography Using a Novel Web-Based Feedback Application and Head-Mounted Video Review

INTRODUCTION: The milestones that a resident or fellow should reach to achieve competence in cerebral angiography have yet to be defined. METHODS: Two neurosurgical residents were given a written knowledge exam before and after rotating on the endovascular service. Cerebral angiography diagnostic and treatment cases were prospectively collected in a novel web-based, multi-institutional feedback application. These residents performed cerebral angiography cases under graduated supervision while wearing head-mounted cameras for subsequent review with direct feedback. Residents and reviewers independently utilized CaseCurve, a novel neurosurgical resident performance tracking application, as a platform for performance rating. Numerical scores were assigned ranging from 1 (novice) to 5 (masterful) in the following categories: access, catheter navigation, table operation, closure, efficiency, finesse, angiographic interpretation, and catheter knowledge. The number of times the supervising surgeon had to take over the case was recorded. Arch anatomy and vessel tortuosity were graded. Operative videos were analyzed for operator inefficiencies and time metrics for sheath insertion and target vessel selection. Angiographic efficiency was assessed with fluoroscopic doses/times and procedural durations. RESULTS: Both residents demonstrated improvement in cognitive performance as measured by written assessment scores. Significant improvements were observed in technical performance as measured by numerical scores assigned by self-evaluation, faculty review, objective measures of angiographic efficiency, and the number of times the supervising surgeon had to take over the procedure. Concordance between faculty and resident self-evaluations was 74.2%, with residents underestimating their performance in 21% and overestimating in 5%. CONCLUSIONS: There is significant educational value for the trainer and trainee offered by our novel web-based feedback application and head-mounted video review. This data allows for accurate assessments of skill acquisition and delineation of appropriate milestones/learning categories for trainees in endovascular neurosurgery.

Impact of image resolution on retinal vessel tortuosity assessment

Impact of image resolution on retinal vessel tortuosity assessment