Study protocol of validating a numerical model to assess the blood flow in the circle of Willis

Introduction We developed a zero-dimensional (0D) model to assess the patient-specific haemodynamics in the circle of Willis (CoW). Similar numerical models for simulating the cerebral blood flow (CBF) had only been validated qualitatively in healthy volunteers by magnetic resonance (MR) angiography and transcranial Doppler (TCD). This study aims to validate whether a numerical model can simulate patient-specific blood flow in the CoW under pathological conditions. Methods and analysis This study is a diagnostic accuracy study. We aim to collect data from a previously performed prospective study that involved patients with aneurysmal subarachnoid haemorrhage (aSAH) receiving both TCD and brain Computerd Tomography angiography (CTA) at the same day. The cerebral flow velocities are calculated by the 0D model, based on the vessel diameters measured on the CTA of each patient. In this study, TCD is considered the gold standard for measuring flow velocity in the CoW. The agreement will be analysed using Pearson correlation coefficients. Ethics and dissemination This study protocol has been approved by the Medical Ethics Review Board of the University Medical Center Groningen: METc2019/103. The results will be submitted to an international scientific journal for peer-reviewed publication. Trial registration number NL8114

Patient-Specific Cerebral Blood Flow Simulation Based on Commonly Available Clinical Datasets

Cerebral hemodynamics play an important role in the development of cerebrovascular diseases. In this work, we propose a numerical framework for modeling patient-specific cerebral blood flow, using commonly available clinical datasets. Our hemodynamic model was developed using Simscape Fluids library in Simulink, based on a block diagram language. Medical imaging data obtained from computerized tomography angiography (CTA) in 59 patients with aneurysmal subarachnoid hemorrhage was used to extract arterial geometry parameters. Flow information obtained from transcranial Doppler (TCD) measurement was employed to calibrate input parameters of the hemodynamic model. The results show that the proposed numerical model can reproduce blood flow in the circle of Willis (CoW) per patient per measurement set. The resistance at the distal end of each terminal branch was the predominant parameter for the flow distribution in the CoW. The proposed model may be a promising tool for assessing cerebral hemodynamics in patients with cerebrovascular disease

Role of pre-operative frailty status in relation to outcome after carotid endarterectomy:a systematic review

Carotid endarterectomy (CEA) is a surgical treatment option to prevent ischemic cerebrovascular accidents. Patients that present with pre-operative frailty might have an elevated risk for unfavorable outcomes after the CEA. A systematic search, using Medline, Embase, Web of Science and Cochrane Database, was performed for relevant literature on frailty in patients undergoing CEA. The study protocol was registered with PROSPERO (CRD42020190345). Eight articles were included. The pooled prevalence for pre-operative frailty was 23.9% (95% CI: 12.98-34.82). A difference in the incidence of complications between frail and non-frail patients (6.4% vs. 5.2%, respectively) and a difference in hospital length of stay [2 (IQR: 2-3) days vs. 1 (IQR: 1-2) day, respectively] were described. The 30-day mortality after CEA was 0.6% for non-frail patients, 2.6% for frail patients, and 4.9% for very frail patients (P 0.001). For 3-year mortality, a 1.5-fold increased risk was found for frail patients (OR 1.7, 95% CI: 1.4-2.0) and a &gt;2.5-fold increased risk for very frail patients (OR 2.6, 95% CI: 2.2-3.1). In conclusion, this review shows the impact of frailty on outcome after CEA. Pre-operative frailty assessment with a validated, multi-domain tool should be implemented in the clinical setting as it will provide information on post-operative surgical outcomes and mortality risk but also frailty trajectory and cognitive decline.</p

The Role of Hemodynamics through the Circle of Willis in the Development of Intracranial Aneurysm:A Systematic Review of Numerical Models

Background: The role of regional hemodynamics in the intracranial aneurysmal formation, growth, and rupture has been widely discussed based on numerical models over the past decades. Variation of the circle of Willis (CoW), which results in hemodynamic changes, is associated with the aneurysmal formation and rupture. However, such correlation has not been further clarified yet. The aim of this systematic review is to investigate whether simulated hemodynamic indices of the CoW are relevant to the formation, growth, or rupture of intracranial aneurysm. Methods: We conducted a review of MEDLINE, Web of Science, and EMBASE for studies on the correlation between hemodynamics indices of the CoW derived from numerical models and intracranial aneurysm up to December 2020 in compliance with PRISMA guidelines. Results: Three case reports out of 1046 publications met our inclusion and exclusion criteria, reporting 13 aneurysms in six patients. Eleven aneurysms were unruptured, and the state of the other two aneurysms was unknown. Wall shear stress, oscillatory shear index, von-Mises tension, flow velocity, and flow rate were reported as hemodynamic indices. Due to limited cases and significant heterogeneity between study settings, meta-analysis could not be performed. Conclusion: Numerical models can provide comprehensive information on the cerebral blood flow as well as local flow characteristics in the intracranial aneurysm. Based on only three case reports, no firm conclusion can be drawn regarding the correlation between hemodynamic parameters in the CoW derived from numerical models and aneurysmal formation or rupture. Due to the inherent nature of numerical models, more sensitive analysis and rigorous validations are required to determine its measurement error and thus extend their application into clinical practice for personalized management. Prospero registration number: CRD42021125169

Arterial thrombotic complications in COVID-19 patients

The coronavirus disease 2019 (COVID-19), a viral respiratory illness caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been described to predispose to thrombotic disease in both the venous and arterial circulations. We report four cases of an acute arterial occlusion in COVID-19 patients and literature review on the occurrence of arterial thrombosis in patients with COVID-19. Our findings demonstrate that physicians should be vigilant for signs of thrombotic complications in both hospitalized and new COVID-19 patients

Outcomes after endovascular mechanical thrombectomy in occluded vascular access used for dialysis purposes

PURPOSE: Endovascular mechanical thrombectomy using the AngioJet™ system can be considered to reestablish patency in occluded vascular access. The aim of this study was to review our results for endovascular mechanical thrombectomy using the AngioJet™ system in patients with arteriovenous fistulae (AVF) and arteriovenous grafts (AVG). METHODS: Data collected in a database of patients requiring hemodialysis for renal failure were analyzed. Patients who underwent endovascular mechanical thrombectomy procedures with the AngioJet™ system for occlusion of vascular access were included. Clinical and technical success rates and patency rates were calculated. Multivariate analysis was used to identify factors of influence. RESULTS: A total of 92 AngioJet™ procedures in 60 patients with thrombosed vascular access were reviewed during a mean follow-up period of 21.5 months in patients with an AVF and 11.9 months in patients with an AVG. Technical and clinical success was achieved in 92.6% of AVF cases and 92.0 and 90.8% of AVG cases with an AVG, respectively. Significantly higher primary and primary-assisted patency rates were observed in the AVF group. Multivariate regression analysis indicated that left-sided vascular access and female sex were independent predictors for failure regarding primary patency in AVG patients. Immunosuppressive drugs and older age were negative predictors for secondary patency in AVG patients. CONCLUSIONS: The AngioJet™ system can be deemed an effective technique to reestablish patency in occluded vascular access with minimal use of central venous catheters for dialysis. Good technical and clinical success rates were achieved with acceptable patency rates, especially in AVF patients

Spatial coefficient of variation of arterial spin labeling MRI as a cerebrovascular correlate of carotid occlusive disease

Clinical interpretation of arterial spin labeling (ASL) perfusion MRI in cerebrovascular disease remains challenging mainly because of the method’s sensitivity to concomitant contributions from both intravascular and tissue compartments. While acquisition of multi-delay images can differentiate between the two contributions, the prolonged acquisition is prone to artifacts and not practical for clinical applications. Here, the utility of the spatial coefficient of variation (sCoV) of a single-delay ASL image as a marker of the intravascular contribution was evaluated by testing the hypothesis that sCoV can detect the effects of differences in label arrival times between ipsi- and contra-lateral hemispheres even in the absence of a hemispheric difference in CBF. Hemispheric lateralization values for sCoV and CBF were computed from ASL images acquired on 28 patients (age 73.9 ± 10.2 years, 8 women) with asymptomatic unilateral carotid occlusion. The results showed that sCoV lateralization predicted the occluded side with 96.4% sensitivity, missing only 1 patient. In contrast, the sensitivity of the CBF lateralization was 71.4%, with 8 patients showing no difference in CBF between hemispheres. The findings demonstrate the potential clinical utility of sCoV as a cerebrovascular correlate of large vessel disease. Using sCoV in tandem with CBF, vascular information can be obtained in image processing without the need for additional scan-time

Treatment of the extracranial carotid artery in tandem lesions during endovascular treatment of acute ischemic stroke:a systematic review and meta-analysis

Endovascular treatment (EVT) is the standard treatment for patients with an acute ischemic stroke due to occlusion of large vessel occlusion (LVO). In 20% of patients, concomitant extracranial internal carotid artery (EICA) lesion is present. These tandem lesions (TL) offer a technical challenge. The treatment strategy for the treatment of the ipsilateral EICA is unclear. The aim of this review is to compare two treatment strategies for TL during EVT: balloon angioplasty (BA) only and immediate carotid artery stenting (iCAS). A systematic review and meta-analysis was performed. Data for each included study was extracted. For comparative studies a meta-analysis was performed. Functional outcome was expressed with the modified Rankin scale and safety endpoints were mortality and symptomatic intracranial hemorrhage (sICH). A total of 72 full text articles evaluating treatment of TL during EVT were screened. Sixteen iCAS and five comparative studies were included for meta-analysis. 53% of patients undergoing iCAS during EVT had good functional outcome in comparison to 45% of patients who underwent only BA. Mortality was comparable at 16% for both groups. The incidences of sICH were 8% and 4% for iCAS and BA respectively. In the meta-analysis, iCAS was associated with good functional outcome, with no significant differences in mortality and sICH with compared to BA. This study shows that treatment with iCAS of a simultaneously ipsilateral EICA lesion during EVT is associated with a favorable functional outcome compared to BA only with no significant difference in mortality or sICH. No conclusion could be drawn about the intracranial or extracranial first approach due to scarce of data. More studies are needed to determine long-term neurological outcomes, the necessity of re-interventions and optimal technical approach (intracranial or extracranial first)

Brachial and Axillary Artery Vascular Access for Endovascular Interventions

Background: Endovascular access is usually achieved through the common femoral artery due to its large size and accessibility. Access through the upper extremity can however be necessary due to anatomic reasons, obesity, or peripheral arterial disease. The 2 main methods of access are surgical cutdown and percutaneous puncture. In this single-centre retrospective cohort study we compared complication risks for both surgical cutdown and percutaneous puncture of an upper arm approach. Materials and Methods: Data was obtained from patients receiving endovascular access through the brachial or axillary artery between 2005 and 2018. A total of 109 patients were included. Patient demographics including age, sex, medical history, smoking status, and actual medication were registered, as well as postoperative complications including hematoma, thrombosis, dissection, infection, pseudoaneurysm, nerve injury, reoperation, and readmission. Results: Access was achieved through surgical cutdown in 53% (n = 58) and through percutaneous puncture in 47% (n = 51) of patients. Fifty-eight percent (n = 63) received access via the brachial artery (BA) and 42% (n = 46) via the axillary artery. Complication rate was 25.0% (3 of 12) for surgical cutdown via the BA, 29.4% (15 of 51) for percutaneous puncture via the BA, and 10.9% (5 of 46) for surgical cutdown via the axillary artery. Major complication rate was 8.3% (1 of 12) for surgical cutdown via the BA, 13.7% (7 of 51) for percutaneous puncture via the BA, and 4.3% (2 of 46) for surgical cutdown via the axillary artery. There was no association between baseline patient characteristics and complication rate. Conclusions: In this nonrandomized retrospective study, surgical cutdown via the axillary artery was the safest option with fewest complications, but selection of patients may have blurred the results. Surgical cutdown and percutaneous puncture seem equally safe in terms of complication rate in the BA

Validation of a cerebral hemodynamic model with personalized calibration in patients with aneurysmal subarachnoid hemorrhage

This study aims to validate a numerical model developed for assessing personalized circle of Willis (CoW) hemodynamics under pathological conditions. Based on 66 computed tomography angiography images, investigations were obtained from 43 acute aneurysmal subarachnoid hemorrhage (aSAH) patients from a local neurovascular center. The mean flow velocity of each artery in the CoW measured using transcranial Doppler (TCD) and simulated by the numerical model was obtained for comparison. The intraclass correlation coefficient (ICC) over all cerebral arteries for TCD and the numerical model was 0.88 (N = 561; 95% CI 0.84–0.90). In a subgroup of patients who had developed delayed cerebral ischemia (DCI), the ICC had decreased to 0.72 but remained constant with respect to changes in blood pressure, Fisher grade, and location of ruptured aneurysm. Our numerical model showed good agreement with TCD in assessing the flow velocity in the CoW of patients with aSAH. In conclusion, the proposed model can satisfactorily reproduce the cerebral hemodynamics under aSAH conditions by personalizing the numerical model with TCD measurements. Clinical trial registration: [http://www.trialregister.nl/], identifier [NL8114]