P.193 Competitive Flow Diversion: Proposed Classification System

Background: Competitive flow diversion (CFD) is a novel application of flow diversion stenting (FDS), redirecting flow into a normal artery proximal or distal to the aneurysmal parent artery. A classification system for CFD has not been previously reported. Methods: Report of operative technique and novel classification system for CFD. Results: A patient with subarachnoid haemorrhage and three aneurysms arising from the Pcomm-P1 complex, was treated with endovascular coiling and CFD. The PCOM aneurysm was coiled. Two aneurysms arose from the distal right P1- PCA. After a failed attempt to treat with FDS across the P1-PCA, the P1-aneurysms were successfully treated with CFD distal to the P1-PCA, from Pcomm to P2. Over 12 months, CFD redirected flow via ICA-Pcomm-P2, reducing the size of the P1-PCA, obliterating the P1-aneurysms. Herein, we classify competitive flow diversion into two types. Type I CFD is when the parent artery harbouring the aneurysm is “jailed” proximally. Type II CFD occurs when flow is diverted from the parent artery distal to the aneurysm origin. Conclusions: Herein, we propose a novel classification for CFD. We describe the first case of aneurysm occlusion in the circle of Willis with Type II CFD, and use of CFD for the treatment of multiple adjacent aneurysms.

Dach1 Extends Artery Networks and Protects Against Cardiac Injury

Rationale: Coronary artery disease (CAD) is the leading cause of death worldwide, but there are currently no methods to stimulate artery growth or regeneration in diseased hearts. Studying how arteries are built during development could illuminate strategies for re-building these vessels during ischemic heart disease. We previously found that Dach1 deletion in mouse embryos resulted in small coronary arteries. However, it was not known whether Dach1 gain-of-function would be sufficient to increase arterial vessels and whether this could benefit injury responses. Objective: We investigated how Dach1 overexpression in endothelial cells affected transcription and artery differentiation, and how it influenced recovery from myocardial infarction (MI). Methods and Results: Dach1 was genetically overexpressed in coronary endothelial cells (ECs) in either developing or adult hearts using ApjCreER. This increased the length and number of arterial end branches expanded arteries during development, in both the heart and retina, by inducing capillary ECs to differentiate and contribute to growing arteries. Single-cell RNA sequencing (scRNAseq) of ECs undergoing Dach1-induced arterial specification indicated that it potentiated normal artery differentiation, rather than functioning as a master regulator of artery cell fate. ScRNAseq also showed that normal arterial differentiation is accompanied by repression of lipid metabolism genes, which were also repressed by Dach1. In adults, Dach1 overexpression did not cause a statistically significant change artery structure prior to injury, but increased the number of perfused arteries in the injury zone post-MI. Conclusions: Our data demonstrate that increasing Dach1 is a novel method for driving artery specification and extending arterial branches, which could be explored as a means of mitigating the effects of CAD.

Usefulness of black-blood magnetic resonance angiography generated from vessel wall imaging after the stent-assisted treatment of intracranial arterial diseases

Purpose After stent-assisted treatment for intracranial diseases, three-dimensional time-of-flight magnetic resonance angiography is a noninvasive follow-up method, but susceptibility artifacts prevent accurate evaluations of stented arteries. Sampling perfection with application-optimized contrast using different flip angle evolution (SPACE) sequence often used for vessel wall imaging is less susceptible to susceptibility artifacts, since it is a spin-echo sequence. Hence, we evaluated the feasibility of black-blood magnetic resonance angiography generated from vessel wall imaging data obtained using the SPACE sequence in the depiction of stented arteries by comparing with three-dimensional time-of-flight magnetic resonance angiography and digital subtraction angiography. Methods Our study group comprised 11 consecutive patients. For both three-dimensional time-of-flight magnetic resonance angiography and black-blood magnetic resonance angiography, the contrast ratio obtained from the stented artery and the normal artery proximal to the stent were calculated. And the depiction of stented arteries was visually evaluated. Additionally, the relative diameter index obtained from the stented artery and the normal artery proximal to the stent were calculated for three-dimensional time-of-flight magnetic resonance angiography, black-blood magnetic resonance angiography and digital subtraction angiography. Results The contrast ratio of the stented artery was significantly lower than that of the normal artery on three-dimensional time-of-flight magnetic resonance angiography, but no significant difference was seen using black-blood magnetic resonance angiography. Regarding both the diameter index and the visual assessment score, black-blood magnetic resonance angiography was significantly better than three-dimensional time-of-flight magnetic resonance angiography. On black-blood magnetic resonance angiography, the diameter index was equal to that of digital subtraction angiography, and the flow signal was homogeneous and continuous in most the cases.

Study of Arterial Function and Remodelling by Using Radiofrequency and a New Multidirectional Doppler Technology

Introduction: Atherosclerosis is the underlying cause of a cardiovascular disease epidemic worldwide. The understanding of normal artery structure and function and the initial disarrangements conducting to atherosclerosis is of key relevance to develop preventive interventions based on a rational study of arterial structural and functional parameters, their pathologic behaviour and response to therapeutic interventions. New US approaches enable a precise evaluation of the forces and stimuli acting on the arterial wall and measure its responses precisely in different clinical stages of the arterial atherosclerotic disease and a better assessment of the efficacy or not of different therapeutic interventions. The ability to analyse WSS hemodynamically and to measure it accurately is an essential basis for the assessment of the atherosclerotic risk in the general population. A new angle-independent technique, measuring and visualizing blood flow velocities in all directions, called Vector Flow Imaging (VFI), has been proposed. Systems are equipped with VFI based on a multi-angle transmission plane waves method, which allows a very high frame rate and a detailed visualization of complex flow.

Dach1 extends artery networks and protects against cardiac injury

Coronary artery disease (CAD) is the leading cause of death worldwide, but there are currently no available methods to stimulate growth or regeneration of artery networks in diseased hearts. Studying how arteries are built during embryonic development could illuminate strategies for re-building these vessels in the setting of ischemic heart disease. We previously found, using loss-of-function experiments, that the transcription factor Dach1 is required for coronary artery development in mouse embryos. Here, we report that Dach1 overexpression in endothelial cells (ECs) extended coronary arteries and improved survival and heart function in adult mice following myocardial infarction (MI). Dach1 overexpression increased the length and number of arterial end branches, in both heart and retinal vasculature, by causing additional capillary ECs to differentiate into arterial ECs and contribute to growing arteries. Single-cell RNA sequencing (scRNAseq) of ECs undergoing Dach1-induced arterial specification indicated that it potentiated normal artery differentiation, rather than functioning as a master regulator of artery cell fate. ScRNAseq also showed that normal arterial differentiation is accompanied by repression of lipid metabolism genes, which were also repressed by Dach1 prior to arterialization. Together, these results demonstrate that increasing the expression level of Dach1 is a novel pathway for driving specification of artery ECs and extending arterial vessels, which could be explored as a means of increasing artery coverage to mitigate the effects of CAD.

Automated Evaluation of Intracranial Vessel Morphology in Normal Versus Pediatric Moyamoya Disease

INTRODUCTION Evaluation of intracranial artery morphology plays an important role in diagnosing a variety of neurovascular diseases. In addition to clinical symptoms, diagnosis currently relies on qualitative rather than quantitative evaluation of vascular imaging sequences such as magnetic resonance angiography (MRA). However, previously described statistical cerebroarterial atlases have focused primarily on healthy adults and little information exists about what constitutes normal artery morphology in the pediatric population and across brain development. We aimed to quantitatively assess normal, age-related changes in artery morphology and compare normal morphology to that of children with Moyamoya disease (MMD). METHODS MRAs from 98 children (49 M/49F) aged .6 to 20 yr (median = 11.5 yr) with normal MRAs and and 18 children with radiographically confirmed MMD (10 M/8 F, median age = 7.1 yr) were retrospectively collected. All arteries were automatically segmented in both MRA datasets. Using an atlas-based approach, the radiuses of the main arteries of the anterior circulation (internal carotid artery (ICA), anterior cerebral artery (ACA), and middle cerebral artery (MCA)) and posterior circulation (PCA, BA) were measured at corresponding locations. Artery radii were compared between the 2 groups using MANCOVA with age and sex as covariates. RESULTS The artery radius was relatively consistent across age for all main arteries in normal patients. MANCOVA revealed that children with MMD exhibit significantly smaller ICA, MCA-M1, MCA-M2, and ACA radii (P < .001) compared to normal controls (mean vessel radii: ICA 1.27 vs 1.64 mm, MCA M1 0.92 vs 1.14 mm, MCA M2 0.66 vs 0.82 mm, ACA 0.72 vs 0.83 mm). There were no significant differences in the posterior circulation radii. CONCLUSION We present normal artery morphology data for children based on automatic segmentation of MRAs, and demonstrate that artery caliber is smaller in children with MMD. This resource will allow neurosurgeons to quantitatively assess MMD and the impact of bypass surgery on disease progression.

Carotid and vertebral injury study (CAVIS) technique for characterization of blunt traumatic aneurysms with reliability assessment

Traumatic aneurysms occur in up to 20% of blunt traumatic extracranial carotid artery injuries. Currently there is no standardized method for characterization of traumatic aneurysms. For the carotid and vertebral injury study (CAVIS), a prospective study of traumatic cerebrovascular injury, we established a method for aneurysm characterization and tested its reliability. Saccular aneurysm size was defined as the greatest linear distance between the expected location of the normal artery wall and the outer edge of the aneurysm lumen (“depth”). Fusiform aneurysm size was defined as the “depth” and longitudinal distance (“length”) paralleling the normal artery. The size of the aneurysm relative to the normal artery was also assessed. Reliability measurements were made using four raters who independently reviewed 15 computed tomographic angiograms (CTAs) and 13 digital subtraction angiograms (DSAs) demonstrating a traumatic aneurysm of the internal carotid artery. Raters categorized the aneurysms as either “saccular” or “fusiform” and made measurements. Five scans of each imaging modality were repeated to evaluate intra-rater reliability. Fleiss’s free-marginal multi-rater kappa (κ), Cohen’s kappa (κ), and interclass correlation coefficient (ICC) determined inter- and intra-rater reliability. Inter-rater agreement as to the aneurysm “shape” was almost perfect for CTA (κ = 0.82) and DSA (κ = 0.897). Agreements on aneurysm “depth,” “length,” “aneurysm plus parent artery,” and “parent artery” for CTA and DSA were excellent (ICC > 0.75). Intra-rater agreement as to aneurysm “shape” was substantial to almost perfect (κ > 0.60). The CAVIS method of traumatic aneurysm characterization has remarkable inter- and intra-rater reliability and will facilitate further studies of the natural history and management of extracranial cerebrovascular traumatic aneurysms.

Abstract T P52: Technique for Measurement of Traumatic Aneurysms of the Cervical Internal Carotid Artery and Assessment of Reproducibility

Background: Traumatic aneurysms occur in 10-20% of blunt traumatic extracranial carotid artery injuries. There is currently no standardized method for characterization of traumatic aneurysms. This study presents a systematic method for aneurysm characterization on both digital subtraction angiography (DSA) and CT angiography (CTA). Methods: Four raters, including one vascular neurosurgeon, one neuroradiologist, and two senior neurosurgical residents independently reviewed 15 CTAs and 13 DSAs obtained at the time of diagnosis of the traumatic aneurysm. Raters were asked to categorize the aneurysms as either ‘saccular’ or ‘fusiform’ and obtain measurements. Saccular aneurysm size was defined as the greatest linear distance between the expected location of the normal artery wall and the outer edge of the aneurysm lumen (‘depth’). Fusiform aneurysm size was defined as the depth and longitudinal extent (‘length’) parallel to the normal artery. The size of the aneurysm (‘aneurysm plus parent artery’) in relationship to the normal artery (‘parent artery’) was assessed as well. Assessments of five scans of each imaging modality were repeated for measurement of intra-rater reliability. Fleiss's free-marginal multi-rater kappa (κ), Cohen’s kappa (κ), and interclass correlation coefficient (ICC) were applied to determine inter- and intra-rater reliability. Results: Inter-rater agreement on aneurysm shape, ‘saccular’ versus ‘fusiform’, was almost perfect for CTA (κ = 0.82) and DSA (κ = 0.897). Agreement on aneurysm ‘depth’, ‘length’, ‘aneurysm plus parent artery’, and ‘parent artery’ for CTA and DSA were excellent (ICC > 0.75). Intra-rater agreement on aneurysm shape was substantial to almost perfect (κ > 0.6) in all four raters. Conclusions: This study demonstrates a clinically oriented, standardized method to characterize traumatic aneurysms with remarkable inter- and intra-rater reliability. This approach may help to define this disease entity more clearly and better understand the natural history. While certain characteristics of traumatic aneurysms may be associated with low risk and treatment with antithrombotic therapy may be sufficient, other characteristics may carry increased risk warranting endovascular repair.

Mathematical Analysis of Non-Newtonian Blood Flow in Stenosis Narrow Arteries

The flow of blood in narrow arteries with bell-shaped mild stenosis is investigated that treats blood as non-Newtonian fluid by using the K-L model. When skin friction and resistance of blood flow are normalized with respect to non-Newtonian blood in normal artery, the results present the effect of stenosis length. When skin friction and resistance of blood flow are normalized with respect to Newtonian blood in stenosis artery, the results present the effect of non-Newtonian blood. The effect of stenosis length and effect of non-Newtonian fluid on skin friction are consistent with the Casson model in which the skin friction increases with the increase of ither stenosis length or the yield stress but the skin friction decreases with the increase of plasma viscosity coefficient. The effect of stenosis length and effect of non-Newtonian fluid on resistance of blood flow are contradictory. The resistance of blood flow (when normalized by non-Newtonian blood in normal artery) increases when either the plasma viscosity coefficient or the yield stress increases, but it decreases with the increase of stenosis length. The resistance of blood flow (when normalized by Newtonian blood in stenosis artery) decreases when either the plasma viscosity coefficient or the yield stress increases, but it decreases with the increase of stenosis length.

Mathematical Analysis of Casson Fluid Model for Blood Rheology in Stenosed Narrow Arteries

The flow of blood through a narrow artery with bell-shaped stenosis is investigated, treating blood as Casson fluid. Present results are compared with the results of the Herschel-Bulkley fluid model obtained by Misra and Shit (2006) for the same geometry. Resistance to flow and skin friction are normalized in two different ways such as (i) with respect to the same non-Newtonian fluid in a normal artery which gives the effect of a stenosis and (ii) with respect to the Newtonian fluid in the stenosed artery which spells out the non-Newtonian effects of the fluid. It is found that the resistance to flow and skin friction increase with the increase of maximum depth of the stenosis, but these flow quantities (when normalized with non-Newtonian fluid in normal artery) decrease with the increase of the yield stress, as obtained by Misra and Shit (2006). It is also noticed that the resistance to flow and skin friction increase (when normalized with Newtonian fluid in stenosed artery) with the increase of the yield stress.