The Effect of Head Rotation on the Geometry and Hemodynamics of Healthy Vertebral Arteries

Aristokleous, Nicolas; Seimenis, Ioannis; Georgiou, Georgios C.; Nicolaides, Andrew

doi:10.1007/s10439-015-1340-5

Cited by 12 publications

(8 citation statements)

References 35 publications

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“…Previous studies suggest that neck movement can significantly alter vascular morphology in a patient specific fashion. 4 , 5 It is therefore possible that the morphology of an AVF changes when a patient moves or bends their arm. Finally, future work should development both bench-top and in-vivo pre-clinical experiments, in order to validate the computational results.…”

Section: Discussionmentioning

confidence: 99%

The Effect of Arterial Curvature on Blood Flow in Arterio-Venous Fistulae: Realistic Geometries and Pulsatile Flow

Grechy

Iori

Corbett

et al. 2017

Cardiovasc Eng Tech

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Arterio-Venous Fistulae (AVF) are regarded as the “gold standard” method of vascular access for patients with End-Stage Renal Disease (ESRD) who require haemodialysis. However, up to 60% of AVF do not mature, and hence fail, as a result of Intimal Hyperplasia (IH). Unphysiological flow and oxygen transport patterns, associated with the unnatural and often complex geometries of AVF, are believed to be implicated in the development of IH. Previous studies have investigated the effect of arterial curvature on blood flow in AVF using idealized planar AVF configurations and non-pulsatile inflow conditions. The present study takes an important step forwards by extending this work to more realistic non-planar brachiocephalic AVF configurations with pulsatile inflow conditions. Results show that forming an AVF by connecting a vein onto the outer curvature of an arterial bend does not, necessarily, suppress unsteady flow in the artery. This finding is converse to results from a previous more idealized study. However, results also show that forming an AVF by connecting a vein onto the inner curvature of an arterial bend can suppress exposure to regions of low wall shear stress and hypoxia in the artery. This finding is in agreement with results from a previous more idealized study. Finally, results show that forming an AVF by connecting a vein onto the inner curvature of an arterial bend can significantly reduce exposure to high WSS in the vein. The results are important, as they demonstrate that in realistic scenarios arterial curvature can be leveraged to reduce exposure to excessively low/high levels of WSS and regions of hypoxia in AVF. This may in turn reduce rates of IH and hence AVF failure.

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Section: Discussionmentioning

confidence: 99%

The Effect of Arterial Curvature on Blood Flow in Arterio-Venous Fistulae: Realistic Geometries and Pulsatile Flow

Grechy

Iori

Corbett

et al. 2017

Cardiovasc Eng Tech

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“…The image‐based computational modelling methodology employed in the present work, from MR images to CFD simulations allows estimating hemodynamic parameters based on wall shear stress (WSS) metrics, which have been found to be important in the development of thrombosis arising from IH . The accuracy of CFD predictions was investigated by Steinman et al and concluded that the pressure drop was reasonably well predicted …”

Section: Methodsmentioning

confidence: 99%

“…More specifically, Glor et al have first reported that head rotation may cause geometric changes to the right carotid bifurcation with leftward rotation of the head. 11 Then, other researchers cited alterations due to posture changes to the popliteal artery, 12 vertebral arteries, 13 and right and left carotid bifurcation. 14 The objective of this study was therefore to present a methodology to calculate geometric and hemodynamic parameters in healthy arm vessels, and to find their range of variation in two investigated positions.…”

mentioning

confidence: 99%

Morphological and hemodynamical alterations in brachial artery and cephalic vein. An image‐based study for preoperative assessment for vascular access creation

Aristokleous

Houston

Browne

et al. 2018

Numer Methods Biomed Eng

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The current study aims to computationally evaluate the effect of right upper arm position on the geometric and hemodynamic characteristics of the brachial artery (BA) and cephalic vein (CV) and, furthermore, to present in detail the methodology to characterise morphological and hemodynamical healthy vessels. Ten healthy volunteers were analysed in two configurations, the supine (S) and the prone (P) position. Lumen 3D surface models were constructed from images acquired from a non-contrast MRI sequence. Then, the models were used to numerically compute the physiological range of geometric (n = 10) and hemodynamic (n = 3) parameters in the BA and CV. Geometric parameters such as curvature and tortuosity, and hemodynamic parameters based on wall shear stress (WSS) metrics were calculated with the use of computational fluid dynamics. Our results highlight that changes in arm position had a greater impact on WSS metrics of the BA by altering the mean and maximum blood flow rate of the vessel. Whereas, curvature and tortuosity were found not to be significantly different between positions. Inter-variability was associated with antegrade and retrograde flow in BA, and antegrade flow in CV. Shear stress was low and oscillatory shear forces were negligible. This data suggests that deviations from this state may contribute to the risk of accelerated intimal hyperplasia of the vein in arteriovenous fistulas. Therefore, preoperative conditions coupled with post-operative longitudinal data will aid the identification of such relationships.

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“…Extensive use of MRI for the generation of geometries for computational modelling and image-based computational fluid dynamics (CFD) can be found in biomedical engineering area, and the generation of geometries from MR images is well established. 7 , 8 , 28 A brief overview of the progress achieved in the field of image-based CFD studies was done by Steinman and Taylor 79 , 85 with applications in research assessing WSS-based metrics. 78 …”

Section: Mrimentioning

confidence: 99%

Imaging in Vascular Access

Murphy

Ross

Jones

et al. 2017

Cardiovasc Eng Tech

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This review examines four imaging modalities; ultrasound (US), digital subtraction angiography (DSA), magnetic resonance imaging (MRI) and computed tomography (CT), that have common or potential applications in vascular access (VA). The four modalities are reviewed under their primary uses, techniques, advantages and disadvantages, and future directions that are specific to VA. Currently, US is the most commonly used modality in VA because it is cheaper (relative to other modalities), accessible, non-ionising, and does not require the use of contrast agents. DSA is predominantly only performed when an intervention is indicated. MRI is limited by its cost and the time required for image acquisition that mainly confines it to the realm of research where high resolution is required. CT’s short acquisition times and high resolution make it useful as a problem-solving tool in complex cases, although accessibility can be an issue. All four imaging modalities have advantages and disadvantages that limit their use in this particular patient cohort. Current imaging in VA comprises an integrated approach with each modality providing particular uses dependent on their capabilities. MRI and CT, which currently have limited use, may have increasingly important future roles in complex cases where detailed analysis is required.

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The Effect of Head Rotation on the Geometry and Hemodynamics of Healthy Vertebral Arteries

Cited by 12 publications

References 35 publications

The Effect of Arterial Curvature on Blood Flow in Arterio-Venous Fistulae: Realistic Geometries and Pulsatile Flow

The Effect of Arterial Curvature on Blood Flow in Arterio-Venous Fistulae: Realistic Geometries and Pulsatile Flow

Morphological and hemodynamical alterations in brachial artery and cephalic vein. An image‐based study for preoperative assessment for vascular access creation

Imaging in Vascular Access

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