Arterial fluid mechanics and their influence on cardiovascular disease

Despite mortality trends within the European Union declining throughout the last century; Cardiovascular Diseases (CVDs) are becoming increasing prevalent contributing to approximately 31% of all global deaths (1, 2). Extensive research into the diagnosis, prevention and treatment of CVD is needed to reduce this statistic.
If arterial geometry and biofluid mechanics could be used to evaluate risk of CVD, intervention could be carried out at an earlier stage before symptoms appear. Research suggests that atherosclerosis formation (accumulation of fatty deposits over time, decreasing arterial diameter) tends to occur near to vessel bifurcations and through curved arterial segments because of 'disturbed' flow (3). A stent is an expandable scaffold mesh that is placed in a narrowed arterial region to increase vessel diameter and reduce blood flow disruption through the arterial segment (4, 5). Whilst the design of stents is constantly evolving to help reduce vessel damage, disruption of arterial fluid mechanics and the likelihood of a recurrent atherosclerotic blockage; understanding the initial cause of flow disruption, could help to pioneer new treatments with even fewer complications (6, 7).

Particle Image Velocimetry (PIV) uses laser optics and digital imaging techniques to visualise fluid flow (8, 9). The fluid is 'seeded' with miniscule particles that are considered neutrally buoyant; thus, these particles follow the flow dynamics of the fluid. The motion of these particles can be obtained by passing a light through the fluid and comparing multiple photographs obtained at a high frequency. PIV can be used to explore turbulence on aerofoils or evaluate fluid flow through a vessel.
The proposed project will utilise PIV techniques to determine the instantaneous velocity of a fluid in an arterial model using a flow 'phantom'. Multiple models will be explored to determine how much influence arterial geometry has on CVD risk. The fluid will be exposed to pulsatile motion mimicking observations during the cardiac cycle. Initially rigid arterial models may be assumed with more physiologically realistic (compliant) models being evaluated at a later stage. Fabrication of the arterial models may involve 3D printing methods or investment casting techniques, developed using Computer Aided Design.
While the initial aim of the project is to explore the influence arterial geometry has of CVD risk, the experimental setup may be further developed to aid as a testbed for the evolution of new surgical devices, helping to increase global life expectancy.
The project will be progressed iteratively, beginning with simple geometries and flow parameters before increasing in complexity to consider more realistic physiological conditions. The experiments will also be complimented with Computational Fluid Dynamics simulations to support findings.
References
1. European Commission, Health statistics - Atlas on mortality in the European Union. (2009).
2. WHO. (World Health Organization, 2017), vol. 2021.
3. C. S. Coradi et al., in Vascular Diseases for the Non-Specialist: An Evidence-Based Guide, T. P. Navarro, A. Dardik, D. Junqueira, L. Cisneros, Eds. (Springer International Publishing, Cham, 2017), pp. 35-45.s
4. BHF. (British Heart Foundation, 2019), vol. 2021.
5. NHS. (NHS, 2018), vol. 2021.
6. S. Beier et al., Hemodynamics in Idealized Stented Coronary Arteries: Important Stent Design Considerations. Annals of Biomedical Engineering: The Journal of the Biomedical Engineering Society 44, 315 (2016).
7. R. L. Noad, C. G. Hanratty, S. J. Walsh, Clinical Impact of Stent Design. Interventional Cardiology Review 9, 89-93 (2014).
8. I. Grant, Particle image velocimetry: A review. Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 211, 55-76 (1997).
9. J. Grue, P. L. F. Liu, G. K. Pedersen, Piv And Water Waves. (World Scientific Publishing Company, Singapore, 2004).