Topological manifold versus multidirectional wall shear stress FSI approaches for the right coronary artery

To date, researchers in the field of biomechanics have used various wall shear stress-based parameters to analyse hemodynamics to improve the medical understanding of atherosclerosis. In this paper, we aim to provide a comprehensive comparison between commonly used multidirectional and topological skeleton variables for a complex, patient-specific model of the right coronary artery (RCA) via a two-phase fluid-structure interaction (FSI) technique. To better replicate the real physiological conditions, a two-phase blood flow, comprising plasma and red blood cells, is considered. Additionally, a hyperelastic behaviour is defined for the RCA structure to represent the mechanical properties of human coronary arteries. Boundary conditions, including the velocity of blood components at the inlet and arterial wall motion, are configured based on in vivo data available in the literature. To identify regions prone to atherosclerosis and assess arterial vulnerability, recent studies have primarily focused on multidirectional wall shear stress (WSS) parameters. However, comparatively little attention has been given to topological hemodynamic features. In this work, we first derived the time averaged wall shear stress (TAWSS) and oscillatory shear index (OSI) as representatives of the multidirectional WSS, and WSS divergence and fixed points as representatives of the topological hemodynamics, and analysed them to evaluate arterial vulnerability. Among the main findings, this study shows that although both multidirectional and topology-skeleton metrics co-localise vulnerable regions of the artery, WSS divergence, as a topology-skeleton index, identifies these areas in a fragmented and localised manner. This represents a step toward defining more precise vulnerable zones in the cardiovascular system and predicting high-risk regions with greater accuracy.