Simulation of Blood Flow in Arteries for Functional Assessment of Coronary Disease: Implementation of Numerical Code

Resumo

Cardiovascular diseases are a major cause of mortality and morbidity in developed countries. Coronary atherosclerotic disease (CAD) is a degenerative process that is characterized by the development of atheromatous plaques on the wall of coronary arteries. Clinical manifestations of CAD range from stable angina, resulting from progressive plaque growth with partial obstruction of the arterial lumen (stenosis) and consequent limitation of coronary blood flow. In clinical practice, a diagnostic strategy is widely used to assess the functional relevance of CAD: the invasive assessment of myocardial fractional flow reserve (FFR).
Coronary Computed Tomography Angiography (CTA) is an established non-invasive diagnostic tool for evaluating CAD. However, CTA can overestimate anatomic stenosis and is limited in that it does not provide information on the hemodynamic relevance of coronary stenosis. Thus, the implementation and numerical simulation of blood flow in arteries in the most real physiological conditions has been one of the main areas of interest of the authors [1]. The main purpose of this work is to develop and validate a computational tool for calculating the FFR and hemodynamic descriptors.
In this way, to obtain the most accurate non-invasive FFR, the hemodynamic numerical tool was hardly improved to establish real conditions, specific to each patient case with CAD. Therefore, to achieve accurate pressures, Windkessel models, mainly based on the resistance of blood flow [2], were implemented considering hyperemia conditions (maximal dilation of the coronary tree), since the patient must be subjected to this condition during the catheterization to obtain the invasive FFR (reference value for validation). Moreover, the 3D patient-specific geometry of the artery was modified to simulate blood flow in hyperemic conditions. The numerical code development was performed in ANSYS® software.
After validation, the authors aim to create a software for local use, allowing a comprehensive assessment of CAD in an accessible, fast, reliable, and non-invasive way.

[1] Pinto, S.I.S. et al. (2020). The impact of non-linear viscoelastic property of blood in right coronary arteries hemodynamics a numerical implementation. International Journal of Non-Linear Mechanics 123, 103477.
[2] Boileau, E. et al. (2018) Estimating the accuracy of a reduced-order model for calculation of fractional flow reverse (FFR). Int J Numer Meth Biomed Engng 34, e2908.