Effect of side branch flow upon physiological indices in coronary artery disease

Rebecca C Gosling,Jacob Sturdy,Paul D Morris,Fredrik Eikeland Fossan,Leif Rune Hellevik,Patricia Lawford,D Rodney Hose,Julian Gunn

doi:10.1016/j.jbiomech.2020.109698

Abstract

Recent efforts have demonstrated the ability of computational models to predict fractional flow reserve from coronary artery imaging without the need for invasive instrumentation. However, these models include only larger coronary arteries as smaller side branches cannot be resolved and are therefore neglected. The goal of this study was to evaluate the impact of neglecting the flow to these side branches when computing angiography-derived fractional flow reserve (vFFR) and indices of volumetric coronary artery blood flow. To compensate for the flow to side branches, a leakage function based upon vessel taper (Murray’s Law) was added to a previously developed computational model of coronary blood flow. The augmented model with a leakage function (1Dleaky) and the original model (1D) were then applied to predict FFR as well as inlet and outlet flow in 146 arteries from 80 patients who underwent invasive coronary angiography and FFR measurement. The results show that the leakage function did not significantly change the vFFR but did significantly impact the estimated volumetric flow rate and predicted coronary flow reserve. As both procedures achieved similar predictive accuracy of vFFR despite large differences in coronary blood flow, these results suggest careful consideration of the application of this index for quantitatively assessing flow.

Highlights

Fractional flow reserve (FFR) is the gold standard method to evaluate the physiological significance of epicardial coronary artery disease (CAD) (Neumann et al, 2018)
Vardhan et al (2019) demonstrated that neglecting side branches increased estimates of wall shear stresses in coronary trees of 21 patients by comparing Three dimensional (3D) computational fluid dynamics (CFD) of geometries reconstructed from biplane angiography images and including all, some and no side branches. These previous studies all found significant changes in pressure drops when imposing fixed inflow conditions on models accounting for varying numbers of branches. The difference between these results and the marginal change we found in virtual fractional flow reserve (vFFR) of the One dimensional with leakage term (1Dleaky) model (0.005) is due to differences in the imposed boundary conditions
The accuracy of computational models of FFR depends on the anatomical and physiological assumptions which are made during the computational process

Summary

Introduction

Fractional flow reserve (FFR) is the gold standard method to evaluate the physiological significance of epicardial coronary artery disease (CAD) (Neumann et al, 2018). Accuracy is limited by various anatomical and physiological assumptions made to enable computational modelling (Eck et al, 2016; Fossan et al, 2018; Morris et al, 2017; Sankaran et al, 2016; Sturdy et al, 2019). Prior work often assumes the flow to side branches is non-influential and models the artery of interest as a single lumen (Morris et al, 2013).

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