A Novel Physiologically Based Algorithm (PBA) for Fast CFD Computation of Flow Fractional Reserve (FFR) in Coronary Artery Trees

Abstract

A novel physiologically based algorithm (PBA) for fast CFD computation of Flow Fractional Reserve (FFR) in Coronary Artery Trees (CATs) is proposed and developed, which, unlike traditional methods, is based on the extension of the Murray’s law for blood vessels at the outlets and extra inlet conditions prescribed alternatively and iteratively. The PBA is then implemented in both SimVascular and Ansys CFD for testing and validation. For validation purpose, 3D models of CATs are built by using their CT images and computational meshes generated for mesh convergence study. Results obtained are then compared with Invasive Coronary Angiographic (ICA) data for validation and evaluation of its accuracy and computational efficiency. It is found that discrepancies between experimental and calculated values of pressure and flow rate at the inlet were less than 0.1% at the end of the 10th round of iteration or less. Further validation shows that the difference between estimated and experimental FFR agree with each other with a maximum difference of 1.62% after convergence is achieved. The PBA is found to be a robust patient-specific and physiologically sound method that can be a good alternative to the existing Lumped Parameter Model (LPM) which is based on empirical scaling correlations using limited population-averaged data and requires nonlinear iterative computation for convergence.

CFD Computation of Flow Fractional Reserve (FFR) in Coronary Artery Trees Using a Novel Physiologically Based Algorithm (PBA) Under 3D Steady and Pulsatile Flow Conditions

“…The calculated noninvasive FFR value of 0.73 by Zhang et al [ 23 ] is different from the experimental (ICA) FFR value of approximately 0.76 for the CT209 model. After conducting a mesh sensitivity analysis, Sumbekova et al [ 19 ] from our research group obtained a final FFR value of FFR = 0.757, which was very close to the ICA FFR. The same algorithm implemented in OpenFOAM produced results that were similar to the ICA measurement, with a final FFR value of FFR = 0.762.…”

“…cfMesh is also able to automatically generate tetrahedral meshes for a variety of geometries, as shown in Figure 9 . A mesh sensitivity analysis was conducted [ 19 ], and the same models were used in this study. For the CT209, CHN13, and CHN03 arteries, our research group [ 19 ] calculated mesh sizes and numbers of grid cells based on the results of the mesh sensitivity analysis.…”

“…We compared the steady-state results obtained by the PBA method in OpenFOAM with those obtained using a traditional lumped parameter method and the current approach used by our research group [ 19 ], as well as with the ICA measurement results. It was found that the PBA method demonstrated good accuracy and efficiency, similar to the traditional methods.…”

“…Three artery models were analyzed using both methods: the standard LPM technique was used in ANSYS [ 23 ], while the suggested PBA was implemented in Simvascular [ 19 ] and OpenFOAM for steady-state and transient cases, respectively, as described in Appendix A and Appendix B . Additionally, all abbreviations in this work are provided in Appendix C .…”

“…Table 9 provides a summary of the comparison between the computed and experimental ICA FFRs [ 19 ]. This table shows that the recommended PBA produced results that were independent of the solver.…”