SmartFFR, a New Functional Index of Coronary Stenosis: Comparison With Invasive FFR Data

Abstract

Aims: In this study, we evaluate the efficacy of SmartFFR, a new functional index of coronary stenosis severity compared with gold standard invasive measurement of fractional flow reserve (FFR). We also assess the influence of the type of simulation employed on smartFFR (i.e. Fluid Structure Interaction vs. rigid wall assumption).Methods and Results: In a dataset of 167 patients undergoing either computed tomography coronary angiography (CTCA) and invasive coronary angiography or only invasive coronary angiography (ICA), as well as invasive FFR measurement, SmartFFR was computed after the 3D reconstruction of the vessels of interest and the subsequent blood flow simulations. 202 vessels were analyzed with a mean total computational time of seven minutes. SmartFFR was used to process all models reconstructed by either method. The mean FFR value of the examined dataset was 0.846 ± 0.089 with 95% CI for the mean of 0.833–0.858, whereas the mean SmartFFR value was 0.853 ± 0.095 with 95% CI for the mean of 0.84–0.866. SmartFFR was significantly correlated with invasive FFR values (RCCTA = 0.86, pCCTA < 0.0001, RICA = 0.84, pICA < 0.0001, Roverall = 0.833, poverall < 0.0001), showing good agreement as depicted by the Bland-Altman method of analysis. The optimal SmartFFR threshold to diagnose ischemia was ≤0.83 for the overall dataset, ≤0.83 for the CTCA-derived dataset and ≤0.81 for the ICA-derived dataset, as defined by a ROC analysis (AUCoverall = 0.956, p < 0.001, AUCICA = 0.975, p < 0.001, AUCCCTA = 0.952, p < 0.001).Conclusion: SmartFFR is a fast and accurate on-site index of hemodynamic significance of coronary stenosis both at single coronary segment and at two or more branches level simultaneously, which can be applied to all CTCA or ICA sequences of acceptable quality.

A novel physics-based model for fast computation of blood flow in coronary arteries

“…For each patient, a constant mean aortic pressure of 100 mmHg was applied to model the inlet pressure of a coronary artery at rest [ 33 – 35 ]. Thus, the hyperemic aortic pressure that was used to estimate FFR turned to 90 mmHg.…”

“…The previous study showed that the impact of prescribed inlet pressure, including pressure measured non-invasively, pressure acquired during invasive FFR measurement, and a fixed value of 100 mmHg, on FFR prediction frameworks is of little importance [ 34 ]. In the other two studies regarding the virtual functional assessment of coronary stenosis, a mean aortic pressure of 100 mmHg was also imposed at the inlet of coronary artery for CFD calculations [ 33 , 35 ]. As a result, both virtual hemodynamic assessment models showed high diagnostic performance in detecting lesion-specific ischemia using invasive FFR as a reference standard.…”

An All-in-One Tool for 2D Atherosclerotic Disease Assessment and 3D Coronary Artery Reconstruction

“…Future steps in the development include further evaluating its performance by installing it into more clinical centers. Moreover, as performed previously with other tools of our lab, the reconstructed results will be used as input to other tools such as the SmartFFR calculation [ 27 ], the prediction of atherosclerotic plaque growth, or the simulation of stent deployment.…”

Error Propagation in the Simulation of Atherosclerotic Plaque Growth and the Prediction of Atherosclerotic Disease Progression

“…SmartFFR [ 13 , 14 ], which is a computational approach to estimate invasive FFR, was calculated based on a transient simulation of blood flow (consisting of 5 timesteps with timestep duration 0.25 s), applying an average pressure 100 mmHg at the inlet (i.e., mean human aortic pressure) and, at the outlet, a volumetric flow rate 0, 1, 2, 3 and 4 mL/s was applied per timestep. No-slip and no-penetration boundary conditions were used at the endothelial membrane boundary.…”