Influence of Collaterals on True FFR Prediction for a Left Main Stenosis with Concomitant Lesions: An In Vitro Study

With the aim of assisting interventional cardiologists during decision making for revascularization, reduced-order (0D) approaches have been developed to predict the true fractional flow reserve (FFR_True) of individual stenoses in multiple-lesion arrangements. In this study, a general equation was derived to predict the FFR_True of a left main (LM) coronary stenosis with downstream lesions, one in the left anterior descending (LAD) and the other in the left circumflex (LCx) artery, and distinct collateral circulations supplying each daughter artery. An in vitro model mimicking the fractal nature of LM bifurcation trees with collateral branches was developed to validate the FFR values obtained with the prediction model (FFR _Pred ^Model ). Our results demonstrated that: (1) considering collaterals significantly improved the FFR _Pred ^Model estimation for a moderate LM stenosis with two downstream lesions as compared to computations with no collateral consideration (p < 0.001): mean absolute error |FFR _Pred ^Model  - FFR_True| ± SD was equal to 0.02 ± 0.01 vs. 0.04 ± 0.02 respectively, and (2) Deviations from FFR_True for LM stenoses are correlated to both, downstream lesion severities and collateral developments. The present study supports the hypothesis that collateral circulations supplying the LAD and LCx must be considered when predicting the FFR_True of an LM stenosis with downstream lesions.