In vivo validation of mathematically derived fractional flow reserve for assessing haemodynamics of coronary tandem lesions.

Abstract

Our aim was to propose a prediction model for the post-stenting fractional flow reserve (FFR'd,pred) at a position distal to the tandem lesion. Using the FFR at a position proximal to the tandem lesion (FFRp), and the FFR gradients across proximal (ΔFFRp) and distal (ΔFFRd) stenoses, FFR'd,pred after treating either the distal or proximal lesion was predicted as FFRp-ΔFFRp/(1-1.33kΔFFRd) or FFRp-ΔFFRd/(1-1.33ΔFFRp), respectively. The flow fraction of the distal main branch (k) was estimated using the diameter ratio of side to distal main branches. For in vivo validation, 50 patients with a tandem lesion (diameter stenosis >50%) were evaluated. Compared to the conventional model that did not consider side branch flow, our predicted FFR showed closer correlation with the measured FFR (R2=0.83 vs. 0.57) and significant reduction in mean absolute errors (0.034±0.028 vs. 0.053±0.049, p<0.001). In particular, with a large side branch and low baseline FFR, decision making using the current model had greater predictive ability than with the conventional model. By predicting which stenosis is more severe and/or whether the remaining lesion after the first treatment is functionally significant, a tandem prediction model can help to plan optimised stent implantation.