Influence of pressure guidewire on coronary hemodynamics and fractional flow reserve

Invasive measurement of coronary fractional flow reserve (FFR) routinely involves the use of a pressure guidewire that will induce hemodynamic changes, thereby causing the measured FFR to deviate from the intact in vivo one. However, computational models used for predicting FFR often ignore the encroachment of vascular lumen by guidewire, which may compromise the comparability of model predictions with in vivo measurements. In this study, a geometrical multiscale model was developed to quantify the influences of two types of pressure guidewire (i.e., pressure wire and pressure catheter) on coronary hemodynamics and FFR. Numerical experiments were conducted on 35 idealized and 10 realistic models of the left anterior descending artery (LAD). Obtained results revealed that inserting a pressure guidewire into the LAD augmented the viscous pressure loss across the stenosis segment, leading to a decrease in blood flow rate, increase in trans-stenosis pressure drop, and consequently decrease in FFR. The guidewire-induced decrease in FFR was affected mainly by vascular diameter, stenosis rate, the number of stenosis, and the diameter of guidewire. More importantly, the study demonstrated the existence of a linear relationship between guidewire-present FFRs and guidewire-absent (intact) FFRs despite the large variations in stenosis rate and vascular morpho-geometrical characteristics, which could be explained by a theoretical model. These findings may serve as theoretical references for explaining or correcting the discrepancies between FFRs predicted by guidewire-absent models and in vivo measurements or converting invasively measured FFRs into the intact ones to better assess the functional impact of coronary artery stenoses.