Effects of Fractional Flow Reserve on Coronary Artery Bypass Graft Flow to Left Anterior Descending Artery

Background: The relationships between preoperative fractional flow reserve (FFR) values of the left anterior descending artery (LAD), FFRLAD, and intraoperative transit time flow measurement (TTFM) variables in coronary artery bypass grafting (CABG) remain unclear. Methods and Results: We retrospectively collected data for 74 in situ left internal thoracic artery (LITA) grafts and 27 saphenous vein grafts (SVGs) to the LAD that were shown to be patent on postoperative angiography. Spearman correlation coefficients were determined between FFRLAD and TTFM parameters of the LITA graft, as follows: maximum flow (Qmax), −0.22 (P=0.077); minimum flow (Qmin), −0.40 (P=0.014); mean flow (Qm), −0.35 (P=0.039); pulsatility index (PI), 0.33 (P=0.008); diastolic filling (DF): 0.01 (P=0.83); and systolic reverse flow (SRF), 0.37 (P=0.002). Spearman correlation coefficients between FFRLAD and TTFM parameters of the SVG to LAD were: Qmax, −0.65 (P=0.004); Qmin, −0.43 (P=0.044); Qm, −0.75 (P=0.001); PI, 0.53 (P=0.033); DF, 0.14 (P=0.48); and SRF, 0.61 (P=0.009). Conclusions: Both LITA grafts and SVGs to the LAD show negative correlations for FFRLAD with Qmin and Qm, but positive correlations for FFRLAD with PI and SFR. These relationships between FFRLAD and TTFM variables of CABG grafts to the LAD should be recognized.