Impact of coronary bifurcation angle on computed tomography derived fractional flow reserve in coronary vessels with no apparent coronary artery disease

Objectives Computed tomography (CT) derived fractional flow reserve (FFRCT) decreases from the proximal to the distal part due to a variety of factors. The energy loss due to the bifurcation angle may potentially contribute to a progressive decline in FFRCT. However, the association of the bifurcation angle with FFRCT is still not entirely understood. This study aimed to investigate the impact of various bifurcation angles on FFRCT decline below the clinically crucial relevance of 0.80 in vessels with no apparent coronary artery disease (CAD). Methods A total of 83 patients who underwent both CT angiography including FFRCT and invasive coronary angiography, exhibiting no apparent CAD were evaluated. Delta FFRCT was defined as the change in FFRCT from the proximal to the distal in the left anterior descending artery (LAD) and left circumflex artery (LCX). The bifurcation angle was calculated from three-dimensional volume rendered images. Vessel morphology and plaque characteristics were also assessed. Results Delta FFRCT significantly correlated with the bifurcation angle (LAD angle, r = 0.35, p = 0.001; LCX angle, r = 0.26, p = 0.02) and vessel length (LAD angle, r = 0.30, p = 0.005; LCX angle, r = 0.49, p < 0.0001). In LAD, vessel length was the strongest predictor for distal FFRCT of <= 0.80 (beta-coefficient = 0.55, p = 0.0003), immediately followed by the bifurcation angle (beta-coefficient = 0.24, p = 0.02). The bifurcation angle was a good predictor for a distal FFRCT <= 0.80 (LAD angle, cut-off 31.0 degrees, AUC 0.70, sensitivity 74%, specificity 68%; LCX angle, cut-off 52.6 degrees, AUC 0.86, sensitivity 88%, specificity 85%). Conclusions In vessels with no apparent CAD, vessel length was the most influential factor on FFRCT, directly followed by the bifurcation angle.