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 (FFR(CT)) 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 FFR(CT). However, the association of the bifurcation angle with FFR(CT) is still not entirely understood. This study aimed to investigate the impact of various bifurcation angles on FFR(CT) 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 FFR(CT) and invasive coronary angiography, exhibiting no apparent CAD were evaluated. ΔFFR(CT) was defined as the change in FFR(CT) 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: ΔFFR(CT) 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 FFR(CT) of ≤ 0.80 (β-coefficient = 0.55, p = 0.0003), immediately followed by the bifurcation angle (β-coefficient = 0.24, p = 0.02). The bifurcation angle was a good predictor for a distal FFR(CT) ≤ 0.80 (LAD angle, cut-off 31.0°, AUC 0.70, sensitivity 74%, specificity 68%; LCX angle, cut-off 52.6°, AUC 0.86, sensitivity 88%, specificity 85%). CONCLUSIONS: In vessels with no apparent CAD, vessel length was the most influential factor on FFR(CT), directly followed by the bifurcation angle. KEY POINTS: • Both LAD and LCX bifurcation angles are factors influencing FFR (CT). • Bifurcation angle is one of the predictors of a distal FFR(CT) of ≤ 0.80 and an optimal cut-off value of 31.0° for the LAD and 52.6° for the LCX. • Bifurcation angle should be taken into consideration when interpreting numerical values of FFR (CT) . SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00330-022-09125-3.