  Studies have shown marked sex disparities in Coronary Artery Diseases (CAD)
epidemiology, yet the underlying mechanisms remain unclear. We explored sex
disparities in the coronary anatomy and the resulting haemodynamics in patients
with suspected, but no significant CAD. Left Main (LM) bifurcations were
reconstructed from CTCA images of 127 cases (42 males and 85 females, aged 38
to 81). Detailed shape parameters were measured for comparison, including
bifurcation angles, curvature, and diameters, before solving the haemodynamic
metrics using CFD. The severity and location of the normalised vascular area
exposed to physiologically adverse haemodynamics were statistically compared
between sexes for all branches. We found significant differences between sexes
in potentially adverse haemodynamics. Females were more likely than males to
exhibit adversely low Time Averaged Endothelial Shear Stress along the inner
wall of a bifurcation (16.8% vs. 10.7%). Males had a higher percentage of areas
exposed to both adversely high Relative Residence Time (6.1% vs 4.2%, p=0.001)
and high Oscillatory Shear Index (4.6% vs 2.3%, p<0.001). However, the OSI
values were generally small and should be interpreted cautiously. Males had
larger arteries (M vs F, LM: 4.0mm vs 3.3mm, LAD: 3.6mm 3.0mm, LCX:3.5mm vs
2.9mm), and females exhibited higher curvatures in all three branches (M vs F,
LM: 0.40 vs 0.46, LAD: 0.45 vs 0.51, LCx: 0.47 vs 0.55, p<0.001) and larger
inflow angle of the LM trunk (M: 12.9{\deg} vs F: 18.5{\deg}, p=0.025).
Haemodynamic differences were found between male and female patients, which may
contribute, at least in part, to differences in CAD risk. This work may
facilitate a better understanding of sex differences in the clinical
presentation of CAD, contributing to improved sex-specific screening,
especially relevant for women with CAD who currently have worse predictive
outcomes.
