Sex-Specific Variances in Anatomy and Blood Flow of the Left Main Coronary Bifurcation: Implications for Coronary Artery Disease Risk

OBJECTIVE: Studies have shown marked sex disparities in Coronary Artery Diseases (CAD) epidemiology, yet the underlying mechanisms remain unclear. We explored the coronary anatomy and the resulting haemodynamics in patients with suspected but no significant CAD. Left Main (LM) bifurcations were 3D-reconstructed from 127 Computed Tomography Angiography images (42 males and 85 females, aged 38-81). METHODS: Shape parameters including bifurcation angles, curvature, and diameters were measured, before solving the clinically relevant haemodynamic metrics. The severity and location of the vascular area exposed to adverse haemodynamics were compared between sexes. RESULTS: Females were more likely than males to exhibit adversely low Time Averaged Endothelial Shear Stress (TAESS) 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 OSI (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: 4.0±0.5mm vs 3.3±0.6mm, LAD: 3.6±0.5mm vs 3.0±0.5mm, LCX:3.5±0.5mm vs 2.9±0.6mm), 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). There was no difference in bifurcation angles. CONCLUSION: These differences may in part contribute to differences in CAD risk between sexes. SIGNIFICANCE: This work facilitates a better understanding of sex differences in factors contributing to CAD, ultimately improving screening and therapeutic strategies particularly for women who currently have worse predictive outcomes.