High-intensity helical flow: a double-edged sword in coronary artery haemodynamics

The role of helical flow in human coronary arteries remains uncertain, yet its understanding promises unprecedented insights into atherosclerotic processes. In this study, we investigated the effects of helical flow and key haemodynamic descriptors in 39 patient-specific left coronary artery trees of the Automated Segmentation of Coronary Arteries (ASOCA) dataset: 20 non-stenosed and 19 stenosed. Absolute helical flow intensity h ₂ correlated with higher time-averaged endothelial shear stress in all vessel segments regardless of stenoses ( $p<0.05$ ). In stenosed cases, this correlation was so prominent that the vessel area exposed to adversely low time-averaged endothelial shear stress reduced (less than 0.5 Pa $,p=0.0001$ ), and simultaneously, areas of adversely high time-averaged endothelial shear stress increased (greater than 4.71 Pa, $p<0.05$ ) coinciding with high h ₂ regions. This suggests that helical flow in coronaries is not always protective, as previously thought, because it not only mitigates low time-averaged endothelial shear stress associated with long-term plaque development and restenosis but also exacerbates adversely high time-averaged endothelial shear stress linked to increased plaque vulnerability and even acute events. Our findings redefined the current understanding of the role of helical blood flow in cardiovascular atherosclerotic disease processes.