Coronary flow disturbance assessed by vorticity as a cause of functionally significant stenosis

Abstract

Objectives: Vorticity calculated using computational fluid dynamics (CFD) could assess the flow disturbance generated by coronary stenosis. The purpose of this study was to investigate whether vorticity would be an underlying cause of functionally significant stenosis assessed by invasive fractional flow reserve (FFR).

Methods: This retrospective study included 113 patients who underwent coronary CT angiography showing intermediate stenosis and subsequent invasive FFR between December 2015 and March 2020. Vorticity at the stenosis site was calculated using a mesh-free CFD method. We also evaluated the minimum lumen area (MLA) and diameter stenosis (DS) of the lesion. Invasive FFR of ≤ 0.80 was considered functionally significant. Data were compared using Student's t-test and logistic regression analysis was performed.

Results: Of the evaluated 144 vessels, 53 vessels (37%) showed FFR ≤ 0.80. Vorticity of significant stenosis was significantly higher than non-significant stenosis (569 ± 78 vs. 328 ± 34 s^-1, p < 0.001). A significant negative relationship was present between vorticity and invasive FFR (R² = 0.31, p < 0.001). Multivariate logistic regression analysis including MLA and DS showed that vorticity (per 100 s^-1, odds ratio: 1.36, 95% confidence interval: 1.21-1.57, p < 0.001) was a statistically significant factor to detect functional significance. The area under the receiver operating characteristic curve statistically significantly increased when vorticity was combined with DS and MLA (0.76 vs. 0.87, p = 0.001).

Conclusions: Vorticity had a statistically significant negative relationship with invasive FFR independent of geometric stenosis.

Key points: • Flow disturbance caused by coronary stenosis could be evaluated by calculating vorticity which is defined as the norm of the rotation of the velocity vector. • Vorticity was statistically significantly higher in stenosis with functional significance than stenosis without. • Vorticity has an additive value to detect functionally significant stenosis over geometrical stenosis.

Keywords: CT angiography; Computational modeling; Coronary artery stenosis.