CT-based multi-threshold calcium scoring for aortic valve assessment: comparable predictive performance across HU thresholds in a pre-TAVI cohort

To determine whether higher Hounsfield unit (HU) thresholds for computed tomography-derived aortic valve calcium (CT-AVC) scoring provide additional hemodynamic or discriminatory value beyond conventional 130-HU Agatston scoring in classical high-flow/high-gradient severe aortic stenosis (AS). This single-center retrospective cohort included 63 consecutive pre-TAVI patients with trileaflet, classical high-flow/high-gradient severe AS. CT-AVC was quantified on non-contrast ECG-gated CT at 130, 200, 500, 800, and 1000 HU within a manually defined leaflet/annulus region of interest, excluding left ventricular outflow tract and mitral annular calcification. Associations with peak gradient, mean gradient, and aortic valve area were assessed using correlation and multivariable linear regression.Exploratory ROC analysis assessed discrimination of very severe hemodynamic burden, defined as a mean gradient ≥ 60 mmHg, within the established severe-AS cohort, with ROC areas compared using DeLong testing. CT-AVC at all HU thresholds was independently associated with higher peak gradient (β, 0.010 at 130 HU to 0.144 at 1000 HU; all P ≤ 0.005) and higher mean gradient (β, 0.0059 at 130 HU to 0.073 at 1000 HU; all P ≤ 0.024). Associations with aortic valve area were not statistically significant. Within-cohort discrimination of very severe hemodynamic burden was modest and comparable across thresholds (AUC 0.65-0.67), with no statistically significant difference by DeLong testing (P = 0.68). In classical high-flow/high-gradient severe AS, CT-AVC demonstrated consistent associations with transvalvular gradients across HU thresholds. Higher HU thresholds did not outperform conventional 130-HU scoring and showed only modest, comparable performance for within-severity hemodynamic stratification. These thresholds should be interpreted as complementary densitometric analyses rather than alternative diagnostic cut-offs.