Preliminary Experience in Quantifying Aortic Valve Calcification Using ECG-Gated Multislice Spiral Computed Tomography: Correlation with Hemodynamic Severity of Aortic Stenosis and Evolution to Modern Clinical Applications

Abstract: Objective: Degenerative calcific aortic stenosis (AS) is the most prevalent valvular heart disease in the elderly population. Earlier studies using electron-beam computed tomography (EBCT) demonstrated high reproducibility in quantifying aortic valve calcification (AVC). This preliminary investigation aimed to evaluate the feasibility of retrospectively ECG-gated multislice spiral computed tomography (MSCT) — an emerging technology at the time — for assessing AVC, and to correlate the degree of calcification with invasive hemodynamic parameters of AS severity obtained via cardiac catheterization, laying the groundwork for non-invasive evaluation. Methods: In this prospective study, 41 consecutive patients (18 men; mean age 71 ± 8 years) with varying degrees of AS underwent ECG-gated 4-detector row MSCT (retrospective gating) and subsequent invasive cardiac catheterization within a short interval. AVC was quantified using three established scoring methods: the Agatston score (adapted for the aortic valve), calcium mass score, and volumetric score. AS severity was graded hemodynamically by aortic valve area (AVA), peak-to-peak gradient, and mean transvalvular gradient from catheterization data. Correlations between AVC scores and hemodynamic parameters were analyzed. Results: Patients with severe AS (n=29) exhibited significantly higher AVC scores compared to those with moderate (n=7) or mild (n=5) AS (p<0.001). Significant inverse correlations were found between AVC scores and AVA (e.g., r = -0.49, p=0.001 for calcium mass score), alongside positive correlations with peak-to-peak (r = 0.68, p<0.001) and mean transvalvular gradients (r = 0.60, p<0.001). These early findings indicated that MSCT-based AVC quantification could reliably discriminate AS severity non-invasively, even with limited detector technology. Conclusions: This preliminary study established the feasibility of ECG-gated 4-slice MSCT for quantifying aortic valve calcification, demonstrating strong correlations with invasive hemodynamic measures of AS severity. The technique proved promising as a complementary non-invasive tool. Subsequent research with larger cohorts, echocardiography as the reference standard, and advanced multidetector systems (64–320+ detectors) validated and refined these observations. Current international guidelines (e.g., 2020 ACC/AHA and 2021 ESC/EACTS, with ongoing updates) strongly recommend non-contrast CT AVC scoring (Agatston method, typically 3 mm slices at 120 kV) in discordant or low-gradient AS cases. Sex-specific thresholds for severe AS are widely used: >2000 Agatston Units (AU) in men and >1200 AU in women (often “likely severe” at these levels, and “very likely severe” at ≥3000 AU in men and ≥1600 AU in women per ESC). Recent studies on contrast-enhanced CT propose adjusted thresholds (e.g., ≥1840 modified AU in men and ≥1430 in women). Modern protocols emphasize low-dose, prospective ECG-triggering, and iterative reconstruction to minimize radiation while supporting TAVI/TAVR planning, including annulus sizing, access evaluation, and risk stratification for complications like paravalvular leak or conduction disturbances. Keywords: Aortic stenosis, aortic valve calcification, multislice computed tomography, ECG-gating, Agatston score, cardiac catheterization, transcatheter aortic valve implantation, low-gradient aortic stenosis.