Aortic Valve Calcium Score Quantification by Contrast Cardiac CT: Correlations With Echocardiography and Optimal Thresholds.

Background: Aortic valve calcium score (AVCa) measured on noncontrast computed tomography (CT) is well-established for grading aortic stenosis (AS) severity. However, thresholds for AVCa measured on contrast CT remain uncertain. We evaluated correlations, associated factors, and severity thresholds of AVCa measured on contrast CT against transthoracic echocardiography (TTE) measures of AS.

Methods: Patients with native AS undergoing transcatheter aortic valve replacement evaluation from 2019 to 2020 who underwent TTE and contrast-enhanced CT were retrospectively studied (n=1035, age 79±9 years, 429 (41.5%) women, 906 (87.5%) severe and 129 (12.5%) moderate AS by TTE). AVCa was measured using the modified Agatston method with the minimum threshold of 4 SD above the mean ascending aorta blood pool Hounsfield units. Receiver-operating characteristics analysis and Youden index were used to define sex-specific optimal AVCa thresholds for identifying severe AS defined by TTE (aortic valve area by continuity equation ≤1.0 cm) in the derivation cohort and assessed when applied to the validation cohort.

Results: Mean aortic valve area on TTE was 0.79±0.21 cm, while mean AVCa score, volume, and mass were 2152±1102 modified AU, 1853±1592 mm, and 673±485 mg, respectively. Multivariable linear regression identified women to be associated with lower AVCa (β-coefficient, -358), while chronic kidney disease was associated with a higher AVCa (β-coefficient, 171). Optimal severe AS thresholds of ≥1840 modified AU for men and ≥1430 modified AU for women were determined, with area under curve (95% CIs) and sensitivities/specificities of 0.809 (0.749-0.869, 71.3%, 82.2%) for men and 0.822 (0.751-0.892), 73.4%/78.9% for women in the derivation cohort, and 0.830 (0.786-0.875), 75.9%/87.5% for men and 0.780 (0.670-0.890), 77.5%/71.4% for women in the validation cohort.

Conclusions: AVCa by contrast CT is a useful tool for identifying severe AS by TTE, with sex-specific thresholds for severe AS identified. Further studies are necessary to externally validate our findings and evaluate their prognostic significance.