Indexed Aortic Valve Calcium Volume by Computed Tomography Angiography in Patients With Aortic Stenosis

Background
Calcium scoring from noncontrast computed tomography (CT) is used clinically to adjudicate aortic stenosis severity in patients with discordant echocardiography.
Objectives
The aim of this study was to investigate whether quantification of aortic valve calcium volume from computed tomography angiography (CTA) can provide robust diagnostic discrimination of disease severity and inform risk stratification of patients with aortic stenosis.
Methods
Patients with mild to severe aortic stenosis who underwent concurrent CTA and echocardiography were included in a retrospective international multicenter observational cohort study. Accuracy of aortic valve calcium volume to diagnose severe aortic stenosis in patients with concordant disease on echocardiography was assessed. Association of aortic valve calcium volume with the incidence of aortic valve replacement or all-cause death was investigated.
Results
The study included 1,521 patients (mean age: 74 ± 10 years; 44% female; median peak aortic jet velocity: 3.8 m/s [Q1-Q3: 3.1-4.5 m/s]). Indexed aortic valve calcium volume correlated with peak aortic jet velocity (ρ = 0.723; P < 0.001) and noncontrast CT calcium score (ρ = 0.896; P < 0.001). In the derivation cohort (n = 689), sex-specific thresholds for indexed calcium volume (men: 122 mm3/cm2; women: 61 mm3/cm2) provided excellent diagnostic discrimination for severe aortic stenosis (C-statistic: 0.900 for men; 0.926 for women). Similar diagnostic discrimination was observed in the validation cohort (n = 459; C-statistic: 0.933 for men; 0.944 for women). Clinical outcomes were available in 711 patients (25% with discordant echocardiography), with 249 reaching the primary endpoint after 26 months (Q1-Q3: 12-53 months). Indexed calcium volume thresholds were independently associated with aortic valve replacement or all-cause mortality in both the cohort as a whole (HR: 2.01 [95% CI: 1.30-3.10]; P < 0.01) and those with discordant echocardiography (HR: 1.58 [95% CI: 1.01-2.44]).
Conclusions
In patients with aortic stenosis, indexed aortic valve calcium volume from CTA provides accurate discrimination of disease severity and additive prognostic information. This technique can be easily applied to patients undergoing CTA for transcatheter aortic valve replacement or coronary artery evaluation without the need for a separate noncontrast CT scan.