Quantification of aortic valve calcification on contrast-enhanced CT of patients prior to transcatheter aortic valve implantation

Aims: The aim of the study was to develop a formula enabling the quantification of aortic valve calcification (AVC) on contrast-enhanced CT of patients undergoing transcatheter aortic valve implantation (TAVI). Methods and results: Two hundred and seventeen (217) consecutive patients with severe aortic valve stenosis undergoing non-enhanced electrocardiography-gated CT angiography (NECT) and contrast-enhanced electrocardiography-gated CT angiography (CECT) prior to TAVI were subdivided into a training cohort (n=145) and a validation cohort (n=72). Aortic valve calcification (AVC) was semi-automatically segmented on CECT (AVC(CE)). Agatston score (AS) quantified on NECT served as reference standard. Applying a linear regression model, we derived a formula for quantification of the AS on CECT in the training cohort (2.27+1.04x(3)root AVC(CE))(3.) Testing the formula in CECT of the validation cohort yielded a calculated median AS of 2,339 (interquartile range [IQR]: 1,609-3,643), being not significantly different to the reference standard AS based on NECT (median 2,455, IQR: 1,503-3,611, p=0.452). Intra-class correlation coefficient (0.897) and Bland-Altman analysis (mean difference of scores: -0.75) showed excellent agreement. As a rule of thumb, the formula AS=2xAVC(CE) may be applied to calculate the AS. Conclusions: We introduced a formula enabling the accurate quantification of AVC on CECT, to speed up clinical workflow in cases where NECT scans are initially not available and to assist echocardiography in assessing aortic stenosis severity.