Quantifying Aortic Valve Calcification using Coronary Computed Tomography Angiography

Introduction

Aortic valve calcification (AVC) has been associated with major adverse cardiovascular events and all-cause mortality. We sought to develop and validate a method to quantify AVC using coronary CT angiography (CTA).

Methods

Of 59 patients who underwent both non-contrast and contrast enhanced coronary CTA, 25 patients served as the derivation cohort and 34 patients served as the validation cohort. For non-contrast enhanced CT, quantification of AVC was performed using the Agatston method for coronary artery calcification (CAC). For contrast enhanced coronary CTA, a region of interest (ROI) was placed in the ascending aorta and the mean aortic attenuation value (HU_Aorta) and standard deviation (SD) were measured. Using a calcium threshold of mean HU_Aorta + 2SD, the AVC_CTA was calculated. All other Agatston score parameters (weighting factors and area calculations) remained unchanged.

Results

In the derivation cohort, the correlation between AVC_CAC and AVC_CTA was excellent (r = 0.982). Using the line of best fit, a correction factor was calculated enabling the conversion of AVC_CTA results to a AVC_CAC equivalent (AVC_Corrected = 1.868 × AVC_CTA). Using this correction in the validation cohort, the correlation and agreement between AVC_CAC and AVC_Corrected were good (ICC = 0.939; 95% CI: 0.881–0.969; kappa = 0.700; 95% CI: 0.469–0.931).

Conclusion

The quantification of AVC_Corrected using contrast enhanced CTA is feasible using a systematic approach with very good reliability and good agreement with AVC_CAC. Larger-scale validation studies are needed to determine whether the use of AVC_CAC can be eliminated in favour of AVC_Corrected.