9 Assessment of aortic valve calcification using contrast-enhanced computed tomography

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Abstract

Introduction

Aortic valve calcification (AVC) has been proposed as the main force driving progression of aortic stenosis. Non-contrast computed tomography (CT) can reproducibly quantify AVC and correlates well with echocardiographic measures of severity. However, contrast-enhanced CT presents the opportunity to quantify AVC whilst also providing important information about spatial distribution of calcium and non-calcific thickening of leaflets.

Methods

CT scans of 113 consecutive patients assessed for transcatheter aortic valve implantation (TAVI) at the Edinburgh Royal Infirmary were analysed. Contrast-enhanced CT images were reconstructed in the short-axis plane of the aortic valve to measure valve dimensions, quantify AVC (volume, mm3) and document spatial distribution of calcium. Three methods were compared for defining the radiodensity threshold above which calcium was detected and a scoring system was applied to describe calcium distribution.

Results

AVC can be detected using contrast-enhanced CT and is likely to benefit from a threshold adjusted according to contrast load. Males were found to have higher AVC volume than females (mean 1069mm3 vs. 817.7 mm3, p=0.0058), even when adjusted for annular diameter (p=0.0435). The non-coronary cusp was the most heavily calcified cusp (p<0.001) and a correlation was seen between increasing cusp calcification and progressive involvement of the free edge tending toward a complete arc of calcium.

Conclusions

Contrast-enhanced CT allows for quantification of AVC and the optimal method must now be validated against non-contrast CT. Contrast CT provides valuable additional information about valve anatomy and AVC location which are likely to contribute to the haemodynamic severity of aortic stenosis.

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