OP2 Fibrocalcific Volume Assessment in Aortic Stenosis

Introduction To evaluate the aortic valve fibrocalcific volume by computed tomography (CT) angiography in patients with aortic stenosis (AS). In particular, to assess its reproducibility, association with disease severity, its ability to predict and track AS progression and to perform histological validation. Methods In a post-hoc analysis of 136 patients with AS participating in the SALTIRE 2 trial, fibrocalcific volume was calculated using semi-automated software on CT-angiograms at baseline and after one year. The distributions of CT-attenuation were analysed using Gaussian mixture modelling to derive thresholds for aortic valve tissue types enabling the quantification of calcific, non-calcific and fibrocalcific volumes indexed to annulus area. Scan-rescan reproducibility was assessed. Aortic valves from 41 patients undergoing valve replacement were included in the histological validation cohort. Results Fibrocalcific volume measurements demonstrated excellent scan-rescan reproducibility (mean difference -1%, limits of agreement -4.5% to 2.8%). Baseline fibrocalcific volumes correlated with baseline mean aortic valve gradients on echocardiography in both men and women (rho=0.64 and 0.69 respectively; p<0.001 for both). The relationship was driven principally by calcific volume in men and fibrotic volume in women. After one year, fibrocalcific volume increased by 17% and correlated with an increase in mean gradient (rho=0.32, p=0.003). Baseline fibrocalcific volume was the strongest predictor of disease progression on multivariable analysis, with a particularly strong association in women (rho=0.75, p<0.001). Histologically, there was a good correlation between fibrocalcific volume and valve weight (r=0.51, p<0.001). Furthermore, non-calcific volumes on CT were higher in patients with a higher fibrosis score on histology and similarly calcific volumes on CT were higher in patients with higher Warren-Yong scores for calcification on histology. Conclusions The fibrocalcific volume is a highly reproducible, anatomic, CT-derived assessment of AS. It correlates with AS severity and haemodynamic progression and there is good correlation between fibrocalcific volume and histological parameters.