Aortic valve tissue quantification in bicuspid aortic valve stenosis

Abstract

Abstract Background The relative contribution of calcific versus noncalcific aortic valve tissue volume to aortic stenosis (AS) in bicuspid aortic valve (BAV) is unclear. Purpose We aimed to assess the association of aortic valve tissue volume quantified by contrast-enhanced CT with echocardiographic AS severity, and diagnostic implication of noncalcific tissue volume for severe AS. Methods We retrospectively identified 234 patients with BAV who had echocardiographic AS severity and contrast-enhanced CT evaluation within six months and left ventricular ejection ≥50%, including 150 severe AS (aortic valve area≤1 cm2 or indexed valve area≤0.6cm2/m2 plus mean grdient≥40mmHg or peak velocity≥4 m/s), 84 nonsevere AS (61 with at least mild AS: peak veloicty≥2.0 m/s plus mean gradient ≥10mmHg, and 23 with normal aortic valve function). Contrast-enhanced CT aortic valve calcific volume and noncalcific (fibrosis) volume were quantified using patient-specific Hounsfield unit thresholds (Figure). Noncontrast CT aortic valve calcium score (AVCscore) was quantified by the Agaston method. CT measurements were indexed to echocardiographic aortic valve annulus area and square-root transformed for the analysis. Results Of 234 patients, the mean age was 64±11 years, and 64% were men. There were positive correlations of indexed calcific volume, noncalcific volume, and inverse correlations of percentages of noncalcific volume (noncalcific volume divided by the sum of calcific and noncalcific volume) with peak velocity and mean gradient (|r|=0.30 to 0.68). Among 150 patients with severe AS, 28 had an AVCscore below the severe AVC threshold (1200 AU in women and 2000 AU in men) while exhibited a higher percentage of noncalcific volume compared to 122 patients with severe AVCscore (67±15% vs. 39±15%, p<0.001). After excluding 122 patients with severe AS and severe AVCscore, the indexed noncalcific volume was associated with severe AS (β±S.E: 0.18±0.07, p=0.005) with an area under the curve of 0.71; in contrast, AVCscore was not (p=0.55). Conclusion Both calcific and noncalcific aortic valve tissue volume contribute to AS severity in patients with BAV. Notably, noncalcific tissue volume is a key factor in determining severe AS in patients without severe AVCscore, suggesting its potential diagnostic value.Figure