CT-derived Extracellular Volume Fraction in Aortic Stenosis, Cardiac Amyloidosis, and Dual Pathology

Aims: To investigate CT-derived extracellular volume fraction (CT-ECV) in patients with lone aortic stenosis (AS), dual pathology of AS and transthyretin cardiac amyloidosis (AS-ATTR), and lone ATTR, and to examine the diagnostic performance and optimal cut-off values of CT-ECV for differentiating between patients with lone AS and AS-ATTR and between patients with lone AS and lone ATTR.

Methods And Results: This retrospective study included consecutive patients with severe AS (including lone AS and AS-ATTR) and lone ATTR who underwent CT-ECV analysis and technetium 99 m pyrophosphate (99mTc-PYP) scintigraphy. The diagnostic performance of CT-ECV for detecting cardiac amyloidosis was evaluated using the area under the receiver operating characteristic curve (AUC). Of 138 patients (mean age, 80 ± 8; 96 men), 55 had lone AS, 19 had AS-ATTR, and 64 had lone ATTR. CT-derived extracellular volume fraction of patients with lone AS was 31 ± 5%. CT-derived extracellular volume fraction was significantly lower in patients with AS-ATTR than lone ATTR (45 ± 12% vs. 53 ± 13%, P = 0.04). The AUC for differentiating patients with AS-ATTR from lone AS was lower than for lone ATTR from lone AS [0.90 (95% CI: 0.81, 0.96) vs. 0.95 (95% CI: 0.90, 0.98)]. The cut-off values of CT-ECV for differentiation between patients with lone AS and AS-ATTR were lower than those between patients with lone AS and lone ATTR [36.6% vs. 38.5% (Youden index)]. There was no significant difference in the proportion of 99mTc-PYP scintigraphy grade between patients with AS-ATTR and lone ATTR (P = 0.20).

Conclusion: Despite no significant difference in degree of ATTR between patients with AS-ATTR and lone ATTR, CT-ECV of patients with dual AS-ATTR pathology was significantly lower than that of patients with lone ATTR. The diagnostic performance and optimal cut-off values of CT-ECV for differentiating between patients with lone AS and AS-ATTR were lower than those between patients with lone AS and lone ATTR.