Background Amyloidosis is characterised by the extracellular deposition of misfolded protein, markedly increasing the myocardial extracellular volume (ECV). Cardiac transthyretin amyloidosis co-exists in up to 1 in 7 elderly patients with severe aortic stenosis (AS) referred for transcatheter aortic valve implantation (TAVI).^99mTc-3,3-diphosphono-1,2-propanodicarboxylic acid (DPD) scintigraphy can detect this, but screening patients using ECV quantification by computed tomography (ECV_CT) in the same sitting as their TAVI work-up CT is an attractive concept, which we sought to investigate.

Methods Elderly patients (aged ≥75) with severe AS referred for TAVI were recruited as part of the ATTRact-AS study (NCT03029026). DPD scans were graded using the Perugini scoring system. Additional pre- and 3 min post contrast ‘axial shuttle mode’ datasets were acquired for ECV_CT. These datasets were averaged, registered with the CT angiogram and subtracted. Inputting the haematocrit enabled estimation of the myocardial ECV.

Results 30 patients underwent ECV_CT (aged 87±6 years, 43% male), including 10 with evidence of cardiac amyloid on DPD scintigraphy (4 Perugini grade 1, 6 grade 2). Total myocardial ECV_CT was 29%±3% for grade 0, 31±4% for grade 1 and 41%±9% for grade 2 (p<0.001 by ANOVA). ROC analysis showed an AUC of 0.90 (95% CI: 0.77 to 1.00) for grade 2 and 0.81 (85% CI: 0.63 to 0.98) for grade 1 or 2. Mean total dose-length product for the additional scans was 375±37 mGy.cm.

Conclusions In the elderly with severe AS, ECV_CT performed with a 3 min post-contrast scan, can detect cardiac amyloid and could be used as a screening tool.