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 (ECVCT) 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 ECVCT. These datasets were averaged, registered with the CT angiogram and subtracted. Inputting the haematocrit enabled estimation of the myocardial ECV.
Results 30 patients underwent ECVCT (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 ECVCT 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, ECVCT performed with a 3 min post-contrast scan, can detect cardiac amyloid and could be used as a screening tool.
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