Correlation of 99mTc-DPD bone scintigraphy with histological amyloid load in patients with ATTR cardiac amyloidosis.

Background: The significance of measuring 99mTc-labelled-3,3-diphosphono-1,2-propanodicarboxylic acid (99mTc-DPD) in transthyretin (ATTR) cardiac amyloidosis has not been adequately studied. This single-centre observational study evaluated the correlation between 99mTc-DPD scintigraphy and histological amyloid load in endomyocardial biopsy (EMB).

Methods: Twenty-eight patients with biopsy-proven ATTR amyloidosis and concomitantly available 99mTc-DPD scintigraphy were included. Visual Perugini scoring, and (semi-)quantitative analysis of cardiac 99mTc-DPD uptake by planar whole-body imaging and single photon emission computed tomography (SPECT/CT) using regions of interest (ROI) were performed. From this, heart-to-whole-body ratio (H/WB) and heart-to-contralateral-chest ratio (H/CL) were calculated. The histological amyloid load was quantified using two different staining methods.

Results: Increased cardiac tracer uptake was documented in all patients (planar: ROImean 129 ± 37 cps; SPECT/CT: ROImean 369 ± 142 cps). Histological amyloid load (19 ± 13%) significantly correlated with Perugini score (r = 0.69, p < .001) as well as with cardiac 99mTc-DPD uptake (planar: r = 0.64, p < .001; H/WB: r = 0.50, p = .014; SPECT/CT: r = 0.53, p = .008; H/CL: r = 0.43, p = .037) (results are shown for correlations with Congo Red-staining).

Conclusion: In ATTR, cardiac 99mTc-DPD uptake significantly correlated with histological amyloid load in EMB. Further studies are needed to implement thresholds in cardiac 99mTc-DPD uptake measurements for risk stratification and guidance of therapy.