Bone tracers for transthyretin amyloid cardiomyopathy: are 99mTcTc-DPD and 99mTcTc-HMDP truly equivalent?

Abstract Background The management of transthyretin amyloid cardiomyopathy (ATTR-CM) has revolved around the scintigraphic diagnosis since the introduction of a specific treatment; however, the equivalency of the bone radiotracers remains unclear. This retrospective monocentric observational study compared 99m TcTc-3,3-diphosphono-1,2-propanodicarboxylic acid ( 99m TcTc-DPD) and 99m TcTc-hydroxy-methylene diphosphonate ( 99m TcTc-HMDP) for ATTR-CM diagnosis. Methods One hundred and twenty-nine patients who underwent single photon emission computed tomography (SPECT/CT) after intravenous injection of 99m TcTc-DPD or 99m TcTc-HMDP for ATTR-CM were included. The patients’ current visual Perugini grades were retrieved. Regions of interest (ROI) were measured on the heart (H) and on contralateral mediastinum (CM), and H/CM ratios were calculated. Results Although the distribution of quantitative assessments of heart to contralateral mediastinum ratios is wider with 99m TcTc-DPD, suggesting a trend towards improved diagnosis, no difference in Perugini grades was found between 99m TcTc-DPD or 99m TcTc-HMDP for the diagnosis of ATTR-CM in evocative/non-evocative conditions. There was no difference in ATTR-CM diagnosis between the 2 tracers with a threshold of 1.5 (p-value = 3.316*10 −10 for 99m TcTc-HMDP and p-value = 2.59*10 −15 for 99m TcTc-DPD). Conclusions We show in our local cohort that 99m TcTc-DPD and 99m TcTc-HMDP for amyloidosis diagnostic are equivalent for ATTR-CM diagnosis based on the Perugini grading scale. With 99m TcTc-DPD, a wider range of the H/CM ratio was noted, which may be considered as a better discrimination of the disease by this bone tracer. Additional research with a final diagnosis of the disease is necessary to evaluate the utility of this quantitative evaluation.