Bone Tracers for Transthyretin Amyloid Cardiomyopathy: Are [^99mTc]Tc-DPD and [^99mTc]Tc-HMDP Equivalent?

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 [^99mTc]Tc-3,3-diphosphono-1,2-propanodicarboxylic acid ([^99mTc]Tc-DPD) and [^99mTc]Tc-hydroxy-methylene diphosphonate ([^99mTc]Tc-HMDP) intensity of myocardial uptake compared with background noise for ATTR-CM suspicion. Two hundred and seventy-four patients who underwent planar scintigraphy after intravenous injection of [^99mTc]Tc-DPD or [^99mTc]Tc-HMDP for ATTR-CM were included. The patients' current visual Perugini grades were retrieved. Regions of interest were measured on the heart (H) and on the contralateral mediastinum (CM), and H/CM ratios were calculated. Although the distribution of quantitative assessments of heart to contralateral mediastinum ratios is wider with [^99mTc]Tc-DPD, no difference in Perugini grades was found between [^99mTc]Tc-DPD and [^99mTc]Tc-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 <0.001 for [^99mTc]Tc-HMDP and for [^99mTc]Tc-DPD). We show in our local cohort that [^99mTc]Tc-DPD and [^99mTc]Tc-HMDP for amyloidosis diagnosis are equivalent for ATTR-CM diagnosis based on the Perugini grading scale.