Early-phase myocardial uptake intensity of 99mTc-HMDP vs 99mTc-DPD in patients with hereditary transthyretin-related cardiac amyloidosis

This study sought to compare the intensity of early-phase myocardial uptake of two phosphonate-based radiotracers, 99mTc-hydroxymethylene diphosphonate (HMDP) and 99mTc-3,3-diphosphono-1,2-propanodicarboxylic acid (DPD), in patients with hereditary transthyretin-related cardiac amyloidosis (TTR-CA). Six patients with biopsy-proven diagnosis of TTR-CA and characteristic amyloid fibril composition underwent early-phase 99mTc-HMDP myocardial scintigraphy as part of their routine workup; they were later assessed by 99mTc-DPD scintigraphy after having signed informed written consent. Heart-to-mediastinum-ratio was measured at both time points as well as regional distribution on 17-segment analysis. All patients had an H/M ratio >1.28 on both imaging. 99mTc-DPD uptake was slightly higher than 99mTc-HMDP uptake in 3 patients, but no statistical difference was found (P = 0.13). Regional distribution of the two radiotracers was well correlated on bull’s eyes analysis, with only slight underestimation of 99mTc-DPD uptake in the anterior/apical segments, compared with 99mTc-HMDP. 99mTc-HMDP and 99mTc-DPD show comparable myocardial uptake intensity on early-phase scintigraphy and can be used alternatively for the diagnosis of TTR-CA.