Expanding the role of bone-avid tracer cardiac single-photon emission computed tomography/ computed tomography: assessment of treatment response in transthyretin amyloid cardiomyopathy.

This editorial focuses on the use of quantitative single-photon emission computed tomography/computed tomography (SPECT/CT) with technetium-99m-labeled 3,3-diphosphono-1,2-pyrophosphate (99mTc-DPD) to monitor treatment response to tafamidis in transthyretin amyloid cardiomyopathy (ATTR-CM). The study by Rettl et al. evaluated changes in myocardial DPD uptake using a novel retention index before and after tafamidis therapy, finding heterogeneous treatment responses with some patients showing functional cardiac improvements on cardiac MRI despite no significant structural changes overall. The editorial highlights uncertainties regarding the precise mechanism of DPD uptake and the clinical significance of changes in retention index, emphasizing the need for further research on quantitative SPECT/CT’s reproducibility and its role in assessing emerging ATTR therapies.