Regional left ventricle involvement in cardiac transthyretin amyloidosis in SPECT/CT with [99mTc]Tc-DPD

Background Transthyretin amyloid (ATTR) cardiomyopathy is now more frequently diagnosed, partly due to advances in scintigraphic imaging and introduction of non-invasive diagnostic algorithms. Application of hybrid technique single-photon emission computed tomography and computed tomography (SPECT/CT) provides greater anatomic resolution, enabling the assessment of regional cardiac involvement. Purpose The aim of this prospective study was assessment of left ventricle involvement in patients with ATTR in SPECT/CT with [99mTc]Tc 3,3-disphono-1,2-propanodicarboxylic acid (DPD). Methods We present data based on evaluation of 100 patients, index patients with ATTR (group 1) and first-degree relatives (group 2) who were studied between June 2020 and December 2023. Study protocol included clinical data, free light chain blood immunoglobulins and urine immunofixation, transthoracic echocardiography (TTE) with global longitudinal strain (GLS) analysis, planar whole body acquisition and SPECT/CT with [99mTc]Tc-DPD, genetic testing by an amplicon-based next-generation TTR sequencing approach, and in selected cases cardiac or soft tissue biopsy. Results Study was conducted as multimodality and genetic cascade screening for relatives of individuals with ATTR. The population included hereditary ATTR (ATTRm) and ATTR wild type (ATTRwt). There were detected following types of TTR variants - Phe53Leu, Ala101Val, Glu112Lys, Glu109Lys, Glu122Lys, Glu82Lys. Overall, none of ATTRwt relatives expressed increased tracer uptake in scintigraphy. Overall, 26% first-degree relatives were diagnosed with pathogenic TTR variant and 7% had positive SPECT/CT with [99mTc]Tc-DPD. Importantly, among patients with positive SPECT/CT with [99mTc]Tc-DPD 58% presented asymmetrical left ventricle uptake. Overall, there were no differences in terms of radiotracer distribution between ATTRwt and ATTRm groups (p=0.85). Conclusions Regional left ventricle involvement in cardiac transthyretin amyloidosis can be assessed in SPECT/CT with [99mTc]Tc-DPD. The majority of patients present asymmetric cardiac uptake of radiotracer, both in the ATTRm and ATTRwt groups. Assessment of regional left ventricle involvement in cardiac transthyretin amyloidosis in SPECT/CT may in future translate into further enhancement of disease evaluation and improving prognosis in the group of patients.