The role of serial 99mTc-DPD scintigraphy in monitoring cardiac transthyretin amyloidosis.

PURPOSE: Cardiac transthyretin amyloidosis is a usually fatal form of restrictive cardiomyopathy for which clinical trials of treatments are ongoing. It is anticipated that quantitative nuclear medicine scintigraphy, which is experiencing growing interest, will soon be used to evaluate treatment efficacy. We investigated its utility for monitoring changes in disease load over a significant time period. METHODS: Sixty-two treatment-naive patients underwent 99mTc-labelled 3,3-diphosphono-1,2propanodicarboxylic acid (99mTc-DPD) scintigraphy two to four times each over a five-year period. Quantitation of cardiac 99mTc-DPD retention was performed according to two established methods: measurement of heart-to-contralateral ratio (H/CL) in the anterior view (planar) and percentage of administered activity in the myocardium (SPECT). RESULTS: In total 170 datasets were analysed. Increased myocardial retention of 99mTc-DPD was demonstrable as early as 12 months from baseline. Year-on-year progression across the cohort was observed using SPECT-based quantitation, though on 30 occasions (27.8%) the change in our estimate was negative. CONCLUSIONS: The spread of our results was notably high compared to the year-on-year increases. If left unaccounted for, variance may draw fallacious conclusions about changes in disease load. We therefore urge caution in drawing conclusions solely from nuclear medicine scintigraphy on a patient-by-patient basis, particularly across a short time period.

99mTc-DPD scintigraphy in immunoglobulin light chain (AL) cardiac amyloidosis.

AIMS: Technetium-99m-labelled 3,3-diphosphono-1,2-propanodicarboxylic acid (99mTc-DPD scintigraphy) is recognized as highly accurate for the non-invasive diagnosis of transthyretin (ATTR) cardiac amyloidosis (CA). A proportion of patients with immunoglobulin light chain (AL) CA have also been reported to show cardiac 99mTc-DPD uptake. Herein, we assessed the frequency and degree of cardiac 99mTc-DPD uptake and its clinical significance among patients with AL CA. METHODS AND RESULTS: Between 2010 and 2017, 292 consecutive patients with AL CA underwent 99mTc-DPD scintigraphy and were included in this study: 114 (39%) had cardiac 99mTc-DPD uptake: grade 1 in 75%, grade 2 in 17%, and grade 3 in 8% of cases. Patients with cardiac 99mTc-DPD uptake had poorer cardiac systolic function and higher N-terminal pro-brain natriuretic peptide. No differences were noted in cardiac magnetic resonance parameters between patients with and without cardiac 99mTc-DPD uptake (N = 19 and 42, respectively). Patients with cardiac 99mTc-DPD uptake showed a trend to worse survival than those with no uptake (log-rank P = 0.056). Among 22 patients who underwent serial 99mTc-DPD scintigraphy, 5 (23%) showed reduction in the grade of cardiac uptake. CONCLUSIONS: In this large cohort of patients with AL CA, 99mTc-DPD scintigraphy ∼40% of cases showed cardiac uptake, including grade 2-3 in 10% of all patients (25% of those with cardiac 99mTc-DPD uptake). Cardiac 99mTc-DPD uptake was associated with poorer cardiac function and outcomes. These data highlight the critical importance of ruling out AL amyloidosis in all patients with cardiac 99mTc-DPD uptake to ensure such patients are not assumed to have ATTR CA.