Role of cardiac scintigraphy with ⁹⁹mTc-DPD in the differentiation of cardiac amyloidosis subtype.

Introduction And Objectives: We investigated the diagnostic accuracy of (99m)Tc-3,3-diphosphono-1,2 propanodicarboxylic acid ((99m)Tc-DPD) scintigraphy in differentiating between monoclonal immunoglobulin light chain and transthyretin-related cardiac amyloidosis.

Methods: Nineteen patients with documented cardiac amyloidosis were included: 8 with transthyretin-related amyloidosis (group A) and 11 with light chain amyloidosis (group B). All the patients underwent scintigraphy with (99m)Tc-DPD and (99m)Tc-methylene diphosphonate ((99m)Tc-MDP).

Results: On visual scoring, cardiac (99m)Tc-DPD uptake could be characterized as moderate to severe (scores of 2-3), with ventricular or biventricular distribution, in all group A patients (transthyretin-related cardiac amyloidosis), and was absent or mild (scores of 0-1) and diffusely distributed in all group B patients (monoclonal immunoglobulin light chain cardiac amyloidosis). (99m)Tc-DPD uptake was also absent (score of 0) among unaffected controls and in 2 unaffected relatives of patients with hereditary transthyretin-related amyloidosis who harbor a mutation in the TTR gene. With (99m)Tc-MDP, all the patients had a myocardial uptake score of 0-1. In our series, selective myocardial uptake of (99m)Tc-DPD provided 100% accuracy (95% confidence interval, 97.37%-100%) for the differentiation between transthyretin-related and monoclonal immunoglobulin light chain cardiac amyloidosis.

Conclusions: We conclude that (99m)Tc-DPD scintigraphy is a useful test for the differential diagnosis of transthyretin vs monoclonal immunoglobulin light chain etiology in patients with cardiac amyloidosis.