Usefulness of (99m)Tc-HMDP scintigraphy for the etiologic diagnosis and prognosis of cardiac amyloidosis.

BACKGROUND

Amyloidosis is characterized by extracellular deposits of insoluble proteins that cause tissue damage. The three main types are monoclonal light chain (AL), wild-type transthyretin (wt-TTR) and mutated transthyretin (m-TTR) amyloidosis. Cardiac amyloidosis (CA) raises diagnostic challenges.

OBJECTIVE

To assess the diagnostic accuracy of (99m)Tc-HMDP-scintigraphy for typing CA, differentiating CA from non-amyloid left ventricle hypertrophy (LVH), and predicting outcomes.

METHODS

121 patients with suspected CA underwent (99m)Tc-HMDP-scintigraphy in addition to standard investigations.

RESULTS

CA was diagnosed in all AL (n = 14) and wt-TTR (n = 21). Among m-TTR (n = 34), 26 had CA, 4 neuropathy without CA and 4 were asymptomatic carriers. Of the 52 patients with non-amyloid heart disease, 37 had LVH and served as controls. (99m)Tc-HMDP cardiac uptake occurred in all wt-TTR, in m-TTR with CA except two and in one AL. A visual score ≥ 2 was 100% specific for diagnosing TTR-CA. Among TTR-CA, heart-to-skull retention (HR/SR) correlated with CA severity (LVEF and NT-proBNP). Median follow-up was 111 days (50;343). In a multivariate Cox model including clinical, echocardiographic and scintigraphic variables, NYHA III-IV and HR/SR > 1.94 predicted acute heart failure and/or death.

CONCLUSIONS

This preliminary study suggests that (99m)Tc-HMDP-scintigraphy may aid differentiation between transthyretin and AL-CA as well as CA from other LVHs. (99m)Tc-HMDP-scintigraphy appears to provide prognostic information in CA.