Imaging cardiac amyloidosis: a pilot study using ¹⁸F-florbetapir positron emission tomography.

PURPOSE: Cardiac amyloidosis, a restrictive heart disease with high mortality and morbidity, is underdiagnosed due to limited targeted diagnostic imaging. The primary aim of this study was to evaluate the utility of (18)F-florbetapir for imaging cardiac amyloidosis.

METHODS: We performed a pilot study of cardiac (18)F-florbetapir PET in 14 subjects: 5 control subjects without amyloidosis and 9 subjects with documented cardiac amyloidosis. Standardized uptake values (SUV) of (18)F-florbetapir in the left ventricular (LV) myocardium, blood pool, liver, and vertebral bone were determined. A (18)F-florbetapir retention index (RI) was computed. Mean LV myocardial SUVs, target-to-background ratio (TBR, myocardial/blood pool SUV ratio) and myocardial-to-liver SUV ratio between 0 and 30 min were calculated.

RESULTS: Left and right ventricular myocardial uptake of (18)F-florbetapir were noted in all the amyloid subjects and in none of the control subjects. The RI, TBR, LV myocardial SUV and LV myocardial to liver SUV ratio were all significantly higher in the amyloidosis subjects than in the control subjects (RI median 0.043 min(-1), IQR 0.034 - 0.051 min(-1), vs. 0.023 min(-1), IQR 0.015 - 0.025 min(-1), P = 0.002; TBR 1.84, 1.64 - 2.50, vs. 1.26, IQR 0.91 - 1.36, P = 0.001; LV myocardial SUV 3.84, IQR 1.87 - 5.65, vs. 1.35, IQR 1.17 - 2.28, P = 0.029; ratio of LV myocardial to liver SUV 0.67, IQR 0.44 - 1.64, vs. 0.18, IQR 0.15 - 0.35, P = 0.004). The myocardial RI, TBR and myocardial to liver SUV ratio also distinguished the control subjects from subjects with transthyretin and those with light chain amyloid.

CONCLUSION: (18)F-Florbetapir PET may be a promising technique to image light chain and transthyretin cardiac amyloidosis. Its role in diagnosing amyloid in other organ systems and in assessing response to therapy needs to be further studied.