^99mTc HMDP myocardial scintigraphy is predictive of major adverse cardiac event (MACE) in patients with transthyretin-type (TTR) amyloidosis

Objectives Amyloidosis is characterized by extracellular deposits of insoluble proteins with 3 main types: monoclonal light chain (AL), wild-type transthyretin (wt-TTR), and mutated transthyretin (m-TTR). We evaluated the prognostic value of ^99mTc-HMDP myocardial scintigraphy in patients with TTR amyloidosis.

Methods Out of 121 consecutive patients, 55 patients were diagnosed with TTR amyloidosis. All underwent ^99mTc-HMDP scintigraphy using a dual-headed gamma camera. Acquisitions consisted of a whole-body scan and a cardiac tomography, acquired both at 10 min (early soft-tissue phase) and 3 h (delayed bone phase) following the injection (650 MBq i.v.). Myocardial uptake of ^99mTc-HMDP was assessed visually (score 0-3) and semi-quantitatively (heart-to-skull retention [HR/SR]).

Results Among 55 TTR patients, 47 had cardiac amyloidosis (wt-TTR-CA in 21 and m-TTR-CA in 26 patients). Delayed myocardial ^99mTc- HMDP uptake occurred in all wt-TTR-CA, in all but 2 m-TTR-CA. All patients with TTR-CA had a positive HMDP myocardial scintigraphy. Except 1 wt-TTR-CA and 5 m-TTR-CA who had a score of 1, all others had a score ≥2. To note, scintigraphy was negative in the 8 patients without cardiac amyloidosis at early and delayed phase. Among 55 TTR patients, HR/SR ratio was correlated with CA severity (LVEF and NT-proBNP). Median follow-up was 111 d (50-343). Patients with HR/SR<1.94 had better 6-mo MACE-free survival (95%) than those with HR/SR>1.94 (60%, P=0.025). Interestingly, combining NYHA class with HR/SR ratio allowed to identify prognostic groups of patients ranging from 100% MACE-free survival to 44%.

Conclusions ^99mTc-HMDP myocardial scintigraphy is predictive of MACE-free survival in TTR amyloidosis, particularly in combination with NYHA classification.