Usefulness of scintigraphy with [99mTc]Tc-DPD for the detection of transthyretin cardiac amyloidosis. Reference centre experience in an endemic area

Abstract Background Cardiac amyloidosis (CA) is an infiltrative disorder caused by protein deposition, being transthyretin amyloidosis (ATTR) and primary amyloidosis (AL) the most common forms of CA. ATTR can occur in a hereditary form (ATTRv) or wild-type (ATTRwt). Our area is endemic for ATTRv due to the Val30Met mutation. Purpose To analyse the usefulness of scintigraphy with [99mTc]Tc-DPD (DPD-CS) in an endemic area and its relationship with the diagnostic of CA. Methods We conduct a retrospective study (04/2013-12/2022) of DPD-CS performed for suspected/screening of CA. Our acquisition protocol consists of performing planar images after 3h p.i.(anterior, left anterior oblique and left lateral) +/- SPECT/CT. The assessment of myocardial uptake was evaluated using the Perugini scale (PS: 0-3), considering 2 and 3 as positive scans. DPD-CS results were classified based on the suspicion of CA, according to the 2021 ESC guidelines (we considered cardiomyopathy if: left ventricle hypertrophy ≥12 mm + ≥3 typical signs/symptoms), as well as according to their final diagnosis: ATTRv, asymptomatic carriers, ATTRwt, AL, AA and other non-amyloid (NA) causes. Clinical findings were correlated with the results of the DPD-CS. Results 509 DPD-CS were performed in 478 patients (median age:73 years [22-95], 62% men). Median follow-up: 4.17 years. 127/478 patients were classified with cardiomyopathy (131/509 DPD-CS) and 351/478 without cardiomyopathy (378/509 DPD-CS). 115/509 positive DPD-CS (PS-2: 17, PS-3: 98): 113 had cardiomyopathy (55 ATTRv, 60 ATTRwt) and 2 without cardiomyopathy (1 ATTRv, 1 asymptomatic carrier). These latter two patients developed cardiomyopathy during the follow-up. 394/509 negative DPD-CS (PS 0: 387, PS 1: 7): 18 with cardiomyopathy (1 ATTRv, 1 carrier, 3 AL and 13 NA) and 376 without cardiomyopathy (30 asymptomatic carriers, 88 ATTRv, 2 AA, 9 AL and 247 NA). One patient with cardiomyopathy and ATTRv had initial negative DPD-CS, but became positive DPD-CS on follow-up. All ATTRv without cardiomyopathy presented polyneuropathy. Final diagnoses (according to DPD-CS number): 143 ATTRv (140 Val30Met, 2 Val122Ile, 1 Glu495Gln), 32 carriers (29 Val30Met, 2 Val122Ile, 1 His51Asn), 61 ATTRwt,12 AL, 2 AA and 259 NA. The analysis obtained after correlating the results of the DPD-CS regarding the presence of cardiomyopathy was: sensitivity 86.25%, specificity 99.47%, PPV 98.26% and NPV 95.43%. Conclusion Our study reaffirms the usefulness of DPD-CS in the non-invasive diagnosis of transthyretin CA. DPD-CS has an additional value in endemic areas for the early detection of CA in asymptomatic patients.