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

Background/Introduction 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 ocurr in a hereditary form (ATTRv) or wild-type (ATTRwt). Our area is endemic for ATTRv due to the Val50Met mutation. Purpose Analyze the usefulness of scintigraphy with [99mTc]Tc-DPD (DPD-CS) in an endemic area and its relationship with the diagnostic of CA. Methods 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 2-3 as positive scans. DPD-CS results were classified based on the suspicion of CA, according to the guidelines of the ESC 2021 (we considered cardiomiopathy if: LVH ≥12 mm + ≥3 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 1145 509 DPD-CS were performed in 478 patients (median age:73 years[22-95], 62% men). Median follow-up: 4.17 años. 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, 58 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). The only patient with cardiomyopathy and ATTRV, had initial negative DPD-CS with following positive DPD-CS. All ATTRv without cardiomyopathy presented only polyneuropathic disease. Final diagnoses (according to DPD-CS number): 146 ATTRv (144 Val50Met, 2 Val142Ile), 32 carriers, 58 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 cardiomyopathy due to ATTR. DPD-CS has an additional value in endemic areas for the early detection of CA in asymptomatic patients.