[99mTc]Tc-pyrophosphate (PYP) Scintigraphy Findings of Cardiac Amyloidosis: is It a Predictor for Survival?

Background Association [99mTc]Tc-pyrophosphate (PYP) uptake with survival of cardiac amyloidosis (CA) is still unkown. This study aimed to describe the scintigraphic findings of CA suspected cases and determine the prognostic value of scintigraphy. Methods Between September 2020-December 2023, all [99mTc]Tc-PYP scintigraphy images of CA suspected cases were evaluated retrospectively. The scintigraphy images were obtained 1h and 3h after intravenous injection of 740 MBq [99mTc]Tc-PYP. The quantitative and semiquantitative results of scintigraphy were analyzed, and their correlation with clinical outcomes was explored. Results Among the 268 cases (147 female, 121 male; median age:65), 12 (4.5%) were diagnosed with ATTR CA, 19 (7.1%) with AL CA. The median follow-up time was 386 days. ATTR CA cases exhibited significantly higher [99mTc]Tc-PYP uptake than AL CA and non-CA cases. The 1h and 3h heart-to-contralateral lung ratios were positively high degree correlated each other and SPECT/CT imaging reduced equivocal results from 82–37%. Eight of 19 patients with AL CA, one of 12 with ATTR CA, and 15 of non-CA cases died on follow-up. Median survival was 22 days in ATTR CA, 201 days in AL CA, and 105 days in non-CA ex cases. Survival analysis indicated significantly lower survival in non-CA cases compared to ATTR CA and AL CA. Conclusion [99mTc]Tc-PYP scintigraphy demonstrated varying uptake patterns in different CA forms. The study emphasizes the importance of combining scintigraphic findings with laboratory tests for accurate CA diagnosis and highlights the poor survival of individuals investigated for CA, even if the diagnosis is not confirmed.