[99mTc]Tc-Pyrophosphate Scintigraphy for Cardiac Amyloidosis: Evaluation of Scintigraphy Findings and Their Prognostic Value

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Abstract Association of [99mTc]Tc-pyrophosphate (PYP) uptake with survival of cardiac amyloidosis (CA) is still unknown. This study aimed to describe the scintigraphic findings of CA suspected cases and determine the prognostic value of scintigraphy. Between September 2020 and December 2023, all [99mTc]Tc-PYP scintigraphy images of CA suspected cases were evaluated retrospectively. The scintigraphy images were obtained 1 and 3 hours after intravenous injection of 740 MBq [99mTc]Tc-PYP. The quantitative and semiquantitative results of scintigraphy were analyzed, and their correlation with survival was evaluated. Among the 268 cases (147 females, 121 males; median age: 65), 12 (4.5%) were diagnosed with transthyretin (ATTR) CA and 19 (7.1%) with light chain (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 1- and 3-hour heart-to-contralateral lung ratios were positively highly correlated with each other, and SPECT/CT (single-photon computed tomography/computed tomography) imaging reduced equivocal results from 82 to 37%. Eight of the AL CA cases (42.1%), 1 ATTR CA case (8.3%), and 15 of non-CA cases (6%) died on follow-up. Median survival was 22 days in ATTR CA, 201 days in AL CA, and 105 days in non-CA deceased cases. Survival analysis indicated significantly lower survival in non-CA cases compared with ATTR CA and AL CA. [99mTc]Tc-PYP scintigraphy is highly sensitive and specific for detecting ATTR CA and differentiating from AL CA. Even in the absence of a diagnosis of CA, the fact that survival may be short in cases with high uptake on scintigraphy should be considered in the follow-up of these cases.

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