Pitfalls of the Semi-Quantitative Analyzing ^99mTc-Pyrophosphate Planar Images for Diagnosing Transthyretin Cardiac...

Two different approaches, 1-h heart-to-contralateral (H/CL) ratio and 3-h visual grading scale relative to ribs (VGSr), have been established to interpret ^99mTc-PYP planar images for the detection of amyloid transthyretin cardiac amyloidosis (ATTR-CA). Since they are prone to pitfalls, this pilot study aimed to explore the diagnostic practicality of the 3-h visual grading scale relative to the upper segment of sternum (VGSs) approach for interpreting ^99mTc-PYP planar images.

A total of 42 patients were enrolled in this retrospective study. SPECT/CT approach and planar approaches including H/CL ratio, VGSr, and VGSs were utilized to interpret the ^99mTc-PYP images obtained at both 1 and 3 h. The classification criteria of the latest expert consensus recommendations were considered as the gold standard. The concordance between the interpretation of each approach and the gold standard was investigated.

In addition to 1- and 3-h SPECT/CT approaches, the interpretation of planar images using the 3-h VGSs approach was also applicable, which turns identical to the gold standard (κ = 1.000; p < 0.001).

For the interpretation of ^99mTc-PYP planar images, the 3-h VGSs approach should be the optimal method, particularly in the case without available or feasible tomography imaging. Only one imaging session (planar and SPECT/CT) at 3 h would be sufficient for the detection of ATTR-CA, and favorable for patient satisfaction.