Comparison of cardio-focal and chest reconstruction of technetium-99m pyrophosphate scintigraphy for diagnosis of transthyretin cardiac amyloidosis: a quality assurance study.

BACKGROUND

SPECT improves diagnostic specificity of Technetium-99m pyrophosphate (PYP) scintigraphy. Diagnostic performance of PYP data, reconstructed as either chest or cardio-focal SPECT is not known.

METHODS

In this quality assurance study, blinded evaluation of PYP SPECT/CT data from 102 Caucasian patients (mean age 76 ± 11 years, 67% men) was performed by two readers. Reader 1 reviewed planar and PYP chest SPECT, while reader 2 reviewed planar and cardio-focal PYP SPECT. Demographic, clinical, and other testing data were obtained from the electronic medical records.

RESULTS

A total of 41 patients (40%) were considered positive based on myocardial uptake on chest PYP SPECT. Of these, 98% of the patients had a Perugini score ≥ 2 on planar imaging. There was good agreement between the two readers for visual score ≥ 2 (k = .88, P < .001) and excellent agreement for myocardial uptake on tomographic imaging (98%, P < .001). Only one study was categorized as false negative by cardio-focal SPECT reconstruction. Non-diffuse myocardial uptake was identified in 22% of those with a positive PYP SPECT.

CONCLUSION

When read by experienced readers, chest and cardio-focal reconstruction of PYP SPECT have comparable diagnostic performance. A substantial proportion of patients with a positive PYP SPECT have a non-diffuse distribution of PYP. Given the possibility of misclassification of non-diffuse myocardial uptake on cardio-focal reconstruction alone, chest reconstruction of PYP scintigraphy should be strongly considered.