Diagnosis of ATTR cardiac amyloidosis by 99mTc-PYP scintigraphy: case series.

Objectives: Tc-PYP scintigraphy in a Peruvian hospital. Materials and Methods: Tc-PYP, planar imaging, and SPECT acquisition at 1 and 3 hours. Noninvasive diagnosis was established in the presence of visual myocardial uptake grade 2-3 (Perugini scale), confirmed by SPECT and after the exclusion of monoclonal plasma cell dyscrasia. The heart-to-contralateral lung (H/CL) ratio was used as a complementary quantitative parameter. Results: The average age was 69.7±10.3 years; 66.7% were male. All patients had left ventricular hypertrophy and 83.3% had heart failure. Three patients (50%) showed grade 2-3 uptake; among them, two (33.3%) met criteria for noninvasive ATTR diagnosis (grade 3, positive SPECT, and negative monoclonal screening), with H/CL values above diagnostic cutoffs. One grade 2 case had an IgG kappa monoclonal component and was classified as inconclusive. Three patients (50%) had grade 1 uptake, considered equivocal, with H/CL values below diagnostic thresholds. SPECT was essential to confirm true myocardial uptake and avoid overinterpretation in borderline cases. Conclusions: Tc-PYP is feasible in our setting and allows for appropriate classification of patients with suspected ATTR.