Cardiac PYP Interpreter (ATTR)
Heart-to-contralateral ratio and Perugini grade for transthyretin cardiac amyloid
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Enter the heart and contralateral-chest ROI counts and the imaging timepoint to compute the heart-to-contralateral (H/CL) ratio, and select the Perugini visual grade. The tool returns the standard interpretation — with the mandatory reminder that a positive scan diagnoses ATTR only after a monoclonal protein has been excluded (see Cardiac Amyloidosis).
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Heart-to-contralateral (H/CL) ratio
Mandatory: a positive scan diagnoses ATTR only after a monoclonal protein is excluded (serum/urine immunofixation + free light chains). SPECT is required to confirm uptake is myocardial, not blood pool or bone.
Evidence & sources
BMultisociety PYP practice points — H/CL ratio thresholds (≥1.5 at 1 h) and Perugini grading; monoclonal-protein exclusion required.
BGillmore JD, et al. Circulation 2016 — grade 2–3 with negative monoclonal screen is highly specific for ATTR.