# Cardiac amyloidosis (transthyretin, ATTR-CM)

Source: https://nuclide.cc/indications/cardiac-amyloidosis-attr/  
Nuclide record `cardiac-amyloidosis-attr` (Indication). Data CC BY-NC 4.0, attribute "Data from Nuclide (nuclide.cc)"; commercial use needs a licence.

## TL;DR

A misfolded blood protein called transthyretin builds up as stiff deposits inside the heart muscle, making it thicken and stop relaxing properly. A bone-scanning tracer that also sticks to these deposits can diagnose it without a heart biopsy.

## Summary

Transthyretin amyloid cardiomyopathy (ATTR-CM) is caused by misfolded transthyretin (wild-type or a hereditary variant) depositing as amyloid fibrils in the myocardium, producing a restrictive, thick-walled heart failure phenotype that mimics hypertensive heart disease on echocardiography. It is distinct from AL (light-chain) cardiac amyloidosis, which needs haematology-led treatment, so excluding a plasma cell clone (serum/urine immunofixation and free light chains) alongside imaging is mandatory.

Bone-avid Tc-99m bisphosphonate tracers (pyrophosphate, or DPD/HMDP outside the US) bind ATTR amyloid deposits, apparently via calcium co-deposition, and are read against rib (bone) uptake on a 0-3 visual grade. Gillmore et al. (2016, JAMA Cardiology, n=1,217) showed grade 2-3 uptake, combined with the absence of a monoclonal protein, had 100% specificity and positive predictive value for ATTR-CM, avoiding endomyocardial biopsy in most patients. Multisociety expert consensus (ASNC/AHA/ASE/EANM/HFSA/ISA/SCMR/SNMMI, with a 2021 addendum) now requires SPECT or SPECT/CT confirmation of myocardial uptake; planar grading or the heart-to-contralateral ratio alone is no longer sufficient for diagnosis.

The test matters clinically because ATTR-specific therapies (TTR stabilisers and gene-silencing agents) are now available, so a confident non-invasive diagnosis changes management; this is outside Nuclide's therapeutic scope but is the reason demand for pyrophosphate scanning has grown sharply since the mid-2010s.

## Fields

- Kind: Indication
- Last checked: 2026-09-22
- Group: cardiology

## Standard of care

- non-invasive diagnosis of ATTR-CM: Tc-99m pyrophosphate (or DPD/HMDP) SPECT/CT grade 2-3 myocardial uptake plus exclusion of a monoclonal light-chain clone ([Technetium Tc-99m pyrophosphate](https://nuclide.cc/drugs/tc-99m-pyrophosphate/))

## Sources

- Gillmore et al. 2016, JAMA Cardiology: Tc-99m PYP scintigraphy for ATTR cardiac amyloidosis: https://jamanetwork.com/journals/jamacardiology/fullarticle/2546034
- ASNC practice points: 99mTc-pyrophosphate imaging for cardiac amyloidosis: https://www.asnc.org/wp-content/uploads/2024/05/ASNC-Practice-Point-99mTechnetium-Pyrophosphate.2016.pdf

## Connected records

- drugs: [Technetium Tc-99m pyrophosphate](https://nuclide.cc/drugs/tc-99m-pyrophosphate/)
- isotopes: [Technetium-99m](https://nuclide.cc/isotopes/tc-99m/)
- institutions: [American Society of Nuclear Cardiology](https://nuclide.cc/institutions/asnc/)

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