What imaging modalities are needed to diagnose amyloidosis?

From the Guidelines

Imaging for diagnosing amyloidosis should include a combination of echocardiography, cardiac MRI, and nuclear scintigraphy, with the specific modality depending on the suspected type and organ involvement, as recommended by the 2021 expert consensus guidelines 1. When diagnosing cardiac amyloidosis, echocardiography is often the first imaging test, showing increased ventricular wall thickness and a characteristic "speckled" myocardial appearance.

• Key echocardiography findings include:
  • LV wall thickness > 12 mm
  • Relative apical sparing of global LS ratio
  • ≥ Grade 2 diastolic dysfunction Cardiac MRI with gadolinium contrast provides excellent tissue characterization, with late gadolinium enhancement in a subendocardial or transmural pattern being highly suggestive of cardiac amyloidosis.
• Key cardiac MRI findings include:
  • LV wall thickness > ULN for sex
  • Global ECV > 0.40
  • Diffuse LGE Nuclear scintigraphy using tracers like technetium-99m pyrophosphate (99mTc-PYP) is particularly useful for diagnosing transthyretin (ATTR) cardiac amyloidosis, with strong myocardial uptake being diagnostic when combined with absence of monoclonal proteins, as supported by the 2019 expert consensus recommendations 1.
• Key nuclear scintigraphy findings include:
  • 99mTc-PYP, DPD, HMDP Grade 2 or 3 myocardial uptake of radiotracer
  • Absence of a clonal plasma cell process as assessed by serum FLCs and serum and urine immunofixation While these imaging techniques are valuable, definitive diagnosis typically requires tissue biopsy with Congo red staining to confirm amyloid deposits, followed by mass spectrometry or immunohistochemistry to determine the specific amyloid type, as recommended by the 2021 expert consensus guidelines 1.

From the Research

Imaging Techniques for Diagnosing Amyloidosis

• Echocardiography can provide significant evidence for the diagnosis of cardiac amyloidosis 2
• Cardiac Magnetic Resonance (CMR) is useful for diagnosing cardiac amyloidosis, especially when echocardiography results are inconclusive 2, 3
• Nuclear medicine techniques, such as bone scintigraphy, can help diagnose the transthyretin (ATTR) amyloidosis subtype 4, 3
• CMR provides a comprehensive evaluation of morphological and functional abnormalities, inversion time, late gadolinium enhancement, and can include advanced techniques such as T1 mapping and extracellular volume quantification for diagnostic and prognostic purposes 3

Diagnostic Algorithm

• A non-invasive algorithm can be used to diagnose cardiac amyloidosis, which includes cardiac scintigraphy and monoclonal protein assessment 2
• If the imaging results are negative but the clinical suspicion remains high, a myocardial biopsy should be performed 2
• In the case of the presence of monoclonal protein, an invasive algorithm follows, first by surrogate site sampling and then by myocardial biopsy if the results are inconclusive or prompt diagnosis is needed 2

Importance of Imaging in Diagnosis

• Imaging techniques, such as CMR and nuclear medicine, play a pivotal role in the non-invasive diagnosis of cardiac amyloidosis 3
• A high index of suspicion is paramount in making the correct diagnosis, and imaging techniques can help establish the diagnosis of cardiac amyloidosis 4
• Timely diagnosis of cardiac amyloidosis is crucial, and imaging techniques can help achieve this goal 4, 5