Multimodality Imaging in Cardiac Amyloidosis: Evidence Base and Standardized Methods of Imaging

Myocardial imaging with 99mTc-PYP/DPD/HMDP, in the appropriate clinical context, is highly sensitive and specific to diagnose ATTR cardiac amyloidosis and may aid in its early detection.

In the absence of a light-chain clone, myocardial uptake of 99mTc-PYP/DPD/HMDP of Grade ≥2 is diagnostic of ATTR cardiac amyloidosis, obviating the need for endomyocardial biopsy.

To facilitate early diagnosis of ATTR cardiac amyloidosis, cardiac 99mTc-PYP/DPD/HMDP scintigraphy should be more broadly considered in patients with unexplained increased LV wall thickness, heart failure with preserved ejection fraction, familial amyloid polyneuropathy (FAP), family history of amyloidosis, degenerative aortic stenosis with low-flow low gradient in the elderly, and a history of bilateral carpal tunnel syndrome.

¹²³I-mIBG can detect cardiac denervation in patients with hereditary ATTR amyloidosis.

Multiple imaging parameters predict a worse prognosis, including increased LV mass, lower global longitudinal strain, increased right ventricular wall thickness, higher native T1 and ECV, higher H/CL ratio, and ¹²³I-mIBG increased HMR and delayed washout rate.

Although not formally incorporated into current risk-assessment algorithms, radionuclide results should be combined with electrocardiographic, clinical, biomarker, and other imaging findings for optimal prognostication.

Transthoracic echocardiography (for the evaluation of left atrial size and function) and transesophageal echocardiography (for the evaluation of the left atrial appendage) are useful to guide initiation and management of anticoagulation in patients with cardiac amyloidosis.

Cardiovascular magnetic resonance assessment of LV wall thickness, LV mass, and particularly ECV is emerging as a tool to assess disease progression and response to therapy.

Serial SPECT ^99mTc-PYP/DPD/HMDP scintigraphy is currently not recommended to assess disease progression or response to therapy.

Transthoracic echocardiography is reasonable to monitor disease progression and/or response to therapy in cardiac amyloidosis because echocardiography is often done clinically for other reasons (ie, heart failure management).

Echocardiograms in patients with suspected or known cardiac amyloidosis should be obtained using ASE/EACVI guidelines on comprehensive echocardiography.

Reporting should include assessment of wall thickness and myocardial “texture”; thickening of other cardiac structures; pericardial effusion; tissue Doppler velocities (s', e', and a'); diastolic function; and hemodynamics.

Speckle-tracking echocardiography should be performed routinely in patients with suspected or known cardiac amyloidosis when available, and efforts should be made to optimize the apical 2D imaging views for speckle-tracking analysis. The global longitudinal strain and pattern of segmental strains (ie, ‘bullseye’ map) should be reported. RV and LA strain can be reported when performed.

An overall reporting on likelihood of amyloidosis based on imaging findings is recommended (not suggestive, strongly suggestive, or equivocal for cardiac amyloidosis).

Cardiovascular magnetic resonance should be performed using standard parameters, as listed in this section.

Cardiac structure, function, and PSIR LGE should be assessed and reported per SCMR guidelines.

Cardiac amyloidosis-specific CMR markers, such as native T1 mapping and ECV, should be assessed and reported when available, as discussed in this document.

An overall reporting on likelihood of cardiac amyloidosis based on imaging findings is recommended (eg, not suggestive, strongly suggestive, or equivocal for cardiac amyloidosis).

^99mTc-PYP/DPD/HMDP and 123I-mIBG imaging should be performed using standard protocols as discussed in this section.

SPECT imaging is useful particularly in positive or equivocal cases to differentiate myocardial from blood pool signal and to describe regional heterogeneity.

Visual and semi-quantitative interpretation of 99mTc-PYP/DPD/HMDP planar and SPECT images should be employed to evaluate heart-to-bone ratio and/or H/CL lung ratio. The HMR is used to interpret ¹²³I-mIBG images.

An overall reporting on likelihood of amyloidosis based on imaging findings is recommended (eg, not suggestive, strongly suggestive, or equivocal for cardiac amyloidosis and for extra-cardiac findings).