Multi-modality imaging of cardiac amyloidosis: Contemporary update

Table 1 Echocardiographic parameters to evaluate for cardiac amyloidosis, modified from expert consensus recommendations[5]

Parameters
Left ventricular size and ejection fraction
Left ventricular wall thickness
Myocardial echogenicity
Diastolic function
Left ventricular longitudinal strain (global and regional bull’s eye distribution)
Atrial size and function
Interatrial septum
Estimated right ventricular systolic and right atrial pressures
Valve thickness
Pericardial effusion

Table 2 Magnetic resonance imaging evaluation of cardiac amyloidosis, modified from expert consensus recommendations[5]

Protocol	Parameters
Steady state free precession cine imaging	Left ventricular size, stroke volume, ejection fraction, wall thickness, mass (without and with indexing), atrial size and function, pericardial effusion
Phase-sensitive inversion recovery for delayed contrast imaging	Late gadolinium enhancement
T1 imaging	Native T1 mapping pre-contrast, T1 inversion time scout, extracellular volume post-contrast
T2 imaging	T2 mapping, edema imaging

Table 3 Utilized acquisition parameters for ¹¹C-PiB, ¹⁸F florbetapir, and ¹⁸F florbetaben studies for cardiac amyloidosis[50-52]

Imaging considerations	Parameters
Patient and equipment preparation
Patient preparation	No prerequisites, no fasting
Position	Supine arms above shoulder or supported
Scan	Rest scan
Dose	11C-PiB 10-20 mCi (370-740 MBq) IV[50]
	18F florbetapir 6 mCi (222 MBq) IV[51]
	18F florbetaben 0.1 mCi/kg (4 MBq/kg) IV[52]
Time from injection to acquisition	11C-PiB 30 min[50]
	18F florbetapir continuous over 60 min[51]
	18F florbetaben continuous over 80 min[52]
Scan parameters
Field of view	Heart; Chest
Image type	Low-dose (10 mA, 120 kVp, free tidal breathing) CT scout scan
	Low-dose CT transmission scan (10 mA, 120 kVp, free tidal breathing) over the heart
	Emission scan 2D 40-60 mCi (1480-2220 MBq)
	Emission scan 3D 10-20 mCi (370-740 MBq)
Matrix	128 × 128-400 × 400
Reconstruction	Filtered back projection or iterative reconstruction

CT: Computed tomography.

Table 4 Contemporary diagnostic criteria for cardiac amyloidosis, modified from expert consensus recommendations[61]

Category	Criteria
Endomyocardial biopsy	Apple-green birefringence with Congo red staining and polarized light, immunohistochemistry and/or mass spectrometry typing confirmed
Extracardiac biopsy	ATTR: Biopsy proven and typical imaging findings
	AL: biopsy proven and typical imaging features or abnormal cardiac biomarkers (N-terminus B-type natriuretic peptide or troponins if other causes excluded)
Non-biopsy (or ATTR)	Grade 2 or 3 myocardial uptake of radiotracer
	Serum free light chains, serum and urine immune-fixation not finding clonal plasma cell process
	Typical imaging findings
Typical imaging findings: echocardiography	Left ventricular wall thickness > 12mm
	Relative apical sparing of left ventricular longitudinal strain ratio (apical average/basal and mid average > 1)
	Grade 2 or higher diastolic dysfunction
Typical imaging findings: magnetic resonance imaging	Left ventricular wall thickness > upper limit normal for sex
	Global extracellular volume > 0.40
	Abnormal gadolinium kinetics, myocardial nulling prior to blood pool nulling or difficulty in nulling the myocardium because of diffuse amyloid infiltration
	Diffuse, subendocardial or patchy late gadolinium enhancement patterns may be observed
Typical imaging findings: Positron emission tomography	18F-florbetapir or 18F-florbetabem
	Left ventricular myocardium to blood pool ratio > 1.5
	Retention index > 0.030/min

ATTR: Transthyretin amyloidosis; AL: Light chain amyloidosis.

Table 5 Strengths and limitations of each imaging modality for assessing cardiac amyloidosis

Modality	Echocardiography	Magnetic resonance imaging	Nuclear imaging
Strengths	Availability and portable	Lack of radiation	Distinguishing between AL/ATTR
	Low cost	High spatial resolution
	Lack of radiation	Chamber quantification
	Lack of contrast	Tissue characterization
	Chamber quantification	Quantifying myocardial fibrosis
	Diastolic function
	Strain
Weaknesses	Variable spatial resolution	Higher cost	Higher cost
	Low specificity	Availability may be limited	Availability may be limited
	No tissue characterization	Gadolinium-based contrast administration	Radiation exposure
	Not distinguish AL/ATTR	Claustrophobia
	Not able to assess and quantify myocardial fibrosis	Metallic device
		Not able to distinguish between AL/ATTR

AL: Light chain amyloidosis; ATTR: Transthyretin amyloidosis.