Role of cardiovascular imaging for the diagnosis and prognosis of cardiac amyloidosis

Abstract

Cardiac amyloidosis (CA) describes the pathological process of amyloid protein deposition in the extracellular space of the myocardium. Unfortunately, the diagnosis of CA is often made late and when the disease process is advanced. However, advances in cardiovascular imaging have allowed for better prognostication and establishing diagnostic pathways with high sensitivity and specificity. This review discusses the role of echocardiography, cardiac MRI and nuclear cardiology in current clinical practice for diagnosis and prognosis of CA.

Keywords: cardiac amyloidosis; cardiac mri; cardio-oncology; cardiomyopathy restrictive; global longitudinal strain.

Figure 1

Diastolic function in cardiac amyloidosis (CA): diastolic parameters tend to be markedly abnormal due to stiffening of the myocardium secondary to amyloid infiltration. Aside from the classical steep deceleration time, which is consistent with restrictive diastolic dysfunction, there are other parameters that are helpful. Tissue Doppler velocity at mitral annulus (E′) are usually <6 cm/s. Also, notice the significant blunting of the systolic component of the pulmonary vein flow, suggesting high filling pressures in the absence of significant mitral regurgitation. Typically, like any other restrictive cardiomyopathy, CA will present with biatrial enlargement, reflecting the chronically elevated filling ventricular pressures.

Figure 2

Speckled pattern in transthoracic echocardiogram: with the advent of harmonic imaging, this is a feature of cardiac amyloidosis that is less reliable due to augmentation of speckles in myocardium and can be seen in harmonic imaging mode. In some echo laboratories, a frame of PLAX using fundamental imaging will be acquired on suspicion. This is a qualitative assessment and should not be used by itself to diagnose cardiac amyloidosis. LA, left atrium; LV, left ventricle; RV, right ventricle.

Figure 3

Apical ‘sparing’ pattern: This is a finding that its helpful in addition to others. The left ventricle apical contractility may be preserved quite commonly in patients with advanced cardiac amyloidosis and can be depicted in a polar map of global longitudinal strain (A). There are other causes of apical ‘sparing’ such as aortic stenosis, hypertension, hypertrophic cardiomyopathy and variant of stress-induced cardiomyopathy. Notice how the basal segments do not contract as robustly as the apex (B, C).

Figure 4

Late gadolinium enhancement in amyloidosis. Because certain artefacts regarding acquisition timing may occur when acquiring late gadolinium enhancement (LGE), the preferred technique to do LGE in amyloidosis is phase-sensitive inversion recovery (PSIR). PSIR allows to characterise better the segments that have gadolinium enhancement. The characteristic pattern is ‘global endocardial’, which also has been described as having transmural and ‘patchy’ characteristics. This case illustrated above looks mostly transmural and patchy.

Figure 5

Extracellular volume fraction in amyloidosis: T1 mapping can be used to estimate myocardial extracellular volume (ECV) fraction, a surrogate to quantify amyloid burden in extracellular space. Accurate measurement of the ECV requires a haematocrit (HCT) performed at the time of study and can be estimated using the equation above; values were taken from the region of interest–derived values, pre-contrast (native) and post-contrast T1 maps. ECV at equilibrium of greater than 0.45 has been shown to portend a poor prognosis in light-chain amyloidosis.

Figure 6

Suggested algorithm for cardiac imaging diagnosis and stratification of cardiac amyloidosis. AL, light-chain amyloidosis; ATTR, abnormal transthyretin; CMR, cardiovascular magnetic resonance; DPD, 3,3-diphosphono-1,2-propanodicarboxylic acid; ECV, extracellular volume; GLS, global longitudinal strain; PYP, pyrophosphate; SPECT, single-photon emission CT.