Diagnosis of Cardiac Involvement in Amyloid A Amyloidosis by Cardiovascular Magnetic Resonance Imaging

Abstract

Background: Diagnosis of cardiac involvement in amyloid A (AA) amyloidosis is challenging since AA amyloidosis is a rare disease and cardiac involvement even less frequent. The diagnostic yield of currently available non-invasive imaging methods is not well-studied and rather limited, and invasive endomyocardial biopsy (EMB) is rarely performed due to the potential risk of this procedure. Cardiovascular magnetic resonance (CMR)-based myocardial tissue characterization by late-gadolinium-enhancement (LGE) imaging and novel-mapping approaches may increase the diagnostic yield in AA amyloidosis. Methods: Two patients with AA amyloidosis in whom cardiac involvement was suspected based on CMR findings and subsequently proven by biopsy work-up are presented. CMR studies were performed on a 1.5-T system and comprised a cine steady-state free precession pulse sequence for ventricular function and a late-gadolinium-enhancement (LGE) sequence for detection of myocardial pathology. Moreover, a modified Look-Locker inversion recovery (MOLLI) T1-mapping sequence was applied in basal, mid and apical short-axes prior to contrast agent administration and ~20 min thereafter to determine native T1 and ECV values. Results: Both patients showed slightly dilated left ventricles (LV) with mild to moderate LV hypertrophy and preserved systolic function. Only a very subtle pattern of LGE was observed in both patients with AA amyloidosis. However, markedly elevated native T1 (max. 1,108 and 1,112 ms, respectively) and extracellular volume fraction (ECV) values (max. 39 and 48%, respectively) were measured in the myocardium suggesting the presence of cardiac involvement - with subsequent EMB-based proof of AA amyloidosis. Conclusion: We recommend a multi-parametric CMR approach in patients with AA amyloidosis comprising both LGE-based contrast-imaging and T1-mapping-based ECV measurement of the myocardium for non-invasive work-up of suspected cardiac involvement. The respective CMR findings may be used as gatekeeper for additional invasive procedures (such as EMB) and as a non-invasive monitoring tool regarding assessment and modification of ongoing treatments.

Keywords: AA amyloidosis; ECV; cardiac involvement; cardiovascular magnetic resonance (CMR); mapping—magnetic resonance imaging; serum amyloid A (SAA).

Figure 1

(A) Cardiovascular magnetic resonance (CMR) images of patient-1 showing cine images in diastole and systole as well as corresponding late-gadolinium-enhancement (LGE) and extracellular volume fraction (ECV) maps of the myocardium. A very subtle and rather diffuse pattern of LGE was detected in the basal segments of the LV lateral wall. However, ECV maps illustrated highly elevated myocardial ECV values in the septal and lateral wall segments. (B) Histopathological images of endomyocardial biopsy (EMB) samples that were taken in patient-1 from the left ventricular free wall. Congo-red staining showed a diffuse pattern of interstitial amyloidosis (red arrows) in addition to marked accumulation of amyloid deposits within the vessel walls (blue arrows). The subtype AA amyloidosis was proven by specific immunohistochemistry.

Figure 2

Cardiovascular magnetic resonance (CMR) images of patient-2 showing cine images in diastole and systole as well as corresponding late-gadolinium-enhancement (LGE) and extracellular volume fraction (ECV) maps of the myocardium. A slightly more pronounced non-ischemic pattern of LGE was observed in this patient in the basal to midventricular inferior/inferolateral segments of the LV wall (red arrows). Again, ECV maps illustrated highly elevated myocardial ECV values in the septal and lateral wall segments.