Introduction Cardiac amyloidosis is a disease of infiltration, typically by light chains (AL) or transthyretin (ATTR). We studied cardiac amyloidosis using diffusion tensor cardiovascular magnetic resonance (DT-CMR), which is the only non-invasive tool able to assess cardiac microstructure in-vivo.
Methods and results Biphasic STEAM DT-CMR was successfully performed in 20 cardiac amyloidosis patients (10 AL, 10 ATTR) and 10 age and sex matched controls. Compared with controls, amyloid patients had higher mean diffusivity (MD); median [IQR] 1.46 [1.36–1.54] × 10−3 mm2/s vs 1.15 [1.03–1.20] × 10−3 mm2/s (p<0.001), shown in figure 1A. MD correlated with T1 (R2=0.76, p<0.001) and extracellular volume (ECV) (R2=0.47, p=0.004).
Amyloid patients had lower fractional anisotropy (FA) compared to controls; 0.43 [0.39–0.45] vs (0.55 [0.52–0.60], p<0.001), as shown in figure 1B. FA inversely correlated with T1 (R2=0.59, p<0.001). Amyloid patients had elevated diastolic E2A and reduced E2A mobility (both <0.001).
Segmental analysis for co-location of FA and MD with ECV amyloid infiltration showed good correlation (both p<0.001). Example maps are shown in figure 2. There was no significant difference in MD, FA or E2A mobility between amyloid subtypes.
Conclusion In cardiac amyloidosis, DT-CMR characterises the microstructural effects of infiltration, and increases in MD show good correlation with increases in ECV. The novel insights from DT-CMR offer a deeper understanding of pathophysiological mechanisms in cardiac amyloidosis. With further development, DT-0CMR might offer a gadolinium free assessment of amyloid burden, which is of particular value in renal failure.
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