Abstract
BackgroundIn-vivo cardiovascular magnetic resonance (CMR) diffusion tensor imaging (DTI) allows imaging of alterations of cardiac fiber architecture in diseased hearts. Cardiac amyloidosis (CA) causes myocardial infiltration of misfolded proteins with unknown consequences for myocardial microstructure. This study applied CMR DTI in CA to assess microstructural alterations and their consequences for myocardial function compared to healthy controls.MethodsTen patients with CA (8 AL, 2 ATTR) and ten healthy controls were studied using a diffusion-weighed second-order motion-compensated spin-echo sequence at 1.5 T. Additionally, left ventricular morphology, ejection fraction, strain and native T1 values were obtained in all subjects. In CA patients, T1 mapping was repeated after the administration of gadolinium for extracellular volume fraction (ECV) calculation. CMR DTI analysis was performed to yield the scalar diffusion metrics mean diffusivity (MD) and fractional anisotropy (FA) as well as the characteristics of myofiber orientation including helix, transverse and E2A sheet angle (HA, TA, E2A).ResultsMD and FA were found to be significantly different between CA patients and healthy controls (MD 1.77 ± 0.17 10− 3 vs 1.41 ± 0.07 10− 3 mm2/s, p < 0.001; FA 0.25 ± 0.04 vs 0.35 ± 0.03, p < 0.001). MD demonstrated an excellent correlation with native T1 (r = 0.908, p < 0.001) while FA showed a significant correlation with ECV in the CA population (r = − 0.851, p < 0.002). HA exhibited a more circumferential orientation of myofibers in CA patients, in conjunction with a higher TA standard deviation and a higher absolute E2A sheet angle. The transmural HA slope was found to be strongly correlated with the global longitudinal strain (r = 0.921, p < 0.001).ConclusionCMR DTI reveals significant alterations of scalar diffusion metrics in CA patients versus healthy controls. Elevated MD and lower FA values indicate myocardial disarray with higher diffusion in CA that correlates well with native T1 and ECV measures. In CA patients, CMR DTI showed pronounced circumferential orientation of the myofibers, which may provide the rationale for the reduction of global longitudinal strain that occurs in amyloidosis patients. Accordingly, CMR DTI captures specific features of amyloid infiltration, which provides a deeper understanding of the microstructural consequences of CA.
Highlights
Amyloidosis is a multi-system disease that is caused by the synthesis and accumulation of unstable and misfolded proteins leading to a loss of normal tissue architecture and function [1]
While global longitudinal strain (GLS) was significantly impaired in Cardiac amyloidosis (CA) patients (− 16.6 ± 3.3 vs − 22.4 ± 1.9%, p < 0.001), global circumferential strain (GCS) (− 26.9 ± 5.5 vs − 29.1 ± 3.1%, p = 0.30) and LV ejection fraction (LVEF) (64 ± 6 vs 61 ± 4%, p = 0.20) exhibited no significant difference between the groups
The existence of a tight functional relation between fractional anisotropy (FA) and extracellular volume (ECV) is suggestive from a microstructural perspective, since the scalar cardiovascular magnetic resonance (CMR) diffusion tensor imaging (DTI) parameters describe the range and anisotropy of myocardial water movement, which is mainly determined by the tissue-specific presence of spatially ordered cellular compartments within the myocardium [32]
Summary
Amyloidosis is a multi-system disease that is caused by the synthesis and accumulation of unstable and misfolded proteins leading to a loss of normal tissue architecture and function [1]. In AL CA patients, ECV is a proven predictor of mortality with an up to four-fold increased likelihood of death for ECV > 0.45 over a median follow-up period of 23 months [10]. Both LGE and ECV, rely on the application of gadolinium-based contrast agents (GBCA), which is often limited in amyloidosis patients due to severely reduced renal function. This study applied CMR DTI in CA to assess microstructural alterations and their consequences for myocardial function compared to healthy controls
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