Characterizing cardiac involvement in amyloidosis using cardiovascular magnetic resonance diffusion tensor imaging

Area of Science:

• Cardiovascular Imaging
• Cardiac Electrophysiology
• Biomedical Engineering

Background:

• Cardiac amyloidosis (CA) involves myocardial infiltration by misfolded proteins, leading to unknown microstructural consequences.
• In-vivo cardiovascular magnetic resonance (CMR) diffusion tensor imaging (DTI) is a technique to visualize cardiac fiber architecture in diseased hearts.
• Understanding CA's impact on myocardial microstructure is crucial for assessing functional consequences.

Purpose of the Study:

• To apply CMR DTI in patients with CA to assess microstructural alterations.
• To compare these microstructural alterations with those in healthy controls.
• To investigate the consequences of these microstructural changes on myocardial function.

Main Methods:

• Ten CA patients (8 AL, 2 ATTR) and ten healthy controls underwent CMR using a diffusion-weighted spin-echo sequence at 1.5T.
• Standard CMR sequences assessed left ventricular morphology, ejection fraction, strain, and native T1 values.
• CMR DTI analysis yielded scalar diffusion metrics (mean diffusivity [MD], fractional anisotropy [FA]) and myofiber orientation characteristics (helix angle [HA], transverse angle [TA], E2A sheet angle).

Main Results:

• Significant differences in MD and FA were observed between CA patients and controls (p < 0.001).
• Elevated MD correlated with native T1 values (r=0.908, p < 0.001), and reduced FA correlated with extracellular volume fraction (ECV) (r=-0.851, p < 0.002) in CA patients.
• CA patients exhibited altered myofiber orientation (circumferential HA, increased TA standard deviation, higher absolute E2A) and a strong correlation between transmural HA slope and global longitudinal strain (r=0.921, p < 0.001).

Conclusions:

• CMR DTI effectively detects significant microstructural alterations in CA, characterized by increased MD and decreased FA, correlating with T1 and ECV measures.
• The observed pronounced circumferential myofiber orientation in CA patients provides a potential explanation for reduced global longitudinal strain.
• CMR DTI offers valuable insights into the specific microstructural changes induced by amyloid infiltration in CA, enhancing understanding of disease pathophysiology.