Cardiac MRI Monitoring of Myocardial Tissue Changes in a Myocarditis Mouse Model with Histologic Validation

Area of Science:

• Cardiovascular Imaging
• Biomedical Engineering
• Pathology

Background:

• Autoimmune myocarditis presents a diagnostic challenge in characterizing myocardial inflammation and fibrosis.
• Histopathologic assessment is invasive and lacks dynamic spatial and temporal information.
• Multiparametric cardiac MRI offers a non-invasive approach to tissue characterization.

Purpose of the Study:

• To evaluate multiparametric cardiac MRI for assessing myocardial inflammation, fibrosis, and their spatiotemporal distribution in experimental autoimmune myocarditis.
• To correlate MRI findings with histopathologic assessments of inflammation and fibrosis.
• To determine the diagnostic performance of different MRI parameters at various disease stages.

Main Methods:

• 84 BALB/c mice (42 with autoimmune myocarditis, 42 controls) underwent multiparametric cardiac MRI (T1 mapping, T2 mapping, ECV mapping) at 14 days, 28 days, and 3 months post-immunization.
• Cardiac tissues were collected for histopathologic analysis (inflammatory index, collagen volume fraction).
• MRI parameters were analyzed globally, regionally, and segmentally, with statistical comparisons and correlation analyses.

Main Results:

• Experimental autoimmune myocarditis showed progression from inflammation to fibrosis.
• T2 values were elevated early (days 14, 28) and normalized by 3 months, correlating with inflammation.
• Extracellular volume fraction (ECV) increased progressively and correlated with fibrosis, performing best at 3 months.
• T2 mapping showed high diagnostic performance for inflammation at days 14 and 28.
• Spatial distribution of abnormalities was heterogeneous and stage-dependent.

Conclusions:

• Multiparametric cardiac MRI accurately characterizes myocardial inflammation and fibrosis in autoimmune myocarditis.
• The study demonstrates stage-dependent spatial patterns of myocardial abnormalities.
• Cardiac MRI parameters provide valuable insights into the dynamic progression of autoimmune myocarditis.