Myocardial fat deposition in patients with chronic myocardial infarction: detection by using magnetic resonance fat-water separation and feature tracking imaging

Background: Excessive lipid accumulation within the myocardial tissue predisposes to ventricular arrhythmias and increased risk of sudden cardiac death. This study aimed to detect intramyocardial fat infiltration in patients with chronic myocardial infarction (MI) using advanced cardiac magnetic resonance (CMR) imaging techniques – fat-water separation and feature tracking. Methods: Twenty patients with chronic MI underwent advanced CMR imaging. The study protocol included conventional cine, late gadolinium enhancement (LGE) and fat-water separation (2-point mDixon) imaging. Left ventricular (LV) circumferential (EccLV) and radial (ErrLV) strain were calculated using dedicated software (CMR42, Calgary, Canada). The extent of global scar tissue was calculated in LGE and fat-water separation images to compare advanced and conventional imaging techniques. Results: The infarct size as derived from conventional LGE and fat-water separation images was similar. However, detection of intramyocardial fat was only possible with fat-water separation imaging. Subjects with intramyocardial fat deposition demonstrated significantly smaller percentage of fibrosis than those without fat deposition (10.68 ± 5.07 % vs. 13.83 ± 6.30 %; p = 0.005). There was no significant difference in LV circumferential (EccLV) and radial (ErrLV) strain between myocardial segments containing fibrosis only and fibrosis with fat deposition (-11.94 ± 5.92 % vs. -12.63 ± 7.14 %; p = 0.668 for EccLV and 20.85 ± 16.48 % vs. 17.89 ± 12.43 %; p = 0.607 for ErrLV). Conclusions: Advanced CMR imaging enables more detailed tissue characterization in patients with previous MI without relevant increase in examination or post-processing time. LGE and myocardial feature tracking techniques are unable to detect intramyocardial fat deposition.