Native T₁ mapping for characterization of acute and chronic myocardial infarction in swine: Comparison with contrast-enhanced MRI

Background: Both acute and chronic myocardial infarction (AMI and CMI, respectively) exhibit delayed enhancement; however, clinical decision-making processes frequently require the differentiation of these two types of myocardial injury.

Purpose: To investigate the reliability of AMI and CMI characterization using native T₁ mapping and its feasibility for discriminating AMI from CMI.

Study type: Case-control.

Animal model: The study cohort comprised 12 AMI (mean post-MI, 3.75 ± 1.29 days) and 15 CMI (mean post-MI, 39.53 ± 6.10 days) Bama mini-pigs.

Field strength/sequence: Balanced steady-state free precession (bSSFP), segmented-turbo-FLASH-PSIR, and modified Look-Locker inversion recovery (MOLLI) sequences at 3.0T.

Assessment: The infarct sizes were compared on matching short-axis slices of late-gadolinium-enhanced (LGE) images and T₁ maps by two experienced radiologists.

Statistical tests: The infarct sizes were compared on matching short-axis slices of LGE images and T₁ maps, and agreement was determined using linear regression and Bland-Altman analyses. The native T₁ values were compared between AMI and CMI models (independent sample t-test). The intraclass correlation coefficient was used to assess inter- and intraobserver variability.

Results: Measured infarct sizes did not differ between native T₁ mapping and LGE images (AMI: P = 0.913; CMI: P = 0.233), and good agreement was observed between the two techniques (AMI: bias, -3.38 ± 19.38%; R² = 0.96; CMI: bias, -10.55 ± 10.90%; R² = 0.90). However, the native infarction myocardium T₁ values and the T₁ signal intensity ratio of infarct and remote myocardium (T₁ SI ratio) did not differ significantly between AMI and CMI (P = 0.173).

Data conclusion: Noncontrast native T₁ mapping can accurately determine acute and chronic infarct areas as well as conventional LGE imaging; however, it cannot distinguish acute from chronic MI.

Level of evidence: 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:1406-1414.