Native T₁ Mapping by 3-T CMR Imaging for Characterization of Chronic Myocardial Infarctions

Objectives The purpose of this study was to investigate whether native T₁ maps at 3-T can reliably characterize chronic myocardial infarctions (MIs) in patients with prior ST-segment elevation myocardial infarction (STEMI) or non-ST-segment elevation myocardial infarction (NSTEMI). Background Late gadolinium enhancement (LGE) cardiac magnetic resonance is the gold standard for characterizing chronic MIs, but it is contraindicated in patients with end-stage chronic kidney disease. Methods Native T₁ and LGE images were acquired at 3-T in patients with prior STEMI (n = 13) and NSTEMI (n = 12) at a median of 13.6 years post-MI. Infarct location, size, and transmurality were measured using mean ± 5 SDs thresholding criterion from LGE images and T₁ maps and compared against one another. Independent reviewers assessed visual conspicuity of MIs on LGE images and T₁ maps. Results Native T₁ maps and LGE images were not different for measuring infarct size (STEMI: p = 0.46; NSTEMI: p = 0.27) and transmurality (STEMI: p = 0.13; NSTEMI: p = 0.21) using thresholding criterion. Using thresholding criterion, good agreement was observed between LGE images and T₁ maps for measuring infarct size (STEMI: bias = 0.6 ± 3.1%; R² = 0.93; NSTEMI: bias = -0.4 ± 4.4%; R² = 0.85) and transmurality (STEMI: bias = 2.0 ± 4.2%; R² = 0.89; NSTEMI: bias = -2.7 ± 7.9%; R² = 0.68). Sensitivity and specificity of T₁ maps for detecting chronic MIs based on thresholding criterion were 89% and 98%, respectively (STEMI), and 87% and 95%, respectively (NSTEMI). Relative to LGE images, the mean visual conspicuity score for detecting chronic MIs was significantly lower for T₁ maps (p < 0.001 for both cases). Median infarct-to-remote myocardium contrast-to-noise ratio was 2.5-fold higher for LGE images relative to T₁ maps (p < 0.001). Sensitivity and specificity of T₁ maps for visual detection were 60% and 86%, respectively (STEMI), and 64% and 91% (NSTEMI), respectively. Conclusions Chronic MIs in STEMI and NSTEMI patients can be reliably characterized using threshold-based detection on native T₁ maps at 3-T. Visual detection of chronic MIs on native T₁ maps in both patient populations has high specificity, but modest sensitivity.