Visualization of post-STEMI myocardial infarction and microvascular obstruction with non-contrast, free-breathing...

Clinical adoption of cardiovascular magnetic resonance (CMR) for risk stratification in ST-elevation myocardial infarction (STEMI) is often limited by long scan times and the requirement for breath-holding and contrast agents.

This study aimed to validate a non-contrast, free-breathing 3D whole-heart T1/T2 CMR method (iT₂prep-IR BOOST) for rapid assessment of myocardial injury in STEMI patients, hypothesizing that this technique provides promising diagnostic accuracy and quantitative assessment to conventional contrast-enhanced CMR.

A free-breathing 3D isotropic whole-heart iT₂prep-IR BOOST sequence was performed with a scan time of <8minutes. Sixty-four STEMI patients underwent CMR, including iT₂prep-IR BOOST, clinical T2-STIR, late gadolinium enhancement (LGE) and T1/T2 mapping. The diagnostic performance of iT₂prep-IR BOOST was evaluated against LGE and T2-STIR to assess myocardial infarction (MI), microvascular obstruction (MVO), and edema. Subgroup analyses further investigated the association between MVO detected by iT₂prep-IR BOOST and left ventricular (LV) remodeling at 1-year follow-up.

In 60 STEMI patients, the acquisition was completed in 7.2 ± 0.6min as a single free-breathing 3D whole-heart scan. Patient-level analysis showed high sensitivity and specificity for MVO (100.0% / 87.5%) and segmental MVO detection (95.8% / 97.8%). T₂prep-IR BOOST yielded robust image contrast for MI comparable to LGE, while offering comparable edema visualization to T2-STIR. Volumetric and transmurality quantifications of MVO, MI, and edema showed excellent agreement with reference standards (all r > 0.90, p < 0.001), supported by significant biophysical correlations with native T1/T2 values (p < 0.001). Furthermore, in a 1-year follow-up cohort (n=51), baseline T₂prep-IR BOOST-derived MVO volume was associated with adverse left ventricular remodeling, showing significant correlations with both ΔLVEDVI (r = 0.305, p = 0.029) and ΔLVESVI (r = 0.293, p = 0.037).

In this preliminary single-center study, iT₂prep-IR BOOST showed promising diagnostic performance and close quantitative agreement with conventional LGE and T2-STIR in stable STEMI patients. Further prospective validation in larger, independent, and more heterogeneous cohorts, including patients unable to undergo contrast-enhanced CMR, is required before this technique can be considered an alternative to standard LGE and T2-weighted sequences.