Quantitative intramyocardial hemorrhage assessment by conventional T2-weighted imaging improves risk stratification in reperfused STEMI.

Intramyocardial hemorrhage (IMH), a severe reperfusion injury, is optimally detected by T2* mapping, which remains limited by sensitivity to artifacts and relatively long acquisition times. We aimed to evaluate the prognostic value of IMH identified by conventional T2-weighted (T2W) imaging in patients with ST-elevation myocardial infarction (STEMI). In this single-center retrospective study, 453 STEMI patients underwent CMR at a median of 5 days post-reperfusion. IMH was identified quantitatively as a hypointense core within edema on T2W imaging and expressed as a percentage of left ventricular mass. The primary endpoint was a composite of all-cause death and heart failure hospitalization. IMH was present in 167 patients (36.9%). Over a median follow-up of 25 months, 49 patients (10.8%) experienced MACE. Those with MACE had a higher prevalence of IMH (75.5% vs. 32.2%, p < 0.001). Multivariable Cox regression identified IMH extent ≥ 1.0% of LV mass as a strong and independent predictor of MACE (HR 1.14, 95% CI 1.07-1.21, p < 0.001). Adding quantitative IMH to a base model (anterior infarction, IS, MVO, LVEF) significantly improved prognostic performance: AUC increased from 0.800 to 0.828, with net reclassification improvement of 12% (p < 0.001) and integrated discrimination improvement of 7% (p = 0.018). In this selected cohort, quantitative IMH assessment using conventional T2W imaging provides significant incremental prognostic value beyond traditional risk factors in STEMI patients, enabling improved risk stratification with a widely available CMR sequence.