Background: A significant proportion of patients with ST-elevation myocardial infarction (STEMI) have a preserved left ventricular ejection fraction (LVEF) soon after the acute event, yet, it is largely unknown how to risk stratify them.

Objectives: To assess the prognostic value of clinical and cardiac magnetic resonance (CMR) risk markers in a large STEMI population with preserved LVEF following primary percutaneous coronary intervention (PCI).

Methods: This multicenter, individual patient-data analysis from two large CMR trials included 1247 STEMI patients. CMR examinations were conducted 3 (interquartile range[IQR]:2-4) days after PCI. LVEF, infarct size, microvascular obstruction (MVO) and LV strain values were measured. Primary endpoint was a composite of major adverse cardiovascular events (MACE) including death, re-infarction and congestive heart failure.

Results: A preserved LVEF (≥50%) was observed in 724 patients (58%). In total, 97 patients experienced a MACE event, 34 MACE events (35%) occurred in the group with preserved LVEF. TIMI risk score (hazard ratio[HR]:1.28[95%CI:1.02-1.59];p=0.03) and female gender (HR:2.24[95%CI:1.10-4.57];p=0.03) emerged as independent clinical determinants of MACE in the preserved LVEF group. Among CMR parameters, presence of MVO (HR:2.19[95%CI:1.02-4.75];p=0.04) and global longitudinal strain (GLS; HR:1.15[95%CI:1.04-1.28];p=0.01) independently predicted MACE in the preserved LVEF population. The addition of MVO and GLS to the clinical prognostic markers (TIMI risk score and female gender) increased (p=0.02) the prognostic validity (AUC:0.76[95%CI:0.73-0.79]) as compared to the clinical markers alone (AUC:0.65[0.62-0.69]).

Conclusions: In contemporary treated STEMI patients showing preserved LVEF, a CMR-based risk prediction approach assessing MVO and GLS provided strong prognostic value that was incremental to clinical outcome parameters.