OBJECIVE - There is a paucity of studies investigating the impact of mid-range ejection fraction (mrEF) on clinical outcomes, including ventricular arrhythmias, in ST-segment-elevation myocardial infarction (STEMI). We sought to investigate the prognostic role of mrEF post STEMI and whether recommended medical therapy may modify future risk.

METHODS - 533 consecutive patients from a single large-volume centre who underwent primary percutaneous coronary intervention were included. Reduced EF (<40%), mrEF (40-49%) and preserved EF (≥50%) were defined according to the European Society of Cardiology guidelines. Clinical outcomes were prospectively collected, and the primary endpoint was defined as the composite of death, re-admission with heart failure, sustained ventricular arrhythmia requiring hospitalisation or implantable cardioverter defibrillator over three years follow-up.

RESULTS - There was a stepwise increase in the primary endpoint according to EF group (8%, 17%, 30%, P < .001), which was derived from each individual component. Compared to preserved EF, patients with mrEF had significantly higher risk [HR 4.08 (95%CI 2.38 to 6.99), P < .001]. The use of suboptimal medical therapy was associated with increased future risk, particularly in mrEF [HR 2.62, (95%CI 1.18 to 5.83), P = .018]. The proportion of mrEF patients who experience the primary endpoint was significantly different according the status of kidney function and recommended medical therapy (8%, 20%, 33%, 50%, P < .001).

CONCLUSIONS - Patients presenting with mrEF following STEMI had increased risk of death, heart failure hospitalisation and ventricular arrhythmias compared to preserved EF. Suboptimal medical therapy in mrEF was associated with increased adverse events, particularly in patients with renal dysfunction.