Late-presenting ST-segment elevation myocardial infarction: is it just a matter of time? From temporal cutoffs to biological staging.

Late presentation in ST-segment elevation myocardial infarction (STEMI) remains common and clinically challenging, as the duration of myocardial ischemia has traditionally been considered the main determinant of infarct size. However, the conventional 12-hour cut-off, derived from fibrinolytic-era evidence, no longer fully reflects contemporary understanding of ischemia pathophysiology, advances in percutaneous coronary intervention (PCI), and the ability to assess residual myocardial viability. The optimal management of late-presenting STEMI therefore remains debated, as reflected by divergent international guideline recommendations and the heterogeneity of available randomized clinical trials. While early studies failed to demonstrate a clear benefit of late reperfusion, more recent observational and imaging-based data suggest that selected patients may still experience myocardial salvage and improved outcomes even when revascularization is performed beyond traditional temporal thresholds. Collectively, these observations indicate that time from symptom onset represents an imprecise surrogate of myocardial infarct evolution. Focusing exclusively on symptom duration oversimplifies a complex pathophysiological process and risks denying reperfusion to patients who may still derive meaningful benefit. This state-of-the-art review critically appraises current evidence on late-presenting STEMI and proposes a physiology- and imaging-guided framework that integrates clinical presentation, electrocardiographic dynamics, biomarker kinetics, and cardiac imaging to support biologically informed decision-making beyond rigid time-based cut-off.