ST-Elevation Myocardial Infarction

ST-elevation myocardial infarction (STEMI) is the acute coronary syndrome subtype defined by persistent ST-segment elevation on the electrocardiogram, reflecting acute, usually complete, occlusion of a coronary artery with ongoing myocardial necrosis. It is the most time-critical presentation in the chest pain spectrum because the extent of myocardial damage depends heavily on how quickly coronary flow is restored.

Definition

ST-elevation myocardial infarction is acute myocardial infarction characterised by new, persistent ST-segment elevation meeting lead-specific electrocardiographic criteria, typically caused by acute total or near-total occlusion of an epicardial coronary artery.

Scope

This topic defines STEMI, its pathophysiology and electrocardiographic diagnosis, and the central principle that timely reperfusion limits infarct size. It is framed as a reference and educational entry; it describes the concepts and evidence behind STEMI care, including the rationale for minimising time to reperfusion, without prescribing specific drugs, doses, or procedures for an individual patient.

Core questions

• What distinguishes STEMI from other acute coronary syndromes?
• How is STEMI recognised on the electrocardiogram?
• Why is time to reperfusion central to STEMI outcomes?
• How does STEMI fit within the universal definition of myocardial infarction?

Key concepts

• Persistent ST-segment elevation
• Acute total coronary occlusion
• Transmural myocardial necrosis
• Reperfusion and time-dependent myocardial salvage
• Door-to-balloon and system-of-care metrics
• STEMI-equivalent electrocardiographic patterns

Mechanisms

STEMI typically results from rupture or erosion of an atherosclerotic plaque with formation of an occlusive thrombus that abruptly interrupts blood flow through an epicardial coronary artery. The resulting transmural ischaemia produces the characteristic ST-segment elevation and, if flow is not restored, a wavefront of myocyte necrosis that progresses from the subendocardium outward over time. Because viable myocardium is lost as ischaemia continues, the clinical emphasis is on prompt restoration of coronary perfusion to salvage myocardium (Byrne et al., 2023; Thygesen et al., 2018).

Clinical relevance

STEMI is the presentation in which the relationship between elapsed time and myocardial loss is most direct, which is why systems of care are organised to recognise it rapidly and shorten the interval to reperfusion. The concepts described here, including time-to-treatment metrics, explain how the evidence base informs STEMI care at a system level; they are educational and not individualised treatment instructions.

Epidemiology

STEMI represents a substantial share of acute myocardial infarctions and carries high early mortality if reperfusion is delayed. Observational evidence has linked shorter treatment times to lower mortality, supporting the system-level focus on rapid reperfusion (Rathore et al., 2009).

Evidence & guidelines

The 2023 ESC acute coronary syndromes guideline (Byrne et al., 2023) sets out the contemporary framework for recognising and reperfusing STEMI, and the Fourth Universal Definition of Myocardial Infarction (Thygesen et al., 2018) provides the diagnostic criteria. Standardised electrocardiographic criteria for acute ischaemia and infarction (Wagner et al., 2009) underpin the diagnosis, and registry analyses such as Rathore et al. (2009) document the prognostic importance of timely reperfusion.

History

Recognition that STEMI reflects acute coronary occlusion, and that reopening the artery limits infarct size, reshaped its management over recent decades, shifting emphasis toward rapid reperfusion and the measurement of treatment delays. Standardised electrocardiographic definitions (Wagner et al., 2009) and successive universal definitions of myocardial infarction (Thygesen et al., 2018) refined how the diagnosis is made, while large registries (Rathore et al., 2009) quantified the value of speed.

Seminal works

• thygesen-2018
• byrne-2023
• rathore-2009

Frequently asked questions

What does ST elevation on the electrocardiogram indicate in STEMI?

Persistent ST-segment elevation meeting lead-specific criteria reflects acute, usually complete, coronary occlusion with transmural ischaemia and ongoing myocyte necrosis, which is the defining feature of STEMI.

Why is time so important in STEMI?

Because myocardial necrosis progresses while the artery remains occluded, the amount of muscle that can be salvaged falls as time passes, which is why systems of care aim to minimise the interval to reperfusion.