Cardiovascular

ST-Elevation Myocardial Infarction (STEMI)

ST-elevation myocardial infarction (STEMI) is acute coronary occlusion, usually thrombus on a disrupted plaque, whose injury current appears as persistent regional ST elevation in a compatible ischaemic presentation.

Definition

STEMI is acute myocardial infarction identified by new ST elevation at the J point in two contiguous leads in a compatible ischaemic presentation. The emergency label is made clinically and electrocardiographically so that reperfusion is not delayed. Final confirmation requires a rise and/or fall in cardiac troponin with at least one value above the 99th-percentile upper reference limit. Evidence of acute myocardial ischaemia must also be present.

First principles

The ECG pattern is a decision rule, not a histology report

Persistent regional ST elevation identifies the group that benefits from immediate reperfusion. It does not prove the artery is completely blocked or that necrosis is already full thickness. Troponin confirms infarction afterwards, and confirmation is a rise and/or fall with at least one value above the 99th-percentile upper reference limit plus evidence of acute ischaemia. That result arrives too late to be useful here, so it never delays reperfusion.

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