ECG criteria
- Criteria are interpreted in the clinical context of suspected acute ischemia; the absence of typical chest pain does not rule out MI—with a convincing diagnostic ECG, the reperfusion strategy is not delayed while waiting for symptoms or troponin
- ST elevation is measured at the J point relative to the TP segment as the baseline; if the TP segment cannot be reliably identified, the PR segment is used
- In two contiguous leads of the same anatomical region (septal V1–V2, anterior V3–V4, lateral I, aVL, V5–V6, inferior II, III, aVF)
- In all leads except V2–V3: ST elevation ≥1 mm (0.1 mV)
- In V2–V3 in men ≥40 years: ST elevation ≥2 mm; in men <40 years: ≥2.5 mm
- In V2–V3 in women (regardless of age according to most sources): ST elevation ≥1.5 mm
- New or presumed new left bundle branch block is not an independent ECG criterion for STEMI on its own; in the presence of ongoing ischemia, hemodynamic instability, ventricular arrhythmias, or high probability of occlusion (Sgarbossa/modified Sgarbossa criteria), the patient is managed via an emergency protocol with urgent coronary angiography
- In suspected posterior MI, ST elevation ≥0.5 mm in at least two contiguous leads V7–V9 supports the diagnosis (in men <40 years — threshold ≥1 mm); horizontal ST depression in V1–V3 without elevation in standard leads also warrants evaluation of posterior leads and emergency management when clinical presentation is consistent
What it looks like on ECG
ST elevation is assessed at the J point—the junction between the QRS complex and the ST segment. The preferred baseline for measuring displacement is the TP segment; if the TP segment is indistinguishable (e.g., in tachycardia or due to baseline artifact), the PR segment is used. When pericarditis is suspected, the PR segment itself may be displaced, so the baseline in this case must be evaluated with particular caution. The 2009 AHA/ACCF/HRS and ESC criteria define thresholds by lead groups:
| Leads | ST elevation threshold |
|---|---|
| I, aVL, V5–V6, II, III, aVF, V1 | ≥1 mm (0.1 mV) |
| V2–V3, men ≥40 years old | ≥2 mm |
| V2–V3, men <40 years old | ≥2.5 mm |
| V2–V3, women | ≥1.5 mm |
| V7–V9 (posterior), ≥2 contiguous leads | ≥0.5 mm (men <40 years — ≥1 mm) |
Thresholds in V2–V3 are higher due to physiological J-point variability in young men (early repolarization, high QRS amplitude). The criterion requires elevation in two contiguous leads of the same wall—isolated elevation in a single lead is insufficient. The same applies to leads V7–V9: they are supplementary and used specifically when posterior MI is suspected (e.g., in the presence of ST depression in V1–V3), rather than as an independent universal STEMI criterion based on a single lead. The morphology of ST elevation (concave, convex, "tombstone") is not formally defined by the criteria, but convex elevation and the "tombstone" pattern increase the likelihood of true occlusion. Reciprocal changes (ST depression in opposite leads) are assessed in parallel—they increase diagnostic confidence.
Mechanism
Acute myocardial injury and ischemia during coronary occlusion alter currents of injury between the affected and healthy myocardium. This creates a directed electrical vector that causes ST elevation in leads facing the lesion zone and reciprocal depression in opposite leads. The ECG alone cannot reliably assess the depth and transmurality of the injury and does not replace clinical assessment of the probability of acute occlusion. The earlier from the onset of occlusion the ECG is recorded and the larger the zone of acute ischemia, the more pronounced the ST elevation, often preceded by hyperacute T waves.
Causes
- Acute thrombotic occlusion of a coronary artery (primary cause)
- Coronary spasm (Prinzmetal angina) — transient ST elevation
- Coronary artery dissection
- Coronary artery embolism
- Pronounced diffuse subendocardial ischemia in left main coronary artery disease, proximal LAD, or multiview/multivessel disease — may be accompanied by ST elevation in aVR alongside widespread ST depression
Differential diagnosis
- Early repolarization syndrome — concave ST elevation, J-point notch, stable pattern without dynamics, no clinical ischemia
- Pericarditis — diffuse, usually concave ST elevation and PR depression, without reciprocal depression outside of aVR and sometimes V1
- Left bundle branch block (chronic) — requires modified Sgarbossa (Smith) criteria to assess for ischemia
- Left ventricular aneurysm — persistent ST elevation in the area of an old infarction with pathological Q waves, without dynamics or clinical symptoms
- Brugada pattern type 1 — ST elevation only in V1–V2 with a descending ("coved") segment, different context
- Hyperkalemia — ST elevation may be combined with wide QRS and absent P waves, but the morphology and clinical picture are different
- De Winter waves and ST elevation in aVR — high-risk occlusion patterns without formal STEMI criteria, requiring separate interpretation and urgent evaluation
Clinical significance and management
Meeting STEMI criteria in suspected acute ischemia is an indication for an immediate reperfusion strategy; a single diagnostic ECG is sufficient for its activation. Primary PCI is preferred if it can be performed in a timely manner; if an expected delay to PCI of more than 120 minutes is anticipated in a suitable patient with symptom onset typically under 12 hours, fibrinolysis should be considered followed by a pharmacoinvasive strategy and mandatory rescue PCI if it fails. If the initial ECG is non-diagnostic, repeat recordings are performed at short intervals and when symptoms change, comparing with previous tracings, but without delaying treatment when the picture is already convincing.
When the presentation does not meet classical thresholds but acute occlusion is suspected, the approach varies by pattern. Posterior MI (ST depression in V1–V3 confirmed by V7–V9) and the de Winter pattern require immediate consultation with the interventional team and are generally managed as acute occlusion without waiting for formal criteria in V1–V6. ST elevation in aVR alongside widespread ST depression is a marker of high risk for severe ischemia, suggesting left main or multivessel disease; it requires urgent clinical and invasive evaluation, but is not considered an automatic STEMI equivalent. The Aslanger pattern is described as a high-risk sign requiring urgent evaluation rather than an independent diagnostic STEMI criterion. For MI in the setting of LBBB or a pacemaker, modified Sgarbossa criteria are applied, while also assessing for refractory ischemia and hemodynamic instability.
Common interpretation errors
- Measuring ST elevation not at the J point, but in the middle of the ST segment or at the T-wave peak
- Using a uniform threshold of 1 mm for V2–V3 without regard to sex and age
- Assessing ST elevation in a single lead without confirmation by a contiguous lead of the same wall (including V7–V9)
- Automatically equating a new LBBB or ST elevation in aVR with a STEMI diagnosis without evaluating the clinical context, Sgarbossa criteria, and dynamics
- Waiting for a repeat ECG or troponin dynamics before activating a reperfusion strategy when the diagnostic picture is already convincing
1. What is the J-point ST-elevation threshold accepted for leads V2–V3 in men aged 40 years and older?
For men ≥40 years in V2–V3, the threshold is ≥2 mm, whereas in men under 40, the threshold is higher at ≥2.5 mm.
2. How many contiguous leads of the same anatomical wall must meet the ST-elevation criterion to diagnose STEMI?
The criterion requires ST elevation above the threshold in at least two contiguous leads of the same region, rather than in a single lead.
3. Which finding is considered a high-risk pattern for acute occlusion of the left anterior descending artery without formal compliance with standard STEMI criteria in V1–V6?
De Winter waves are a characteristic pattern of acute occlusion of the left anterior descending artery, which are managed as acute ischemia even though formal ST-elevation criteria may be absent.
Frequently asked questions
What is the ST-segment elevation threshold in V2–V3 for women?
≥1.5 mm (≥0.15 mV) regardless of age, which is lower than the threshold for men—the difference is due to the smaller physiological amplitude of early repolarization in women.
Can a STEMI diagnosis be made with ST elevation in only a single lead?
No, the formal criterion requires elevation in two contiguous leads of the same anatomical wall. Isolated elevation in a single lead requires additional evaluation of dynamics and clinical context.
What to do if ST elevation does not reach the threshold, but there is a strong clinical presentation of ischemia and de Winter waves?
This presentation is interpreted as a high-risk occlusion pattern and managed as acute ischemia without waiting for formal compliance with STEMI criteria—delay increases the infarct size. The decision is made by the interventional team taking the clinical context into account.
What is the difference between STEMI criteria and Sgarbossa criteria?
STEMI criteria are applied in the presence of a normal or minimally altered QRS complex, whereas Sgarbossa criteria (and their Smith modification) are specifically designed to assess ischemia in the setting of LBBB or ventricular pacing, where standard ST-segment elevation is uninformative.
Is a repeat ECG necessary in suspected STEMI without overt criteria?
Yes, if the initial ECG is non-diagnostic: a repeat tracing is performed after a short interval and upon symptom changes, comparing it with previous strips. When the diagnostic picture is already convincing, a repeat tracing is unnecessary and must not delay reperfusion.
ECG Course
Interpretation from basics to myocardial infarction — learn to read any ECG using a systematic algorithm.
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Related terms
More in the section "Criteria, Formulas, Algorithms"
Sources
- AHA/ACCF/HRS Recommendations for the Standardization and Interpretation of the ECG, 2009
- ESC Guidelines for the management of acute coronary syndromes, 2023
- Surawicz B., Knilans T. Chou's Electrocardiography in Clinical Practice
- Orlov V.N. Guide to Electrocardiography
Educational material for medical students and physicians. Does not replace clinical guidelines and physical examination; the ECG must always be interpreted in conjunction with the clinical picture.