How many electrocardiogram (ECG) leads must exhibit ST segment elevation for it to be considered significant?

From the Guidelines

ST segment elevation is considered significant when it appears in at least two contiguous leads on an electrocardiogram (ECG). The criteria for ST-elevation myocardial infarction (STEMI) require ST elevation of at least 1 mm (0.1 mV) in two or more anatomically contiguous leads, as stated in the 2017 ESC guidelines for the management of acute myocardial infarction in patients presenting with ST-segment elevation 1. For the precordial leads V2-V3, the threshold is slightly different: ≥2 mm (0.2 mV) for men ≥ 40 years, ≥2.5 mm (0.25 mV) for men < 40 years, and ≥1.5 mm (0.15 mV) for women.

Key Points to Consider

• The two-lead minimum is important because it helps distinguish true myocardial injury from normal variants or artifacts that might appear in a single lead.
• The requirement for contiguous leads reflects the anatomical distribution of coronary arteries, as myocardial infarction typically affects a specific region of the heart supplied by a particular coronary artery.
• When ST elevation appears in multiple adjacent leads, it suggests a genuine ischemic event rather than a technical error or normal variant, increasing the specificity of the diagnosis and helping clinicians make timely decisions about reperfusion therapy.

Clinical Application

In clinical practice, the diagnosis of STEMI is based on a combination of clinical symptoms, such as chest pain, and ECG findings, including ST-segment elevation in two or more contiguous leads 1. The 2010 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care also support this criteria 1. However, the most recent and highest quality study, the 2017 ESC guidelines, should be prioritized in clinical decision-making 1.

Threshold Values

The threshold values for ST-segment elevation consistent with STEMI are:

• J-point elevation 0.2 mV (2 mm) in leads V2 and V3 and 0.1 mV (1 mm) in all other leads for men ≥ 40 years old.
• J-point elevation 0.25 mV (2.5 mm) in leads V2 and V3 and 0.1 mV (1 mm) in all other leads for men < 40 years old.
• J-point elevation 0.15 mV (1.5 mm) in leads V2 and V3 and 0.1 mV (1 mm) in all other leads for women.

From the Research

ST Segment Elevation Criteria

• The definition of ST-segment elevation myocardial infarction (STEMI) requires pathologic ST-segment elevation occurring in at least 2 anatomically contiguous leads in a patient with a clinical presentation consistent with acute myocardial infarction (AMI) 2.
• Significant ST-segment elevation is defined as a shift > or = 1 mm during dobutamine compared to baseline in at least two contiguous infarct-related leads 3.
• ST-segment elevation in lead aVR is generally reciprocal to and accompanied by ST-segment depression in precordial leads, and predicts left main and/or three-vessel disease (LM/3VD) in patients with acute coronary syndromes 4.
• The STEMI criteria based on ST elevation in 10 pairs of contiguous leads have a high specificity but lower sensitivity, which can be improved by adding ST depression criteria, but at the cost of decreased specificity 5.
• The presence of reciprocal changes in prehospital ECG myocardial infarction criteria can improve the positive predictive value to more than 90% and include a significant majority of acute myocardial infarction patients with ST segment elevation who received thrombolytic therapy within five hours after hospital arrival 6.

Number of Leads Required

• At least 2 anatomically contiguous leads must exhibit ST segment elevation for it to be considered significant 2.
• Significant ST-segment elevation is defined as a shift > or = 1 mm during dobutamine compared to baseline in at least two contiguous infarct-related leads 3.
• The STEMI criteria are based on ST elevation in 10 pairs of contiguous leads 5.