What degree of ST segment elevation is considered normal on an electrocardiogram (ECG)?

From the Guidelines

Normal ST segment elevation on an electrocardiogram (ECG) is typically less than 1 mm (0.1 mV) in limb leads and less than 2 mm (0.2 mV) in precordial leads, with specific thresholds for leads V2-V3 being less than 2 mm in men ≥40 years, less than 2.5 mm in men <40 years, and less than 1.5 mm in women regardless of age, as recommended by the 2025 ACC/AHA/ACEP/NAEMSP/SCAI guideline for the management of patients with acute coronary syndromes 1. These measurements are taken at the J point, where the QRS complex meets the ST segment. Some physiologic ST elevation can occur as a normal variant, particularly in young males, athletes, and in leads V2-V3, which is known as early repolarization pattern. In these cases, the ST elevation is usually concave upward (rather than convex or straight), which helps distinguish it from pathological elevation. The normal ST segment represents the early phase of ventricular repolarization, and slight elevation can reflect normal variations in this process. When evaluating ST segments, it's essential to consider the patient's baseline ECG, clinical context, and other ECG findings, as ST elevation beyond these normal limits may indicate serious conditions like myocardial infarction, pericarditis, or other cardiac pathologies. Key points to consider when evaluating ST segment elevation include:

• The degree of elevation, with higher elevations being more concerning for pathology
• The leads involved, with elevations in leads V2-V3 being more common as a normal variant
• The shape of the ST segment, with concave upward elevations being more likely to be benign
• The clinical context, with patients presenting with signs and symptoms of myocardial ischemia requiring a high index of suspicion for acute coronary syndromes 1. It's also important to note that the absence of electrocardiographic evidence of ischemia does not exclude acute coronary syndromes, and a high index of suspicion is warranted for those who present with signs and symptoms that could be consistent with myocardial ischemia 1. In contrast to earlier guidelines, such as the 2009 AHA/ACCF/HRS recommendations for the standardization and interpretation of the electrocardiogram 1, the 2025 ACC/AHA/ACEP/NAEMSP/SCAI guideline provides more specific and updated thresholds for ST segment elevation, making it a more reliable reference for clinical practice.

From the Research

ST Segment Elevation on an Electrocardiogram (ECG)

The degree of ST segment elevation considered normal on an electrocardiogram (ECG) is not explicitly defined in the provided studies. However, the studies discuss various aspects of ST segment elevation in different clinical contexts:

• The studies focus on ST segment elevation in the context of acute coronary syndromes, myocardial infarction, and coronary artery vasospasm 2, 3, 4, 5, 6.
• ST segment elevation is a critical diagnostic criterion for ST-elevation myocardial infarction (STEMI) 3, 5.
• The morphology and magnitude of ST segment elevation can vary, with some studies noting that concave ST elevation is more common in patients without culprit lesions on coronary angiography 3.
• Transient ST segment elevation is a significant predictor of adverse hospital outcomes and death in patients with acute coronary syndromes 4.

Key Findings

• There is no specific mention of a normal degree of ST segment elevation in the provided studies.
• The studies emphasize the importance of considering the clinical context, ECG morphology, and patient symptoms when interpreting ST segment elevation.
• ST segment elevation is a critical diagnostic criterion for various cardiac conditions, and its interpretation requires careful consideration of multiple factors 2, 3, 4, 5, 6.

Clinical Implications

• The provided studies highlight the complexity of interpreting ST segment elevation on an ECG.
• Clinicians must consider multiple factors, including patient symptoms, ECG morphology, and clinical context, when interpreting ST segment elevation.
• Further research is needed to establish clear guidelines for the interpretation of ST segment elevation in different clinical contexts.