Which electrocardiogram (ECG) leads are affected in an anterior myocardial infarction (MI)?

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From the Guidelines

In an anterior myocardial infarction (MI), the ECG leads that are primarily affected are V1 through V4, which are the precordial leads that face the anterior wall of the left ventricle, as well as leads I and aVL, which may also show changes due to their view of the anterolateral heart surface. These leads typically show ST-segment elevation, pathological Q waves, and T-wave inversions during an anterior MI. The anterior wall of the left ventricle is typically supplied by the left anterior descending (LAD) coronary artery, so an occlusion in this vessel is usually responsible for anterior MIs.

Key Points

  • The ECG changes in anterior MI occur because the damaged myocardium cannot conduct electrical impulses normally, resulting in altered depolarization and repolarization patterns 1.
  • Anterior MIs are particularly concerning because they often involve a large area of myocardium and can lead to significant complications such as heart failure, arrhythmias, and cardiogenic shock.
  • Prompt recognition of these ECG changes is crucial for early intervention with reperfusion therapy to salvage myocardium and improve outcomes.

ECG Interpretation

  • ST-segment elevation in leads V1 through V4, as well as in leads I and aVL, is suggestive of an extensive anterior wall or anterobasal ischemia/infarction due to occlusion of the proximal portion of the left anterior descending coronary artery 1.
  • The location of the occlusion within the left anterior descending coronary artery can be suggested by the chest leads in which the ST-segment elevation occurs and the presence of ST-segment elevation or depression in other leads 1.

Clinical Implications

  • Early recognition and treatment of anterior MI are critical to improve outcomes and reduce morbidity and mortality.
  • The use of reperfusion therapy, such as percutaneous coronary intervention (PCI) or thrombolysis, can help to restore blood flow to the affected area of the heart and reduce the size of the infarct 1.
  • Close monitoring and follow-up are necessary to detect any potential complications and to optimize treatment.

References

1
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

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This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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