What does ST elevation in leads II, III, and aVF indicate?

ST Elevation in Leads II, III, and aVF: Diagnosis and Implications

ST elevation in leads II, III, and aVF indicates an inferior wall myocardial infarction, most commonly due to right coronary artery (RCA) occlusion, especially when ST elevation is greater in lead III than in lead II and is associated with ST depression in leads I and aVL. 1

Anatomical Significance

• The inferior wall of the left ventricle is represented by leads II, III, and aVF
• When ST elevation appears in these leads, it indicates acute injury to the inferior myocardial wall
• This pattern has specific implications for identifying the culprit vessel:
  • Right coronary artery (RCA) occlusion: When ST elevation is greater in lead III than lead II, often with ST depression in leads I and aVL 1
  • Left circumflex artery (LCx) occlusion: When ST elevation is more balanced between leads II and III 1

Associated Findings to Look For

Right Ventricular Involvement

• When the RCA is occluded proximally, right ventricular infarction may occur
• This presents as:
  • ST elevation in right-sided chest leads (VR and V4R)
  • Often ST elevation in lead V1 1
• Important: ST elevation in right-sided leads disappears more quickly than inferior lead changes, so record these leads as soon as possible 1

Reciprocal Changes

• ST depression in leads I and aVL (high lateral leads) is common with inferior STEMI
• ST depression in anterior leads (V1-V4) may represent reciprocal changes or posterior wall involvement 2
• These reciprocal changes can help confirm a true STEMI versus false positives 2

Clinical Implications

• Inferior wall infarctions generally have better prognosis than anterior infarctions
• However, complications to watch for include:
  • Right ventricular involvement (in proximal RCA occlusions)
  • Bradyarrhythmias and heart blocks (due to AV node ischemia)
  • Hypotension (especially with RV involvement)

Management Considerations

• Immediate reperfusion therapy is indicated for STEMI patients presenting within 12 hours of symptom onset 1
• ECG criteria for fibrinolytic therapy include ≥1 mm ST elevation in 2 or more contiguous limb leads (II, III, aVF) 1
• Right-sided ECG leads (V3R and V4R) should be recorded in all patients with inferior wall STEMI to assess for right ventricular involvement 1
• Standard STEMI care includes:
  • Antiplatelet therapy (aspirin plus P2Y12 inhibitor)
  • Anticoagulation
  • Cardiac monitoring for arrhythmias
  • Reperfusion therapy (preferably PCI within 120 minutes) 2

Important Pitfalls to Avoid

• Don't miss right ventricular involvement, which requires careful fluid management and avoidance of preload-reducing medications
• Don't confuse reciprocal changes in anterior leads with a separate anterior wall infarction
• Remember that ST elevation in inferior leads with ST elevation in V5-V6 may indicate a larger infarct territory and poorer myocardial reperfusion 3
• Comparing the degree of ST elevation between lead III and V6 can help predict the culprit artery (III > V6 suggests RCA; III ≤ V6 suggests LCx) 3

In summary, ST elevation in leads II, III, and aVF represents an inferior wall myocardial infarction that requires prompt recognition, assessment for right ventricular involvement, and appropriate reperfusion therapy to minimize morbidity and mortality.