What coronary artery is most likely involved in an infarction with ECG changes in leads V1-V4?

ECG Changes in Leads V1-V4 Indicate Left Anterior Descending Artery Occlusion

ECG changes in leads V1-V4 strongly indicate an infarction in the left anterior descending (LAD) coronary artery. 1 This pattern represents anterior wall ischemia/infarction, which is invariably due to occlusion of the LAD artery.

Anatomical Correlation Between ECG Leads and Coronary Arteries

The 12-lead ECG provides valuable information about the location of myocardial infarction by showing characteristic changes in specific leads that correspond to different anatomical regions of the heart:

• V1-V4 (Anterior leads): Monitor the anterior wall of the left ventricle

  • Supplied by: Left Anterior Descending (LAD) artery
  • ECG changes: ST-segment elevation in these leads indicates anterior wall ischemia/infarction 1

• II, III, aVF (Inferior leads): Monitor the inferior wall of the left ventricle

  • Supplied by: Right Coronary Artery (RCA) or Circumflex (LCx) artery
  • Often show reciprocal ST depression when anterior leads show elevation

• V5-V6, I, aVL (Lateral leads): Monitor the lateral wall of the left ventricle

  • Supplied by: Circumflex (LCx) artery or diagonal branches of LAD

Further Localization of LAD Occlusion

The specific pattern of ST changes can help determine the location of occlusion within the LAD:

1. Proximal LAD occlusion (above first septal and first diagonal branches):

   • ST elevation in V1-V4, I, aVL, and often aVR
   • Reciprocal ST depression in inferior leads (II, III, aVF)
   • Often ST depression in V5
   • ST elevation in V1 > 2.5 mm 2, 3
   • Associated with worse prognosis due to larger area of myocardium at risk 4

2. Mid-LAD occlusion (between first septal and first diagonal):

   • ST elevation in V2-V4, but not in V1
   • ST elevation in aVL
   • ST depression in lead III 1

3. Distal LAD occlusion (below first septal and first diagonal):

   • ST elevation predominantly in V3-V6
   • Less prominent ST elevation in V2
   • No ST elevation in V1, aVR, or aVL
   • Absence of ST depression in inferior leads 1, 3
   • Abnormal Q waves in V4-V6 3

Clinical Significance

The ability to identify the LAD as the culprit artery and localize the occlusion site has important clinical implications:

• Prognosis: Proximal LAD occlusions are associated with higher morbidity and mortality due to the larger territory at risk 4
• Treatment decisions: May influence decisions regarding reperfusion therapy and triage to PCI-capable centers
• Risk stratification: Patients with proximal LAD occlusions may require more aggressive monitoring and management

Diagnostic Accuracy

Research has shown that specific ECG patterns can predict LAD occlusion with high specificity:

• ST elevation in aVR has 97% specificity for proximal LAD occlusion 5
• ST depression in inferior leads (II, III, aVF) has sensitivity of 84-88% for proximal LAD occlusion 5
• The presence of R waves in V2 suggests higher ejection fraction and more distal LAD occlusion 6

Common Pitfalls

1. Left Bundle Branch Block: ST-segment criteria for diagnosis of acute ischemia are affected by LBBB due to secondary ST and T-wave changes 1

2. Right Bundle Branch Block: ST-segment criteria are generally not affected by RBBB 1

3. Post-ischemic T-wave changes: Deeply inverted T waves in V2-V4 with QT prolongation may indicate severe stenosis of the proximal LAD with collateral circulation rather than acute occlusion 1

4. Posterior wall involvement: Can cause ST depression in V1-V3, which might be misinterpreted as reciprocal changes from an inferior MI rather than direct evidence of posterior wall ischemia 1

In conclusion, ECG changes in leads V1-V4 are highly specific for LAD artery occlusion, with the pattern of changes helping to localize the site of occlusion within the vessel.