ST Elevation in Leads V4-6, II, and aVF: Inferior and Lateral Wall Involvement

Primary Wall Involvement

• The American College of Cardiology indicates that ST elevation in leads II, III, and aVF is associated with inferior wall myocardial infarction, while ST elevation in leads V4-6 indicates lateral wall involvement 2, 3

Most Likely Culprit Vessels

• A distal LAD occlusion with "wraparound" anatomy is the most common cause of this pattern, where the LAD extends beyond the apex to supply the inferior wall, as suggested by the American College of Cardiology and Circulation 2, 3, 1
• The American College of Cardiology recommends considering proximal RCA occlusion with right ventricular involvement as a less common cause of this pattern, with the spatial ST vector directed inferiorly, to the right, and anteriorly 2, 1

Critical Distinguishing Features

• The American College of Cardiology suggests that greater ST elevation in lead III than lead II indicates RCA occlusion rather than LAD 2, 1
• ST depression in leads I and aVL favors proximal RCA occlusion, according to the American College of Cardiology 2, 1

Immediate Clinical Actions

• The American College of Cardiology recommends recording right-sided chest leads V3R and V4R immediately in all patients presenting with this pattern 2, 1
• ST elevation ≥0.5 mm in V4R indicates right ventricular infarction, as indicated by the American College of Cardiology 2, 4

Reperfusion Therapy Indications

• The American College of Cardiology and the American Heart Association suggest that patients with ST elevation ≥1 mm in two contiguous limb leads (II, III, aVF) or ST elevation ≥2 mm in two contiguous precordial leads (V4-V6) meet criteria for immediate reperfusion therapy 5, 6
• Primary PCI is preferred over fibrinolysis when available, as it allows definitive identification of the culprit lesion, according to the American College of Cardiology 7

Common Pitfalls to Avoid

• The American College of Cardiology advises against delaying right-sided lead recording, as the diagnostic window for RV infarction is narrow 2, 1
• Avoid aggressive fluid resuscitation if RV infarction is present, as these patients are preload-dependent and may develop cardiogenic shock with standard inferior MI fluid management, as recommended by the American College of Cardiology 2
• The American College of Cardiology suggests avoiding the use of nitrates in RV infarction, as they can cause profound hypotension 2