What cardiac walls are involved if a patient presents with ST elevation in leads V2-4, III, and aVF on an electrocardiogram (ECG)?

Cardiac Wall Involvement with ST Elevation in V2-4, III, and aVF

This ECG pattern indicates involvement of both the anterior and inferior walls of the left ventricle, representing either a "wraparound" distal LAD occlusion or, less commonly, proximal RCA occlusion with right ventricular extension. 1, 2

Primary Interpretation

The combination of ST elevation in leads V2-4 (anterior leads) and leads III, aVF (inferior leads) creates a distinctive pattern that requires careful interpretation:

Walls Involved

• Anterior wall (indicated by V2-4 ST elevation) 1
• Inferior wall (indicated by III, aVF ST elevation) 1, 3
• Potentially apical and septal regions depending on the culprit vessel 1, 4

Most Likely Culprit Vessels

This combined pattern represents two distinct clinical scenarios:

Scenario 1: Distal LAD Occlusion (Most Common - 70% of cases)

• Mid-to-distal LAD occlusion with "wraparound" anatomy extending beyond the apex to supply the inferior wall 2
• The ST-segment vector is oriented more inferiorly when the occlusion is distal, causing ST elevation in both anterior and inferior leads 1
• These patients typically have smaller infarct size and better preserved LV function (median EF 0.53) compared to isolated anterior MI 2
• Critical warning: This pattern is associated with significantly increased risk of ventricular septal rupture (42.9% show this ECG pattern vs 3.6% without) 5

Scenario 2: Proximal RCA Occlusion (30% of cases)

• Proximal RCA occlusion with right ventricular involvement extending anteriorly 2, 6
• The spatial ST vector is directed inferiorly, to the right, AND anteriorly 7
• ST elevation in V1 ≥ V3 and absence of ST progression from V1 to V3 suggests RCA rather than LAD 2

Key Distinguishing Features

To Differentiate RCA from LAD as Culprit:

Favors Proximal RCA:

• ST elevation in V1 ≥ V3 2
• Lack of progressive ST elevation from V1 to V3 2
• Greater ST elevation in lead III than lead II 1, 3
• ST depression in leads I and aVL 1, 3
• Must obtain right-sided leads V3R and V4R immediately - ST elevation ≥1 mm in V4R confirms RV involvement 3

Favors Distal LAD:

• Progressive ST elevation pattern in precordial leads 1
• ST elevation may be present in lead II ≥ lead III 2
• Leads I and aVL may show isoelectric or elevated ST segments 1

Critical Clinical Actions

Immediate ECG Modifications Required:

• Record right-sided chest leads V3R and V4R immediately in all patients with this pattern 1, 3
• These must be obtained rapidly as ST elevation in right-sided leads resolves within 10 hours in 50% of patients 3

Prognostic Implications:

• Despite more extensive ST elevation across multiple leads (>6 leads in 83% of cases), these patients paradoxically have smaller infarct size (median peak CK 1370 IU vs 2381 IU for isolated anterior MI) 2
• However, mortality risk increases from 6% to 25-30% if RV infarction is present 3
• High risk for ventricular septal rupture - maintain heightened surveillance 5

Common Pitfalls to Avoid

• Do not assume isolated LAD occlusion based solely on anterior ST elevation - the inferior changes are real, not reciprocal 2
• Do not delay obtaining right-sided leads - the diagnostic window for RV involvement is narrow 3
• Do not underestimate infarct severity based on smaller enzyme elevation - these patients still require aggressive management 2
• Recognize that ST elevation in V1 with basal septal involvement increases risk of complications 4