What does an anterior infarct on an electrocardiogram (EKG) mean?

What Does an Anterior Infarct on EKG Mean?

An anterior infarct on EKG indicates myocardial infarction (heart attack) affecting the anterior wall of the left ventricle, typically caused by occlusion of the left anterior descending (LAD) coronary artery, and represents a medical emergency requiring immediate reperfusion therapy. 1

Anatomical Location and Coronary Artery Involvement

The anterior wall of the left ventricle is supplied by the LAD coronary artery, and occlusion at different points along this vessel determines the extent and specific pattern of infarction 2:

• Proximal LAD occlusion (before the first septal perforator and first diagonal branch) produces extensive anterior wall infarction with worse prognosis and higher mortality 2
• Mid-to-distal LAD occlusion typically causes anteroapical infarction without septal involvement 3
• First diagonal branch occlusion produces isolated mid-anterior or mid-anterolateral infarction without apical or septal involvement 4

EKG Findings in Anterior Infarction

Acute Phase (ST-Elevation Myocardial Infarction)

The hallmark of acute anterior infarction is ST-segment elevation in the anterior precordial leads 1:

• Primary anterior leads: V1, V2, V3, V4 show ST elevation 3
• The traditional term "anteroseptal MI" (ST elevation in V1-V3) is actually a misnomer - 92% of these patients have anteroapical infarction with a normal septum, not septal involvement 3

Specific EKG Patterns That Predict Proximal LAD Occlusion

These findings indicate proximal LAD occlusion and carry worse prognosis 2:

• ST elevation in lead aVR 2
• ST depression in lead V5 2
• ST elevation in V1 >2.5 mm 2
• ST depression ≥1 mm in inferior leads (II, III, aVF) 2

Post-Infarction Changes

After the acute phase, T-wave inversions develop in leads that previously showed ST elevation 5:

• T-wave inversions can persist from days to permanently 5
• Deeply inverted T waves (>0.5 mV) in leads V2-V4 with QT prolongation represent a critical warning pattern that indicates severe proximal LAD stenosis with collateral circulation 5
• If this pattern is not recognized and treated appropriately, a high percentage of patients will experience acute anterior wall infarction 5

Clinical Significance and Prognosis

Proximal LAD occlusion carries significantly higher mortality 2:

• In one study, 4 patients with proximal LAD occlusion died during hospitalization versus only 1 patient with distal occlusion (p ≤ 0.001) 2
• The location of LAD occlusion relative to major side branches has direct prognostic significance 2

Critical Action Points

When anterior infarction is identified on EKG 1:

• Immediate reperfusion of the occluded vessel must be the primary goal 1
• Even subtle signs of anterior wall infarction suggesting complete coronary occlusion should trigger urgent intervention 1
• The specific pattern of deeply inverted T waves with QT prolongation in leads V2-V4 should prompt urgent evaluation for severe proximal LAD stenosis, as these patients are at high risk for acute anterior wall infarction if not treated appropriately 5

Common Pitfalls to Avoid

• Do not dismiss "anteroseptal" changes as minor - these typically represent anteroapical infarction requiring the same urgent treatment as any anterior STEMI 3
• Do not overlook the warning pattern of deeply inverted T waves in V2-V4 - this indicates critical LAD stenosis even without active ST elevation 5
• Always assess for signs of proximal versus distal LAD occlusion using the specific EKG criteria above, as this has direct prognostic implications 2