23-02: Acute Anterior Myocardial Infarction

ECG Findings

• ST-segment elevation in the precordial leads (V₁-V₆).

• Q-wave formation in the precordial leads (V₁-V₆).

• Reciprocal ST-segment depression in the inferior leads (II, III, aVF).

• V₁-V₂: Septal injury.

• V₃-V₄: Anterior injury.

• V₅-V₆, I, and aVL: Anterolateral injury. Lateral injury may involve leads I and aVL only, and this is sometimes referred to as “high lateral” injury.

Pearls

1. Anterior STEMI results from occlusion of the left anterior descending (LAD) artery.

2. Anterior STEMI due to LAD artery occlusion has the worst prognosis of all STEMI locations. This is due to the large territory supplied by the LAD.

3. The reciprocal changes seen in the inferior leads (II, III, and aVF) are proportional to the magnitude of the ST elevations in I and aVL, and hence may be absent if the anterior STEMI does not involve the high lateral leads.

4. A “wrap around LAD” occlusion can produce ST elevations in not only the anterior precordial leads but also the inferior and lateral leads. This type of STEMI can easily be mistaken for pericarditis or early repolarization because of the ST elevations in multiple vascular territories and the absence of reciprocal ST depression.