Acute Anterior Myocardial Infarction
- ST segment elevation in the anterior precordial leads.
- Commonly-used terminology for injury location:
- V3-V4: Anterior injury.
- V1-V4: Anteroseptal injury.
- V3-V6: Anterolateral injury. Leads I and aVL may also be involved, especially if the circumflex artery is affected (high lateral injury).
- Reciprocal ST segment depressions are often present in the inferior leads (II, III, aVF).
Acute Anteroseptal Myocardial Infarction. (ECG contributor: James V. Ritchie, MD.)
Pathologic ST-segment elevation beyond 1 mm (double arrow) with pathologic Q waves (arrow) in lead V3. The ST segment demonstrates a convex upward, or "tombstone" morphology.
The left anterior descending artery supplies blood to the anterior and lateral left ventricle and ventricular septum.
Normal R-wave progression (increasing upward amplitude with R wave > S wave at V3 or V4) may be interrupted.
The development of pathologic Q waves in any of the V leads other than V1 strongly suggests that the injury has progressed to an infarction, as seen in this example.
Acute Inferior Myocardial Infarction
- ST segment elevation in inferior leads (II, III, aVF)
- Reciprocal ST segment depressions in the anterior leads (V1-V3) and possibly high lateral leads (I, aVL)
Acute Inferior-Posterior Myocardial Infarction. (ECG contributor: James V. Ritchie, MD.)
ST-segment elevation is present in the inferior leads (II, III, aVF) (arrow), with reciprocal ST depression in the anterior leads (V2-V4) (arrowhead) and high lateral leads (I, aVL).
The right coronary artery supplies blood to the right ventricle, the SA node, the inferior portions of the left ventricle, and usually to the posterior portion of the left ventricle and the AV node.
Infarctions involving the SA node may produce sinus dysrhythmias including tachycardias, bradycardias, and sinus arrest.
Infarctions involving the AV node may produce AV blocks.
In the presence of acute inferior injury, especially if the ST segment elevation in III is higher than in II, a right-sided ECG should be obtained to look for right ventricular involvement. The administration of nitroglycerin in the presence of acute right ventricular infarction can precipitate profound hypotension, as these patients are preload dependent.
Since the right coronary artery so often supplies the posterior left ventricle, look carefully for evidence of a posterior infarction (as present ...
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