An anterior wall myocardial infarction (AWMI or anterior STEMI) occurs when anterior myocardial tissue usually supplied by the left anterior descending coronary artery (LAD) suffers injury due to lack of blood supply. When an AWMI extends to the septal and lateral regions as well, the culprit lesion is usually more proximal in the LAD or even in the left main coronary artery. This large anterior myocardial infarction is termed an "extensive anterior".
The ECG findings of an acute anterior wall myocardial infarction include:
1. ST segment elevation in the anterior leads (V3 and V4) at the J point and sometimes in septal or lateral leads depending on the extent of the myocardial infarction. This ST elevation is concave downward and frequently overwhelms the T wave. This is called "tombstoning" due to the similarity to the shape of a tombstone.
2. Reciprocal ST segment depression in the inferior leads (II, III and aVF).
According to the ACC/AHA guidelines for STEMI, there must be “New ST elevation at the J point in at least 2 contiguous leads of ≥ 2 mm (0.2 mV) in men or 1.5 mm (0.15 mV) in women in leads V2–V3 and/or of ≥1 mm (0.1 mV) in other contiguous chest leads or the limb leads.” Thus, 1 mm in any 2 contiguous leads EXCEPT leads V2 or V3 where the elevation must be 2 mm in men or 1.5 mm in women. See the full 12-lead ECG example below and a few more at the bottom:
The ECG findings of an OLD anterior wall myocardial infarction include the loss of “anterior forces” leaving Q waves in leads V1 and V2. This is a cause of "poor R wave progression" or PRWP. Below is an example of an old anterior myocardial infarction:
Note: To distinctly say that an old anterior wall myocardial infarction is present on the ECG, there must be no identifiable R wave in lead V1 and usually V2 as well. If there is an R wave in V1 or V2, the term poor R wave progression can be used, but not an old anterior wall myocardial infarction.
On rare occasions, persistent ST elevation may be seen in V1 and/or V2 indicating a ventricular aneurysm which is a known complication of a myocardial infarction (see ventricular aneurysm ECG review or ventricular aneurysm review section). An example of an old anterior myocardial infarction with a left ventricular aneurysm is below:
Infarcts and Ischemia ECG Quiz
Topic Review: STEMI
1. Surawicz B et al. ACC/AHA recommendations for the standardization and interpretation of the electrocardiogram. Circulation. 2009;119:e235-240.
2. Chou's Electrocardiography in Clinical Practice: Adult and Pediatric, 6e
By Steven Lome