Identification and Localization of STEMI: The ANTERIOR-LATERAL WALL

Sometimes, STEMI's don't adhere to precise geographical boundaries! Depending upon the precise location of the ruptured plaque, changes associated with STEMI can encompass more than one "territorial area." Consider the following ECG.

I. Identify the rhythm

The rhythm is sinus. There is a P wave associated with every QRS. The rate is regular.

II. Identify the ischemic changes

ST segment elevation is present in the following leads:

• Lead I
• Lead aVL 
• Lead V2
• Lead V3
• Lead V4
• Lead V5
• Minimal STE in Lead V6

Reciprocal change in the form of ST segment depression is seen in the inferior leads:

• Lead II
• Lead III
• Lead aVF

Finally, notice that the R wave amplitude is largely negative throughout leads V1-V4. In "normal" ECGs, the transition to a positively deflected complex should begin around V3. This ECG showcases the concept of "poor R wave progression" which may be common post myocardial infarction. The septal Q waves are thought to represent necrotic myocardial tissue that no longer conducts electricity. Therefore, the electrical vectors are traveling AWAY from leads V1-V4. 

III. Interpretation

Sinus rhythm, rate of 70, ST segment elevation in leads I, aVL. STE also present in leads V2-V5. ECG consistent with an anterior-lateral ST segment elevation myocardial infarction. Occlusion of the left main, left anterior descending, and/or left circumflex coronary artery can contribute to this type of electrocardiographic presentation.