Pearls of Knowledge: Acute Anteroseptal Wall MI
Wednesday, March 12, 2025
12-Lead ECG Interpretation: Acute Anteroseptal Wall MI
Pearls of Knowledge © BrainyNurses.com
A lot of information can be gleaned from a 12-Lead ECG and using systematic steps will help to identify all the components. Considering the patient’s history and clinical presentation can provide some helpful clues as to what to look for, especially if you are more of a novice in 12-Lead interpretation. The focus for this 12-Lead interpretation is to look for evidence of ischemia, injury, or infarction.
History and Clinical Correlation
58-year-old female with a history of intermittent chest pain for the past few hours which would lessen at rest. She is anxious, cool, and clammy. An S3 and persistent bilateral crackles are heard on auscultation. BP 105/60.
Systematic Steps in Interpretation
Steps when chest pain is present.
• Identify the rhythm.
• Determine axis (Memory Hint: “Right together, Left apart” using leads I and aVF).
• Look for signs of an acute MI (ST segment elevation of 1 mm or more).
• Look for signs of ischemia (ST segment depression and symmetrically inverted T waves).
• Look for signs of myocardial necrosis (Q wave more than 1/3 the height of the R wave).
Using this guide, evaluate axis, the leads identified for the above changes, and the impression.
Interpretation
Sinus rhythm with normal intervals.
Lead I is positive and Lead aVF is a little more positive (point up). Normal axis.
Axis is important to look at with an acute MI. A conduction defect, such as fascicular blocks will cause an axis shift, and failure to recognize the block could be lethal.
ST segment elevation is present in V3 and is almost isoelectric in V4 (anterior) with inverted T waves in both leads. Anterior wall MI.
Anterior wall occurs in conjunction with septal wall MI. ST segment elevation in V1 and V2 with inverted T waves. Anteroseptal MI.
If ST segment elevation were present in Leads I, aVL, and V5-V6, it would be referred to as an anteroseptal with lateral extension.
The inverted T waves in Leads V1-V4 are indicative of an “evolving” acute MI.
Pathological Q waves are present in V1-V2 signifying myocardial necrosis.
Clinical Significance
Anterior wall MI rarely occurs alone. When lateral or septal involvement is present with the anterior wall, complications may include severe left ventricular dysfunction resulting in heart failure, cardiogenic shock, and a high mortality. The clinical presentation indicates early shock as evidenced by normotension, cool, clammy, and restlessness. The S3 and persistent bilateral crackles are indicative of heart failure.
An anterior wall MI is caused by an occlusion of the left anterior descending artery.
Summary
A systematic approach to 12-Lead ECG interpretation is essential in detecting changes and applying them to the clinical setting. Changes occur with numerous conditions including acute coronary syndrome, other pathological disorders, conduction disturbances, electrolyte and acid base imbalances, and with medications.
To enhance care provided for cardiac patients, check out Clinical Application and Interpretation of the 12-Lead ECG. It is on-line, on-demand, with voice-over-power-point, and a comprehensive review to use at the bedside.
The extensive handout is easy to follow and includes a composite reference sheet to use in the session and post on the clinical unit afterwards. In addition, “In My Pocket” cards are included as a ready reference tool.
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