Clinical Notes : Cardiology

146. ECG STEMI - anterior

ECG - Anterior STEMI

Anterior ST Elevation Myocardial Infarction

MI is myocardial cell death that occurs because of a prolonged mismatch between perfusion and demand.

This is usually caused by occlusion in the coronary arteries. ST-elevation myocardial infarction (STEMI) is suspected when a patient presents with persistent ST-segment elevation in 2 or more anatomically contiguous ECG leads in the context of a consistent clinical history.

 

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

Anterior myocardial infarction carries the worst prognosis of all infarct locations, mostly due to larger infarct size.

 

Patterns of Anterior Infarction

 

The nomenclature of anterior infarction can be confusing, with multiple different terms used for the various infarction patterns.

 

The following is a simplified approach to naming the different types of anterior MI.

The precordial leads can be classified as follows:

  • Septal leads = V1-2

  • Anterior leads = V3-4

  • Lateral leads = V5-6

 

The different infarct patterns are named according to the leads with maximal ST elevation:

  • Septal = V1-2

  • Anterior = V2-5

  • Anteroseptal = V1-4

  • Anterolateral = V3-6, I + aVL

  • Extensive anterior / anterolateral = V1-6, I + aVL

 

(NB. While these definitions are intuitive, there is often a poor correlation between ECG features and precise infarct location as determined by imaging or autopsy.)

 
 

Example 1 : Hyperacute Anteroseptal STEMI

  • ST elevation is maximal in the anteroseptal leads (V1-4).

  • Q waves are present in the septal leads (V1-2).

  • There is also some subtle STE in I, aVL and V5, with reciprocal ST depression in lead III.

  • There are hyperacute (peaked ) T waves in V2-4.

  • These features indicate a hyperacute anteroseptal STEMI

Hyperacute Anteroseptal STEMI

 

Example 2a : Hyperacute Anterior STEMI

  • There are hyperacute T-waves in V2-6 (most marked in V2 and V3) with loss of R wave height.

  • The rhythm is sinus with 1st degree AV block.

  • There are premature atrial complexes (beat 4 on the rhythm strip) and multifocal ventricular ectopy (PVCs of two different types), indicating an “irritable” myocardium at risk of ventricular fibrillation.

Hyperacute Anterior STEMI (a)

Example 2b : Hyperacute Anterior STEMI

A ECG of the same patient taken around 40-50 minutes later:

  • There is progressive ST elevation and Q wave formation in V2-5

  • ST elevation is now also present in I and aVL.

  • There is some reciprocal ST depression in lead III.

 

This is an acute anterior STEMI – this patient needs urgent reperfusion !

 

Hyperacute Anterior STEMI (b)

Example 3 : Extensive Anterolateral STEMI (acute)

  • ST elevation in V2-6, I and aVL.

  • Reciprocal ST depression in III and AVF.

 

Extensive Anterolateral STEMI (acute)

Example 4 : Extensive Anterior STEMI (acute)

  • ST elevation in V1-6 plus I and aVL (most marked in V2-4).

  • Minimal reciprocal ST depression in III and aVF.

  • Q waves in V1-2, reduced R wave height (a Q-wave equivalent) in V3-4.

  • There is a premature ventricular complex (PVC) with “R on T’ phenomenon at the end of the ECG; this puts the patient at risk for malignant ventricular arrhythmias

 

Extensive Anterior STEMI (acute)

Example 5 : Prior Anteroseptal / Lateral MI

  • Deep Q waves in V1-3 with markedly reduced R wave height in V4.

  • Residual ST elevation in V1-3 (“left ventricular aneurysm” morphology).

  • Biphasic/inverted T waves in V1-5.

  • Poor R wave progression (R wave height < 3mm in V3).

  • Abnormal Q waves and T-wave inversion in I and aVL.

  • The pattern indicates prior infarction of the anteroseptal and lateral walls.

 

Prior Anteroseptal / Lateral MI

 

Example 6 : Extensive anterior MI (“tombstoning” pattern)

  • Massive ST elevation with “tombstone” morphology is present throughout the precordial (V1-6) and high lateral leads (I, aVL).

  • This pattern is seen in proximal LAD occlusion and indicates a large territory infarction with a poor LV ejection fraction and high likelihood of cardiogenic shock and death.

Extensive anterior MI (“tombstoning” pattern)

 

Example 7 : Anterior-inferior STEMI

  • ST elevation is present throughout the precordial and inferior leads.

  • There are hyperacute T waves, most prominent in V1-3.

  • Q waves are forming in V1-3, as well as leads III and aVF.

  • This pattern is suggestive of occlusion occurring in “type III” or “wraparound” LAD (i.e. one that wraps around the cardiac apex to supply the inferior wall)

Anterior-inferior STEMI

 

Management

Refer A+E

In OOH settings where delay in transfer to A+E is inevitable : 

  • aspirin

    • 300 mg orally immediately, followed by 75 mg once daily

  • oxygen

    • Supplemental oxygen is indicated only if oxygen saturation is less than 90%

  • morphine

    • 2-4 mg intravenously every 5-15 minutes until adequate pain control is achieved

  • glyceryl trinitrate

    • if not hypotensive :

      • 0.3 to 1 mg sublingually every 5 minutes,

      • maximum 3 doses

    • if hypertensive or heart failure

      • 5 micrograms/minute intravenously initially,

      • increase by 5-20 microgram/minute increments every 3-5 minutes according to response,

      • maximum 200 micrograms/minute

 
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Life in the Fast Lane

Austalian Emergency Medicine website. 

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ST-elevation myocardial infarction

BMJ Best Practice

Last reviewed : March 2019

Last updated : September 2018

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