LAD Occlusion Often Presents Without Reciprocal Changes

Acute anterior STEMI tends to be a more difficult ECG diagnosis than acute inferior STEMI.

That’s because with acute inferior STEMI there’s almost always a downsloping ST-segment in lead aVL to help shore up the diagnosis.

Unfortunately, LAD occlusion does not always present with reciprocal changes, so we need to have other strategies to help rule-in the diagnosis.

Let’s look at some examples.

Example 1

obvious LAD occlusion with reciprocal changes

ST-segment elevation is present in leads V1-V4. There is reciprocal ST-segment depression in leads II, III, aVF, and V6.

In this case there is obvious ST-segment elevation in the anterior leads with reciprocal changes in the inferior leads. Assuming the patient has signs and symptoms of ACS, this should be an easy diagnosis.

Let’s look at another.

Example 2

LAD occlusion with reciprocal changes

There are hyperacute T-waves in leads V2-V6. There is ST-segment elevation in leads I and aVL with reciprocal ST-segment depression in leads II, III, and aVF.

In this case you can make the diagnosis based on the precordial leads alone, even though there is no ST-segment elevation. Why? Because the T-waves are hyperacute! You might ask, “How can that be when they look so small?”

It’s because they are disproportionately large when compared to the relatively small size of the QRS complexes.

Additionally, there is poor anterior R-wave progression and that’s really important because LAD occlusion often (but not always) obliterates the R-waves in the anterior leads. When R-wave progression is obliterated, you know it can’t be early repolarization!

None of this matters, however, because the ECG meets criteria based on the ST-segment elevation in leads I and aVL with reciprocal changes in the inferior leads.

Example 3

hyperacute LAD occlusion with reciprocal changes

Hyperacute T-waves are present in leads V2-V6. In addition, there are hyperacute T-waves in leads I and aVL. There is reciprocal ST-segment depression in leads II, III, and aVF.

Here’s a more impressive case of hyperacute LAD occlusion. Even without ST-segment elevation we can see that the T-waves are broad-based and disproportionately large.

Once again, this acute anterior STEMI “crosses over” to the high lateral leads. Importantly, there are reciprocal changes in the inferior leads to help shore up the diagnosis!

Example 4

hyperacute LAD occlusion without reciprocal changes

The T-waves are hyperacute in leads V2-V6. There is ST-segment elevation in leads V4 and V5. However, there are no reciprocal changes to help shore up the diagnosis!

In this case the T-waves are appear disproportionately large in leads V2-V6. There is 1.5 mm of ST-segment elevation in lead V4 and 1 mm of ST-segment elevation in lead V5. Is this LAD occlusion?

The answer is yes!

However, in this case we don’t have the comfort of ST-segment elevation in the high lateral leads or reciprocal ST-segment depression in the inferior leads to shore up the diagnosis.

What we do have is poor anterior R-wave progression! That lets us know it can’t be early repolarization.

In this case, the patient was quite sick, with typical signs and symptoms, so the pre-test probability was high, which helps with the diagnosis. But what if you’re still not sure?

If you’re a paramedic, by obtaining a 12-lead ECG with the first set of vital signs, and not waiting until the patient is in the back of the ambulance, it gives you “another bite at the apple” before you leave the scene.

Changes on serially obtained 12-lead ECGs suggest the dynamic myocardial oxygen supply vs. demand characteristics of true ACS.

Further Reading

Acute Anterior STEMI: A Challenging Diagnosis!

Early Repolarization or LAD Occlusion?

New Exertional Dyspnea and Subtle ECG Signs of LAD Occlusion

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Tom Bouthillet
Tom Bouthillet - 25 posts

Tom Bouthillet (@tbouthillet) is Editor-in-Chief of ECGMedicalTraining.com (@ECGTraining) and Fire Captain/Paramedic in South Carolina where he is the Emergency Cardiac Care Program Manager and the STEMI and CARES Site Coordinator of his fire department.

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