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In this blog we again look at why serial ECGs are important and how to approach a particular ECG variant, where there may be some ST elevation, but not in contiguous leads. We introduce The South African Flag Sign.
​A 54 yo male presents with left sided chest pain that radiates into his jaw. He has vomited once.
His past medical history includes:

  • Diabetes
  • Hypercholesterolaemia
  • An AMI 10 years ago
  • Hypertension

This is a great case presented recently at EMCORE by Prof Louise Cullen who has allowed me to use her slides here.
​His first ECG is shown below. Describe and interpret the ECG.

Sinus rhythm
Rate 78
Axis: Normal
Narrow complex QRS
ST segments: 

  • ? ST elevation I and aVL
  • T wave inversion lead III

Intervals: Borderline prolonged PR
​Anything else?

Let me ask you this question: Is this a fast rule out candidate? Can we apply ADAPT criteria for rapid rule out? We will need two high sensitivity troponins 2 hours apart and then apply the TIMI Score.
​I can tell you that once he has all these risk factors and has had a previous AMI, he is being referred! This is not a rapid rule out patient.

TIMI Score

The Thrombolysis iMyocardial Infarction Score looks at the likelihood of ischaemic events or mortality in patients with unstable angina or a NSTEMI.
It has been used to risk stratify patients presenting with chest pain. Low risk patients have a TIMI score of < 1.

Without knowing a first troponin- the patient has a TIMI score of 2- He is not for rapid rule-out. He is getting admitted. Let’s look at the case in more detail however and see how it unfolds.
​The TIMI score will also change as we progress.

His first troponin is normal and he has a followup ECG 20 minutes later. Describe and interpret now:

Not much has changed here. Perhaps there is more ST elevation in lead I and certainly aVL. T waves are still inverted in lead III, perhaps some ST depression in III.

The patient has a serial troponin and at 3 hours the troponin is raised, (30ng/L normal is < 20ng/L)
A further ECG is done at 6 hours: Describe and interpret.

Now we see some ST elevation in I and aVL, with ST depression in III.
A further ECG is done and shown below. The Troponin is now raised at 472ng/L.
How is this ECG different?

Perhaps we can now see some ST elevation in I and aVL and even in V2. Perhaps the ST depression in III is a little reduced.
The TIMI Score has now increased to 4 and predicts about a 20% chance of MI or ischaemia or all-cause mortality.

The patient was taken to the cath lab and an occluded Diagonal artery was found, for which he had successful PCI.

So the question here is is, without the 6 hour troponin and the fact that there is no ST elevation in contiguous leads, this might be one of those ECG we miss. We need to look at this particular pattern in the ECG. 

ECG Pattern for High lateral infarct ie 1st Diagonal.
In 2015 Durant et al published a case report of a patient with a characteristic ST elevation in NON contiguous leads, with an acute diagonal occlusion. This is the ECG.

We clearly see the ST elevation in I, aVL and V2 and ST depression in II, III and aVF.
Littman in response to this, discussed the South African Flag sign as a way of memorizing the changes in a high lateral infarct..
The ECG changes were:

  • ST Elevation in I, aVL and V2 and
  • ST Depression in lead III​
We can apply this same sign to out patients ECG as follows:
The SOUTH AFRICAN FLAG SIGN. Remember it, as it can help identify the subtle and non-contiguous changes of a high lateral infarct. For members of the HOMEcardiac bootcamp self study course, go to the section on subtle ischaemia, for more examples.

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