2.4 Inferior Myocardial Infarction on an ECG

Question 1

List the findings on an ECG expected for an inferior ST-elevation myocardial infarction.

Answer 1

1. ST elevation in inferior leads II, III, aVF (green)
2. ST depression (reciprocal changes) in I and aVL, as these are look in ‘another direction’ (red)

Question 2

Explain the prognosis if you found ST elevation on the R ventricular lead of an ECG for an inferior MI.

Answer 2

ST elevation in the R ventricular lead indicates worse prognosis.

It indicates a right ventricular lesion.

The image shows an IMI.

• Green indicates ST elevation in II, III, aVF.
• Red indicates reciprocal ST depression in I and aVL.
• Blue indicates R ventricular lead ST elevation, that is, that that there is a right ventricular lesion.

Question 3

Visualise the vector of injury on a hexaxial diagram of the ECG.

Answer 3

Question 4

What kind of MI is shown?

Answer 4

Acute inferior MI. There is ST elevation in II, III and aVF.

Notice the box shape at the start which is the ‘standardisation’. If calibrated corrected, it should be 10 little boxes high.

Question 5

ECG Case!

A 67-year-old diabetic man with a history of elevated blood cholesterol and hypertension comes to the hospital complaining of feelings of indigestion in his upper abdomen and lower chest. He is sweating and has low blood pressure (96/60 mm Hg). His heart rate is 52 beats per minute.

Look at his ECG. What changes are there and what does he have?

Answer 5

He has ST elevation in II, III and aVF.

There are reciprocal ST depression changes in I and aVL.

He has an inferior MI.

Of note, often low HR and BP are also seen in inferior MI as there is vagal involvement.