ECG of Inferior Myocardial Infarction (MI)

by Joseph Alpert, MD

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    00:01 So this is an acute inferior wall myocardial infarction. Notice: let's look at leads 2, 3, and aVF.

    00:09 Remember those are the inferior leads. 2, 3, and aVF, look at the ST elevation that you see here.

    00:16 That ST elevation now marked in the green boxes is quite impressive.

    00:21 It's probably about 3 or 3.5 mm and it suggests this is an inferior MI, right coronary is probably involved or at least in the vast majority of cases.

    00:34 Notice how do we know that this ST elevation is real.

    00:38 We know it because leads 1 and aVL, they are looking form a different direction actually have the opposite.

    00:45 They have ST segment depression.

    00:47 This is a mirror image of the ST elevation in leads 2, 3, and aVF and it tells you this is the real thing.

    00:55 So, this is good evidence that the ST elevation is an acute MI and not from some other cause.

    01:03 Again, here we see another example of an ST elevation in leads 2, 3, and aVF.

    01:11 And by the way, also sometimes we'll do right side at leads that go further out than V1, they give us some image of what's the electrical activity in the right ventricle.

    01:21 You'll notice that there's some ST elevation in so-called lead -- right V4 and that's telling us that the right ventricle is also involved which happens because remember the right coronary artery supplies not only the back of the heart and some of the septum but it also supplies the right ventricle.

    01:38 So, if you have an occlusion particularly at proximal occlusion on the right coronary, you may have some damage to the right ventricle just like you're having inferior wall myocardial infarction.

    01:49 There are -- is ST depression again in leads 1 and aVL. Reciprocal, so-called reciprocal or mirror image change saying this is the real thing.

    01:58 So this is an ST segment elevation in the right precordial lead, implies that there's been some involvement of the right ventricle.

    02:06 When you see right ventricular involvement, it usually means a larger myocardial infarct and the prognosis or the outlook is a little worse. It's more dangerous.

    02:15 Remember I told you that there's prognostic information in the ECG not just diagnostic information.

    About the Lecture

    The lecture ECG of Inferior Myocardial Infarction (MI) by Joseph Alpert, MD is from the course Electrocardiogram (ECG) Interpretation.

    Included Quiz Questions

    1. ST elevation in lead I
    2. ST elevation in lead II
    3. ST elevation in lead III
    4. ST elevation in lead aVF
    5. ST depression in aVL

    Author of lecture ECG of Inferior Myocardial Infarction (MI)

     Joseph Alpert, MD

    Joseph Alpert, MD

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