Tuesday, December 21, 2010

ECG Interpretation Review - #7 (Infarction, ECG Changes, Inferior, Posterior, Lateral, Anterior MI)

QUESTION: Interpret the 12-lead ECG below, obtained from a patient with new-onset severe chest pain.
  • How many abnormal findings can you identify?
  • What areas of the heart are involved?

Figure 1 — ECG from a patient with new-onset chest pain (See text).

INTERPRETATION:  The rhythm is sinus at 75/minute.  All intervals are normal.  We estimate the axis at +60 degrees.  There is no chamber enlargement.
  • Q-R-S-T Changes: There are fairly large Q waves in the inferior leads, and smaller q waves in V5,V6.  Transition occurs normally between leads V3-to-V4 (Did you notice slight loss of R wave fromV2 to V3? )
  • There is hyperacute ST segment elevation in leads III and aVF.  By the concept of "patterns-of-leads" (ie, simultaneously looking at all leads in a given lead group) — there is probably also some ST elevation in lead II.  There are reciprocal changes (ST depression/T wave inversion) in the anterolateral leads.
CLINICAL IMPRESSION:  This ECG suggests acute inferior MI, with development of Q waves, ST elevation, and extensive reciprocal changes.  List #5 (Figure 2) suggests that in addition to reciprocal changes, the T wave inversion in leads V2,V3 could also be due to associated posterior MI and/or concomitant anterior ischemia (Note how the depressed ST segment pattern in leads I and aVL is virtually the mirror image of the ST elevation in leads III and aVF — ergo, true "reciprocal" changes!).

Figure 2 - Causes of Anterior ST Depression with Inferior MI.

ADDITIONAL POINTS:  Given the history (new-onset chest pain) and the ECG picture seen in Figure 1 - this patient is clearly a good potential candidate for acute intervention.
  • Finally — Subtle but real loss of R wave (from V2-to-V3) could be due to lead placement error or it could reflect loss of anterior forces from acute MI.


  1. Thanks for the post... Would you consider the possibility of RV infarction here? STe 3>2, isoelectric ST in v1 with STd in following leads, also subtle STe in aVR..

    1. Acute RV involvement is possible here because of the flat ST segment in lead V1 (instead of being depressed) — but not really because of the other factors you listed. The way to know would be to get a right-sided ECG ...