Case 4: A 57 yr old woman is seen urgently for chest pain of two hours duration. The pain is mild, continuous, aching and localized to the left upper chest and shoulder. No previous cardiovascular problems.
Stuart A. Winston, D.O.
Michael H. Lehmann, M.D.
Richard D. Judge, M.D.
Does this ECG suggest myocardial ischemia or subendocardial injury? If so, what location? Thought 2:
What important intervention is indicated?
The answer to above question is No, this ECG doesn't suggest myocardial ischemia or subendocardial injury and important intervention is to Repeat ECG with appropriate lead placement.
There is symmetrical T-wave inversion in Leads II, III and aVF in this ECG. Ordinarily this would suggest ischemia localized to the inferior wall. However, we've gotten a little tricky here and would like you to note two important, subtle observations.
First of all, notice aVR. The P wave is upright, the QRS is positive and the T wave is upright. This is almost never the case. In aVR all deflections are usually negative because of the orientation of the lead directly above the cavity of the heart. In this tracing aVR just doesn't look right.
Secondly, lead aVF looks exactly like an aVR pattern: P, QRS, and T are all negative.
In this ECG the technician inadvertently reversed leads aVF and aVR. Lead II is affected since it is the instantaneous difference between aVF and aVR (II = aVF - aVR) and also Lead III is likewise affected
(III = aVF -aVL). So now the erroneous negative T wave in aVF also occurs in Leads II and III and gives a pattern consistent with ischemia. The negative P waves in II, III, and aVF erroneously suggest an AV junctional rhythm but this arrhythmia would be benign and is not uncommon in normal individuals. The factitious rhythm here would not cause a severe problem.
The repeat ECG is NORMAL. The patient's chest pain turned out to be musculoskeletal (she had done heavy lifting on the previous evening) and responded to ibuprofen, 400 mg QID.
Busy technicians occasionally get their leads mixed up and this can sometimes result in factitious abnormal patterns. With the limb leads aVR can usually be spotted if it is reversed with aVL or aVF because it is so characteristic: negative everything (P, QRS, and T). Remember, "to err is human" and be on the lookout for lead reversals. They happen from time to time, unfortunately.
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