Asymptomatic adult patient. Routine ECG. Describe the ECG.
Describe and interpret this ECG
ECG ANSWER and INTERPRETATION
This ECG is a classic example of limb lead misplacement with a left arm / right arm lead reversal:
- Positive P-QRS-T in lead aVR.
- Inverted complexes in leads I and aVL.
- Normal complexes in the precordial leads rules out dextrocardia (compare this to ECG Quiz 024)
The most obvious abnormality on this ECG is the positive QRS complex in aVR. This is unusual and should always prompt a search for additional evidence of limb lead misplacement.
Effects of LA-RA lead reversal
Switching the LA and RA electrodes produces the following effects:
- Lead I becomes inverted.
- Leads II and III switch places.
- Leads aVL and aVR switch places (hence aVR becomes positive, aVL negative).
- Lead aVF remains unchanged
This concept is explained in more detail here.