ECG Case 025
Asymptomatic adult patient. Routine ECG. Describe the ECG.
Describe and interpret this ECG
ECG ANSWER and INTERPRETATION
Main Abnormalities
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.
CLINICAL PEARLS
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.
References
Further Reading
- Wiesbauer F, Kühn P. ECG Mastery: Yellow Belt online course. Understand ECG basics. Medmastery
- Wiesbauer F, Kühn P. ECG Mastery: Blue Belt online course: Become an ECG expert. Medmastery
- Kühn P, Houghton A. ECG Mastery: Black Belt Workshop. Advanced ECG interpretation. Medmastery
- Rawshani A. Clinical ECG Interpretation ECG Waves
- Smith SW. Dr Smith’s ECG blog.
- Wiesbauer F. Little Black Book of ECG Secrets. Medmastery PDF
TOP 100 ECG Series
Emergency Physician in Prehospital and Retrieval Medicine in Sydney, Australia. He has a passion for ECG interpretation and medical education | ECG Library |
MBBS FACEM DDU (Emergency) CCPU. Emergency Physician in Melbourne, Australia. Co-Ultrasound Lead for Emergency Medicine at The Alfred Hospital. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Editor of the LITFL ECG Library.