Saturday, 13 December 2014

ECG of the Week - 8th December 2014 - Interpretation

This ECG is from a 45 yr old male presenting with 3 days of chest pain. He has no significant past medical history.
Check out the comments from our original post here.

Click to enlarge
  • 66 bpm
  • Regular
  • Sinus rhythm
  • RAD
  • PR - Normal (120ms)
  • QRS - Normal (80ms)
  • QT - 400ms (QTc Bazette 420 ms)

  • Normal


  • T wave inversion leads I, aVL, V1
  • Negative P waves lead I, aVL
  • Notched P wave inferior leads
  • Q waves infero-lateral leads (leads II, III, aVF, V4-6)
    • Narrow Q waves
    • Depth ~2 mm but maximal in V5 at 3mm. All <25% of QRS voltage
  • Early R wave transition


  • RA-LA lead reversal
  • Infero-lateral Q waves
    • Normal variant vs structural disease

The presence of complete inversion (P-QRS-T) of any lead, expect aVR, should alert to potential lead reversal as should an ECG with abnormal axis. 
RA-LA is probably the most commonly encountered lead misplacement and results in:

  • Inversion of lead I
    • With resultant RAD, assuming native axis is normal
  • Leads II & III switch places
  • Leads aVR & aVL switch places

We've had multiple examples of lead reversals in some of our previous cases listed below.
More examples of RA-LA lead reversal
An unusual lead reversal, RA-RL and LA-LL.

A cautionary case of LA-LL reversal

This is a case of dextrocardia which also results in an apparent RA-LA reversal

For a complete review of all lead reversal possibilities check out this extensive review at Life in the Fast Lane:

References / Further Reading

  • Chan TC, Brady WJ, Harrigan RA, Ornato JP, Rosen P. ECG in Emergency Medicine and Acute Care. Elsevier Mosby 2005.

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