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.

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Rate:

• 66 bpm

Rhythm:

• Regular
• Sinus rhythm

Axis:

• RAD

Intervals:

• PR - Normal (120ms)
• QRS - Normal (80ms)
• QT - 400ms (QTc Bazette 420 ms)

Segments:

• Normal

Additional:

• 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

Interpretation:

• 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

• ECG of the Week - 27th October 2014 - Interpretation
• ECG of the Week - 9th July 2012 - Interpretation
• ECG of the Week - 10th September 2012 - Interpretation

An unusual lead reversal, RA-RL and LA-LL.

• ECG of the Week - 3rd June 2013 - Interpretation

A cautionary case of LA-LL reversal

• ECG of the Week - 18th March 2013 - Interpretation

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

• ECG of the Week - 17th February 2014 - Interpretation

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

• Limb Lead Reversal Overview - Life in the Fast Lane ECG Library

References / Further Reading

Textbook

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