ECG of the Week - 18th March 2013 - Interpretation

For those of you at SMACC 2013 (Twitter #SMACC2013) this one will be familiar.

 

These ECGs are from a 58yr old male seen in a rural setting, approximately ~2500 km from the nearest tertiary centre.

 

He c/o intermittent atypical chest pain for several weeks without any cardiac risk factors.

At the clinic serial ECGs were performed and are below.

• What do you think of the ECGs ?
• What advice would you give assuming you were the clinician at the tertiary receiving hospital who was contacted regarding this case ?

 

 

First ECG
Click to enlarge

Second ECG
Click to enlarge

ECG 1
Rate:

• 84

Rhythm:

• Regular
• Sinus Rhythm

Axis:

• Normal (70 deg)

Intervals:

• PR - Normal (~160-200ms)
• QRS - Normal (80ms)
• QT - 340ms (QTc Bazette ~ 390 ms)

Segments:

• Slight Saddling ST segments leads II, III, aVF

ECG 2

Rate:

• 66

Rhythm:

• Regular
• Sinus Rhythm

Axis:

• Normal (-15 deg)

Intervals:

• PR - Normal (~180 ms)
• QRS - Normal (80ms)
• QT - 360ms (QTc Bazette ~ 360 ms)

Segments:

• Slight Saddling ST segments leads I, aVL

Additional:

• T Wave Inversion Leads III, aVF

Interpretation:

• This ECG was interpreted as having dynamic ST change ? ACS.
• The patient was anti-coagulated and transferred by air, ~2500 km, to a tertiary centre for further Mx.

 But let's look again:

• As those of you who have read the comments for this ECG will realise the answer is somewhat less pathological.
• There is an axis change between the 2 ECGs which is a little odd
• Look at the complexes in leads III and you can see not only has the T wave become inverted but so has the P wave and QRS complex

Click to enlarge

• Compare leads aVL & aVF between the two ECGs and we can see these leads have been swapped

Click to enlarge

• The ECG changes are due to a LA / LL lead reversal

• As Christopher has pointed out this results in:
• Leads aVL & aVF swap places
• Leads I & II swap places
• Lead III becomes completely inverted
• Lead aVR remains unchanged
• No change in the precordial leads

References / Further Reading

 

Life in the Fast Lane

• Limb Lead Reversals here

Textbook

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