Wednesday, 20 March 2013

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.