Wednesday, 17 September 2014

ECG of the Week - 15th September 2014 - Interpretation

This week's ECG is an old one from my collection.
It's from a 75yr old female. I don't have any other clinical information on this case unfortunately.




Click to enlarge

Rate:
  • ~145 bpm
Rhythm:
  • Subtle irregularity in rate
    • Periods of fixed rate of 150 bpm leads V1-3
    • Periods of rate change best seen in lead V6
  • Nil p waves seen
Axis:
  • LAD
Intervals:
  • QRS - Prolonged (120-140ms)
  • QT - 400ms (QTc Bazette 380-400 ms)
Segments:
  • Discordant ST segment / T wave changes

Additional:

  • LBBB morphology
    • Sgarbossa negative
  • Subtle change in QRS morphology best seen V4-6 as rate changes
Interpretation:

  • Wide Complex Tachycardia with LBBB morphology and left axis deviation

So what are the differentials ?

One of our electrophysiologists has looked at this ECG and had these comments.

  • SVT - with either baseline LBBB, would need old ECG's to compare, or aberrancy / rate related block.
    • Most likely mechanism is atrial tachycardia or atrial flutter with 2:1 block with slower variable block at start / end of rhythm strip.
  • VT - bundle branch re-entry
  • Antidromic AV re-entry tachycardia with atriofascicular pathway
  • Pacemaker mediated tachycardia - no obvious pacing spikes but these aren't always seen as in this case from Ed Burns 

Dr Razak has also highlighted some excellent resources on this ECG diagnostic challenge:

  • Neiger JS, Trohman RG. Differential diagnosis of tachycardia with a typical left bundle branch block morphology. World J Cardiol. 2011 May 26;3(5):127-34. PMID: 21666813 Full text here.
  • Sousa PA, Pereira S, Candeias R, de Jesus I. The value of electrocardiography for differential diagnosis in wide QRS complex tachycardia. Rev Port Cardiol. 2014 Mar;33(3):165-73. PMID: 24656320 Full text here

But remember it's all about the patient

  • What symptoms does the patient have ?
  • Do they have signs of clinical compromise ?
  • Do you need to do something now ?



References / Further Reading

Life in the Fast Lane

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