Wednesday, 25 May 2016

ECG of the Week - 23rd May 2016 - Interpretation

The following ECG is from a 50 yr old male who was referred in from his GP with a 2 week history of dysponea and myalgia. The GP was concerned regarding an old inferior myocardial infarction.




Click to enlarge

Rate:
  • 60
Rhythm:
  • Regular
  • Sinus rhythm
Axis:
  • Left axis deviation
Intervals:
  • PR - Short (~100-110ms)
  • QRS - Prolonged (140ms)
  • QT - 400ms (QTc Bazette 380-400 ms)
Segments:
  • ST Elevation leads III, aVF
  • ST Depression leads aVL, V5-6 (subtle)
Additional:

  • Delta waves
  • Negative delta wave leads III, aVF
    • 'Pseudo-infarction' pattern
    • Secondary to pre-excitation rather than prior ischaemia
    • Occurs in up to 70% of WPW

Interpretation:

  • Pre-excitation 
    • AP location posteroseptal tricuspid annulus / coronary sinus ostium
    • Axis abnormality, inferior 'Q' waves secondary to pre-excitation
    • ST segment changes are also likely secondary to pre-excitation but comparison with old ECG's and serial ECG's are essential if acute ischaemia is suspected.
    • Please check out the post, link below, from Dr Smith for examples of pre-excitation with and without acute ischaemia


A must read post

I'd encourage all our readers to look at this post from Dr Smith with some great examples of WPW with and without superimposed ischaemia:

Accessory Pathway Location

There are a number of algorithms that can be used to estimate the location of the accessory pathway (AP). Many of these algorithms can be found in smartphone apps, I use EP Mobile which contains the following algorithms:
  • Arruda Algorithm
  • Milstein Algorithm
  • Modified Arruda Algorithm
You can find an overview of each of these algorithms at ECGpedia's WPW page.

What are you going to tell your patient ?

I've put some links here to various patient information resources for WPW, I have not vetted or reviewed all these links but have chosen those from government / institutional sites.

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.