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:

• http://hqmeded-ecg.blogspot.com.au/2014/07/repost-certain-pattern-of-pseudostemi.html

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.

• Cleveland Clinic - WPW Information
• Better Health Channel (Victoria) - WPW Information
• Medline Plus - WPW Information

References / Further Reading

Life in the Fast Lane

• Pre-Excitation Syndromes

Textbook

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