Wednesday, 15 March 2017

ECG of the Week - 13th March 2017 - Interpretation

This ECG is from a 50 yr old male who presented with 2 hours of central chest pain. He has a history of palpitations and is a smoker.


  
Click to enlarge
Rate:
  • 72 bpm
Rhythm:
  • Regular 
  • Sinus rhythm 
Axis:
  • Normal
Intervals:
  • PR - Short (~100ms)
  • QRS - Prolonged (110-120ms)
Segments:
  • ST Elevation II, III, aVF, V5-6
  • ST Depression lead aVL
Additional:
  • Delta wave
  • Biphasic T wave V2-4
  • T Inversion lead aVL
Interpretation:
  • Wolff-Parkinson-White / Pre-excitation
    • Short pr
    • Delta wave
    • QRS Prolongation
    • Type 'A' Pattern / Left sided accessory pathway
    • Left posterior AP using Modified Arruda Algorthm
  • ST changes on single ECG could be secondary to pre-excitation vs ACS
What happened ?

This patient had no old ECG's for comparison and had never been given a diagnosis of pre-excitation before today. The nature and history of the chest pain was suspicious of myocardial ischaemia. The patient was pain-free following initial ED treatment and serial ECG's did not show dynamic changes. He had raised troponins, peak trop I 0.28 ug/L, and underwent angiography which showed:
  • LM: Normal
  • LAD: Mild - mod / mild disease
  • Cx: Normal
  • RCA: 70% mid stenosis --> PCI with BMS
Post stent echo showed:
  • Normal LV size and function
  • Basal posterior wall motion abnormality due to pre-excitation
  • Normal RV size and function
The patient was commenced on DAPT, statin and beta-blocker therapy with planned electro-physiologist follow-up for EPS +/- ablation.

This case highlights the challenges of assessing for acute ischaemia in the setting of pre-excitation in this scenario clinical suspicion, serial ECG's and comparison with old ECG's are paramount. This are no 'rules' we can apply in these scenarios to differentiate acute ischaemia from the abnormalities seen due to pre-excitation.

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.

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.