ECG of the Week – 1st January 2018 – Interpretation

The following ECG’s are from a 23 yr old female with a known history of pre-excitation and prior ablation.

Click to enlarge

Key features
  • Sinus tachycardia ~120 bpm
  • P waves visible in leads I, II, V1
  • PR normal ~180ms
  • RBBB morphology
  • Relatively pronounced ST/ T wave changes in right precordial leads
  • Sinus tachycardia
  • Nil evidence of pre-excitation / AP conduction
  • RBBB
  • ST / T changes could be secondary to RBBB but may reflect additional abnormality e.g hyperventilation, ischaemia etc.
Click to enlarge

Key features:

  • Rate 100 bpm
  • Preceding P waves with short pr
  • Typical LBBB morphology
  • Initial deflection in QRS appears slurred ? associated delta wave

Now things get complicated ! I sent these ECG’s to one of our blog co-authors and electrophysiologist. I don’t have a great deal of clinical information on the case regarding this presentation or more importantly their prior EP findings and ablation technique. 
There are a number of differentials for these second ECG findings including:

1. SVT with LBBB morphology
  • Atrial tachycardia with maximal pre-excitation utilising most likely right sided accessory pathway given negative delta wave V1
  • AV node re-entry with maximal pre-excitation utilising most likely right sided accessory pathway
2. Ventricular tachycardia
  • Emanating from RV septum (mid to high level)
  • Bundle branch re-entrant VT –> ? related to prior ablation
3. Pre-excited tachycardia 

  • Atriofasciscular pathway with AV re-entrant tachycardia
  • Nodofascicular pathway with AV re-entrant tachycardia
  • Nodoventricular pathway with AV re-entrant tachycardia
  • Pathway to pathway re-entrant tachycardia
Atriofascicular and nodoventricular pathways are something we don’t encounter often in clinical practice and are much rarer than those patients with WPW accessory pathways. You can read more about them in the following articles:

References / Further Reading

Life in the Fast Lane


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

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