ECG Case 105

ECG is from a 70yr old male who presented with chest pain and palpitations.

Vital signs: BP 85/64 RR 20 Sats 98% on 10L/min.

ECG Case 105 LITFL Top 100 EKG

Describe and interpret this ECG



  • 150


  • Regular


  • LAD (~ 80deg)


  • QRS – Prolonged (140ms)
  • QT – 320ms


  • RBBB Morphology
    • Typical morphology


  • Regular Wide Complex Tachycardia
    • Clinical compromise evidence by chest pain and hypotension


General differential diagnosis include:

  • Ventricular Tachycardia
  • SVT with aberrancy
  • SVT with pre-existing conduction delay
  • SVT with pre-excitation
  • Not applicable in this case but don’t forget paced rhythms

But what about this ECG? This ECG is most probably SVT (likely atrial flutter) with RBBB aberrancy as the principle diagnosis. The QRS activation pattern of rapid activation till QRS peak followed by slower activation is classic for RBBB aberrancy. 

The combination of RBBB and LAD (left axis deviation) means the SVT exit is the left posterior fascicle (left mid to basal LV), if this was VT it would be a fascicular VT.

Check out the links below for more on VT vs SVT with aberrancy and also on fascicular VT:

What happened next?

…the patient underwent DC cardioversion in the Emergency Department and his post cardioversion ECG can be interpreted as Top 100 ECG Case 106

TOP 150 ECG Series

Emergency Medicine Specialist MBChB FRCEM FACEM. Medical Education, Cardiology and Web Based Resources | @jjlarkin78 | LinkedIn |


  1. I don’t understand how this is likely SVT – A-flutter. in all of the lateral leads, the deflection is negative, making it, to me, appear to be of ventricular origin. I am 0 for 50 on these things, and when I show these to any cardiologist, I get nothing but different answers between all of them.

  2. The rate of 150 is common in A. Flutter 2:1 Conduction I think.
    I would have thought it was VTach at first glance but im just a humble ambo tech and im sure John knows better!!!

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