Thursday, 4 June 2015

ECG of the Week - 1st June 2015 - Interpretation

This week's ECG is from a 65 yr old who presented with palpitations for several hours. Past history of paroxysmal atrial fibrillation. We have two tracing to review - the first is a standard 12-lead ECG and the second is a lead I rhythm strip using a Lewis lead configuration but at standard calibration (10mm/mV & 25mm/s).
Check out the comments on our original post here.

Standard 12-Lead ECG

Standard 12-lead ECG
Click to enlarge

  • Ventricular rate ~96 bpm
  • Regularly irregular
    • Grouped beating pattern
    • 3 successive ventricular complexes then pause
    • R-R shortening before pause although subtle
    • First R-R in group is 540 ms
    • Second R-R in group is 520 ms
  • Atrial activity difficult to see but suggestion in V1-2 of atrial activity
  • Normal
  • QRS - Normal (100ms)

  • ST Depression Leads II, III, aVL V2-6
  • ST Elevation lead aVR 


  • Nil clear sinus activity
  • V1-2 ? atrial tachycardia or flutter waves
  • Grouped beating pattern with subtle R-R shortening suggesting Wenckebach phenomenon
  • Both the above suggest a multi-level block

Lewis Lead 

Rhythm Strip Lead I using Lewis Lead Configuration
Calibration 10mm/mV & 25mm/s
Click to enlarge

  • Atrial rate ~250 bpm
  • Ventricular rate ~62 bpm
  • Regular atrial and ventricular activity
  • Single PVC at start of rhythm strip
  • QRS - Normal (100ms)

  • Subtle variations in atrial activity morphology
  • Flat isoelectric segment
  • Nil evidence of grouped beating or Wenckebach


  • Likely atrial tachycardia with block
  • DDx atrial flutter with block

Lewis Lead

The Lewis lead configuration was first described in 1931 and uses a modified lead placement to assist in the identification of atrial activity. 

You can read more about the Lewis lead and how to perform it in the links below:

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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