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

Rate:

• Ventricular rate ~96 bpm

Rhythm:

• 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

Axis:

• Normal

Intervals:

• QRS - Normal (100ms)

Segments:

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

Interpretation:

• 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

Rate:

• Atrial rate ~250 bpm
• Ventricular rate ~62 bpm

Rhythm:

• Regular atrial and ventricular activity
• Single PVC at start of rhythm strip

Intervals:

• QRS - Normal (100ms)

Additional:

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

Interpretation:

• 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:

• Bakker AL, Nijkerk G, Groenemeijer BE, Waalewijn RA, Koomen EM, Braam RL, Wellens HJ.The Lewis lead: making recognition of P waves easy during wide QRS complex tachycardia.Circulation. 2009 Jun 23;119(24):e592-3.
• EMCritWee - The Lewis Lead
• Dr Smith's ECG Blog - Wide Complex Tachycardia: Lewis Leads Do Not Differentiate VT from SVT with Aberrancy

References / Further Reading

Life in the Fast Lane

• Atrial tachycardia
• Atrial flutter
• Wenckebach Phenomenon

Textbook

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