The Lewis Lead: A lead placement to see oscillations

What is the rhythm?

Figure 1 - ECG case

If you suspect there are "extra" P waves that are not seen on the surface ECG, you can use the Lewis lead configuration (Figure 2).

Figure 2 - Lewis lead configuration 

This is done by placing the right arm electrode applied to the right side of the sternum at the RIGHT second intercostal space and the left arm electrode applied to the RIGHT fourth intercostal space.  This configuration was developed by Sir Thomas Lewis in the 1900's to magnify atrial oscillations during atrial fibrillation.

In the case presented, after changing the configuration to Lewis lead placement, flutter waves are best seen (especially in lead II).

Figure 3 - Flutter waves are better seen after Lewis lead configuration

Figure 4 - Usual lead placement vs. Lewis lead configuration

Here is the cropped version (Figure 4 - A - usual lead placement and B - Lewis lead configuration).

Interpretation: Atrial flutter

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