You ever have a tough time visualizing P waves on EKGs? Have no fear, a Lewis Lead EKG might just be the thing you need!

The Lewis Lead (aka S5) is a modified EKG obtained in a manner that basically triangulates atrial activity to help make the p-waves of your EKG more prominent. Lead placement includes the RA lead placed on the manubrium, the LA lead placed at the 5th intercostal space at the R sternal border, a LL lead placed at the right lower costal margin, and +/- the RL lead placed that the right leg.


In this configuration, lead I will travel directly over the atria, maximizing the size of the P wave

Lewis Lead (diagram 2)


Why or when would you ever want to do this?

  • EKGs with questionable P waves — those such as atrial fibrillation/flutter, wide complex tachycardia

What does this even look like?

regular EKG
Regular 12-Lead; Leads I & II
Lewis Lead I
Lewis Lead I
Lewis Lead II
Lewis Lead II

And there you have it folks! Feel free to throw that one at your next VT vs AFib RVR with aberrency!



The Lewis Lead

EMCrit Wee: The Lewis Lead and a course in ECGs with Christopher Watford