Modified Chest Leads (was: Modified Leads "On the Ice")

Occasionally I receive emails from readers who ask various questions or submit interesting ECGs which I sometimes use as case studies on the Prehospital 12-Lead ECG blog.

Back in November I received an email from a reader who wrote:

Hello! I’m currently in Antarctica on a medical support contract. I was issued a 3-lead Lifepak 10 for use at the field camp I’m staffing.

I’m wondering if you know of any way to manipulate/ alter this type of monitor so as to be able to gain V-lead views?

I kind of remember being shown some sort of trick years ago but, someone told me that it was probably demonstrated with a 4-lead monitor.

Any ideas? Many thanks in advance for your help!

Kindest Regards,
Ernie

I wrote him back with the following reply:

Hi, Ernie!

It’s easy. You just put the negative electrode in the position of the left shoulder and the positive electrode in the position of V1 (for example) and the result is MCL-1 (modified chest lead 1) which mimics V1. If you place the positive electrode in the position of V2 it’s MCL-2, and so on.

The fact that it’s a 3-lead is irrelevant because even a 4-lead is technically still a 3-lead. By designating the 4th electrode as the “ground lead” you can view all 3 leads (I, II, and III) at the same time. With a 3-lead you can only view one at a time because the 3rd lead defaults to the ground lead. For example, if you’re viewing lead II with a 3-lead it’s white (negative) to red (positive) and the black becomes the ground lead. If you’re viewing lead III then it’s black (negative) to red (positive) and the white becomes the ground lead.

One final suggestion. If memory serves with a LP10 you have to hold down a button (maybe the print button) continuously until a DIAG appears in the corner of the monitor screen which puts you in a diagnostic frequency response (where the low frequency/high pass filter goes from 1 to 0.05 Hz) so you can record accurate ST-segments. I hope this helps! Thanks for the question. Have a great day! Stay warm! Send pictures too if you get a chance! I’ll put you on my blog! :)

Tom

Well, I just heard back from him yesterday:

Tom,

Not sure if you remember me; I was the guy working in Antarctica that got in touch with you a few months ago to learn how to gain modified chest leads with the LP-10.

Well, I didn’t forget about you. I got home to California a couple of weeks ago, and have been getting caught up on email ever since! As promised, I’ve attached some pictures. You have my full permission to use any of the pics on your blog; I won’t be offended if you don’t use any though – I understand that it would be an odd entry for a blog dedicated to 12 lead education!

While I didn’t have to connect any patients to the LP-10, I was happy that I knew how to gain MCL’s 1 thru 6 if need be. Thanks again for your prompt and informative reply back in November.

Let me know if you have any questions about the pictures, or anything else.

Take Care,
Ernie

Here are the pictures he sent.

Here’s Ernie after a well-deserved haircut!

Thanks, Ernie! I’m glad I could be of assistance! Welcome home.

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