The 3 lead ECG is generally used in pre-hospital care, for continuous monitoring of a patient having had some form of a cardiac event.


3 lead is deployed because it is simple to use and requires a much less sensitive machine, and capable of picking up the specific electrical rhythm, or lack of, in the heart. It will do so without too much interference as a 12 lead ECG would.

3 lead ECG is non-diagnostic, thus does not provide a clear view of the entire heart. Instead, it provides a basic view of the electrical pathway of the heart triangulated between the 3 leads.

Einthoven’s Triangle 3 lead placementEinthoven’s Triangle is formed when the three ECG leads are placed on the patient.

A red lead is placed on the right wrist or shoulder- known as AVr

A yellow lead is placed on left wrist or shoulder- known as AVl.

A green lead is placed on the ankle or left lower abdomen- known as AVf

Information gathered between these leads is known as “bipolar”. It is represented on the ECG as 3 “bipolar” leads.

When looking at the ECG chart these are shown as I, II, II

information between AVr and AVl is known as lead l.
Information between AVr and AVf is known as lead ll
Information between AVl and AVf is known as lead lll

A first aider would only place leads where directed by the paramedic and not based on assumption.

3 Lead ECG placement