The 3 lead ECG is the most commonly used ECG in pre-hospital care and is most regularly utilised in continuous monitoring of the person who has had some form of cardiac event. This is because it is simple to use and requires a much less sensitive machine, therefore it is capable of picking up the specific electrical rhythym (or lack of rhythym) in the heart, without picking up as much arterfact (interference) as a much more detailed 12 lead ECG would.
A 3 lead ECG is considered non-diagnostic, meaning that it does not provide a clear view of the entire heart, but instead a basic view of the electrical pathway of the heart triagulated between the 3 leads.
3 Lead ECG Placement Diagram
The 3 lead ECG is usually simple to use and most brands have a standardized colour coded placement of the 3 electrode leads. Although I’ve recently discovered that the US use a different colour scheme involving the colours red, yellow and green for their electrodes. These are the most common 3 lead ECG placements:
1. Right arm limb lead is white (white goes to the right) – forearm, proximal to the wrist.
2. Left arm limb lead is black and is considered the Earth lead, and is placed at the forearm, proximal to the wrist.
3. Left leg limb lead is red and is placed at the left lower leg, proximal to the ankle.
Please note that, irrespective of the colour codings, the 3 lead ECGs have the name of the electrode, such as RA, LA, and LL. Furthermore, it is important to understand that there is sometimes a fourth limb lead (Right Leg), which is then used as the neutral lead and this leads into the basics for the limb leads used in a 12 lead ECG.