12 Lead ECG Electrode Placement

Great, so the 12 Lead ECG machines have finally been arrived to pre-hospital care (ambulance practice). Is the 12 lead ECG like the 3 lead ECG? No, other than the fact that it basically shows a rough outline of the electrical pathway of heart the similarities basically end there. Where the 3 lead ECG primarily looks at finding basic arrythmias, such as VT, VF and Assystole for the purpose of immediate treatment, and other more minor dysrhythmias, such as AF, SVT, 1,2, and 3rd degree heart blocks, the 12 lead ECG looks at an overall picture of the electrical pathway of the heart, for the purpose of find conduction pathway disturbances that indicate myocardial ischaemia and/or infarction. In particular, In Ambulance Practice, we are looking for acute changes in the ST segment of the ECG (being ST depression or ST elevation in 2 or more contiguous leads of more than 1 mm in the limb leads or 2 mm in the augmented leads.

12 Lead ECG Placement

Okay, so we’re looking for a STEMI (ST elevation myocardial infarction). Where do we place the 12 lead ECG leads? The regular limb leads should be placed on each wrist and each lower limb, while the precordial leads (augmented leads) should be placed as follows:

1. V1 – at the fourth intercostal space to the right of the sternal notch.

2. V2 – at the fourth intercostal space to the left of the sternal notch.

3. V3. Midway between V2 and V4 (this will make sense when you see this later).

4. V4. Fifth intercostal space, mid clavicular line (this roughly corresponds with the left nipple).

5. V5. Left anterior auxillary line at the same horizontal level as V4.

6. V6. Left mid auxillary line at the same horizontal level as V4 and V5.