ECG 1 - Precordial lead placement.

TIP: To see temporary labels, CLICK on the electrodes on the body.

ECG background.

All myocardial (heart muscle) activity is preceded and driven by ion exchange in the myocites (muscle cells).
Ion exchange results in electrical changes in the muscle cells that can be observed as vectors on an electrocardiogram (amplitude in mV and a positive or negative direction).
An electrical conduction signal moving towards an electode shows a positive curve (above the baseline) on an ECG graph while conduction traveling away from the electrodes will show a negative deflections (below the baseline).
Changes in ECG vectors can be indicative of pathology.
Early identification of such patholohgical changes on an ECG will can help with early intervention and improve health outcomes for patients with cardiovascular disease.

Lead placement:

The 3d graphic on the right shows a standard precordial lead configuration (V1 -V6) on a dummy chest. When we remove the skin and rib cage we can see that leads V1-2 face the anterior wall and septum, leads V3-4 look at the anterior walls of the heart while leads V5-6 give us a lateral perspective of the heart.

In 'Rib View' we can see the rib level placement of the electrodes.

• V1 - 4th intercostal space, to the right of sternum.
• V2 - 4th intercostal space, to the left of sternum.
• V3 - diagonally between V2 and V4.
• V4 - 5th intercostal space in the midclavicular line.
• V5 - same level as V4 in the anteriomid-axillary line.

Typical limb lead placement.