| A | B |
|---|
| precordial leads | unipolar leads |
| chest sensors | precordial or unipolar leads |
| V1 | fourth intercostal space at right margin of sternum |
| V2 | fourth intercostal space at the left margin of the sternum |
| V3 | midway point between V2 and V4 |
| V4 | fifth intercostal space at the midclavicular line |
| V5 | left axillary fold and same horizontal line as V4 |
| V6 | left mid axillary and same horizontal line as V4 and V5 |
