Table 4.1 The lead systems which can be used for recording.


Base-apex lead Right arm electrode (red in UK, white in US) cranial to the right (or left) scapula
Left arm electrode (yellow in UK, black in US) over the apex beat on the left side (level with the olecranon)
Record 'lead I'
Y Lead RA electrode over manubrim
LA electrode over xiphoid
Record 'lead I'
Limb leads and augmented leads
Lead I Potential difference (PD) between left fore leg (+ve) and right fore leg (-ve)
Lead II PD between left hind leg (+ve) and right fore leg (-ve)
Lead III PD between left hind leg (+ve) and left fore leg (-ve)
aVR PD between right fore leg (+ve) and the left fore and left hind legs(-ve)
aVL PD between left fore leg (+ve) and the right fore and left hind legs(-ve)
aVF PD between left hind leg (+ve) and the right and left fore legs(-ve)
Chest leads
CV6LL PD between the left sixth ics, level of the olecranon (-ve) and the central terminal
CV6LU PD between the left sixth ics, level of the shoulder (-ve) and the central terminal
CV6RL PD between the right sixth ics, level of the olecranon (-ve) and the central terminal
CV6RU PD between the right sixth ics, level of the shoulder (-ve) and the central terminal
V3 Approximately=CV6LL
V10 PD between the point of the withers in the mid-line (-ve) and the central terminal, also called a Z lead