Question

Why right leg is always taken as a reference electrode in ecg?

Answer 1

As with skeletal muscle, electrical activation of the heart is required for the mechanical activation of the heart. The electrical activation of the heart can be picked up (detected) using skin electrodes strategically placed on the body. The placement of these electrodes gives us the leads we use in recording an ECG. You can move through this part of the tutorial as written or you can use the links below to jump to certain parts of the description.

The standard limb (bipolar) leads
The augmented unipolar leads
The chest leads
The first sets of leads developed were the standard limb leads, also known as the bipolar leads. In the standard limb leads, the electrodes were placed on the wrists and ankles of the limbs (a good bony place- that's nice because there's no muscle there to generate action potentials that obscure the heart's activity). Both arms and the left leg were used as active leads (i.e. they became one of the poles in our recording), while the right leg was used as a ground (and still is). With time, we recognized that the same recording could be made by placing the electrode at the shoulders and hips (and with less opportunity for noise to interfere with our recordings).