V2:- Placed in the fourth inter coastal space just to the left of the sternum. For all of these, Wilson common terminal will remain same and only the position of exploring electrode will be changed V1:- Placed in the fourth inter coastal space just to the right of the sternum. Placement of the ECG Leads – chest leads There are six standard and three additional chest leads here we will discuss only six standard chest leads. Exploring electrode connected with positive terminal of the machine is applied on the surface of the chest wall In this case whatever the electrical activity of the heart transmitted along horizontal plane, the exploring electrode will be able to detect the voltages in relation to the indifferent electrode. Making ECG Leads – Chest leads To make an ECG Leads – chest lead, negative terminal of the machine is connected via common wire to the negative electrode at left arm, right arm and left leg with high resistance.

Chest lead basically determines electrical activity of the heart transmitted along the horizontal plane (Transverse/Antero –posterior plane) Vi = Ei – Ie Vi : – Voltage detected by Chest lead Ei :- Potential determined by exploring electrode Ie :- Potential determined by indifferent electrode All the chest leads determine potential differences between exploring electrode and virtual electrode (indifferent electrode), as we know indifferent electrode has almost zero voltage, so potential difference detected by the chest lead is practically equal to voltage detected by exploring electrode. ECG Leads – Precordial Leads ECG Leads – Chest Leads: It is a Unipolar lead having two electrodes, one is positive or exploring electrode applied on the surface of the chest wall and other is indifferent electrode constructed by Wilson central terminal.

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