V1 - V6 Leads

Chest leads provide another view of the heart. The major difference is that the negative leads are imaginary and not real physical leads. The ECG machine provides a ground (or negative lead) inside the machine for each positive lead. These leads are called unipolar and work as if each positive lead had an imaginary negative lead at the back of the patient directly in line with the positive lead on the chest and passing through the AV node. The chest or V leads provide information about electrical activity in a horizontal plane with leads acting like the spokes of a wheel around a hub at the AV node.

Vl & V2 - The positive electrode for these leads is adjacent to the sternum at about the level of the atria, hence the P-waves are prominent but the R-waves are negative deflections.

V3, V4, V5 & V6 - In these lead positions, the positive charges follow a progressively longer path through the ventricles (V3-V5) where normally at V5 the charge traverses the ventricular septum (hence the greatest amount of tissue and greatest positive deflection). At V6, the positive deflection normally begins to shorten again. These chest leads can help determine alterations in axial inclinations of the heart.

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