“Switched” Precordial Leads
To the Editor:
In the article on “switched” precordial leads by Hurst,1 an ECG is shown in which leads V1 and V3 have been switched. Hurst states that the V1 lead wire was erroneously plugged into the V3 receptacle, and the lead wire labeled V3 was erroneously plugged into the V1 receptacle.
It is important to note, however, that a V lead in Wilson terminology is a V lead, regardless of where the exploring electrode is placed [V lead=exploring electrode on chest minus central terminal (R+L+F)/3], where R indicates right arm, L indicates left arm, and F indicates left leg. Only the subscript (1, 2, 3, 4, 5, or 6) specifies its location.
Therefore, if lead V3 is placed at the V1 position, the ECG should be that of V1. Obviously, it is not, and Hurst did not address this. The reason why it isn’t resides in the design and circuitry of the apparatus. Regardless of the label on the lead wire electrode, the data printed are always labeled according to the channel coming into the acquisition module. For example, if the electrode wire labeled V6 is plugged into the V1 socket, the data will be printed out as lead V1 but with complexes of lead V6.
Therefore, Hurst’s admonition that today’s equipment requires that leads be placed specifically as labeled should be emphasized, because the socket labeled V3 will always be the same in any of the usual chest locations, rather than indicative of the p potential underneath the exploring electrode.
- Copyright © 2001 by American Heart Association
I agree with Zatuchni and Elko’s comments and appreciate their contribution to the solution of the problem.