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In electrocardiography, electrodes have the typical names of:

  • RA (Right Arm)
  • LA (Left Arm)
  • RL (Right Leg)
  • LL (Left Leg)
  • V1, V2, V3, V4, V5 and V6

What does the V stand for? Is it perhaps from vector, ventricular, or maybe from something else entirely?

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    $\begingroup$ I would imagine it's "ventral", because they're placed on the ventral portion of the body (the front), but that's just a guess. $\endgroup$ – MattDMo Mar 3 '16 at 21:16
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Short answer
V stands for voltage.

Background
The various leads in an ECG montage are shown below:

ECG
ECG electrodes. Source: American Heart Association

I am not an expert in ECGs, but as far as I can see, RA, LA and LL are return electrodes as they are situated far away from the heart. In other words, they act as reference electrodes. RL is the ground, basically to correct for baseline shifts. This leaves the V electrodes, which are the chest leads, or precordial leads, and are situated right above where the action is, i.e., the heart. The ECG is determined between the V electrodes and a distant reference, with a ground added. The V electrodes are the active electrodes, picking up the signal. The others are references and a ground only.

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    $\begingroup$ Thank you - I already had suspected it could be from voltage, but dismissed it, because other electrodes names are anatomy related. The limbs are in fact not all return electrodes, only the RL one is used to actively eliminate common-mode interference. The other three limb electrodes signals are there for differential measurements - they form a "triangle" of signals obtained from LA-RA,LL-RA and LL-LA. $\endgroup$ – Vicente Cunha Mar 3 '16 at 22:52
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As a paramedic who does EKGs every day, I can tell you it stands for "VECTOR" meaning the direction the electrode monitors electricity from the heart.

RA, LA, RL, and LL electrodes are ALL the principle electrodes for monitoring cardiac activity. These are referred to as the "limb leads" and are bipolar leads. The direction these leads monitor is determined by the polarity of the lead, which CAN change. For example, with Lead I the right shoulder is negative and the left shoulder is positive; but in Lead III the left shoulder is negative while the left leg is positive. Electricity flows from negative to positive. When it flows towards the positive electrode, the deflection on the EKG is upward. When it flows away from the negative electrode the deflection on the EKG is downward.

The augmented vector leads are so-called because they have one positive electrode and the negative electrode is augmented. These are aVR, aVL and aVF where R, L and F stand for Right, Left, and Foot respectively. The V stands for vector here. In aVR, the left leg lead and left shoulder lead BOTH provide the negative pole for the EKG while the right shoulder is positive. The augmented vector leads require THREE poles to work: two negative and one positive.

The precordial leads, asked about in the original question, are UNIPOLAR leads. The computer inside the EKG uses the position of all the unipolar leads to create a "dummy" negative point at or near the center of the heart. Each Lead then becomes its own positive, and assumes that it is looking to a negative pole at the center of the heart. These are numbered V1 through V6, and the V stands for Vector. Vector 1, Vector 2, Vector 3 and so on.

One could do an 32-Lead EKG with the 3 Limb Leads, 6 Left Anterior Precordial Leads, 6 Left Posterior Leads, 6 Right Posterior Leads and 6 Left Precordial Leads. It is possible to also do a 64-Lead EKG. But the most common arrangements are 3, 4, 12, and 15 Lead EKGs.

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Very likely it means Unipolar. Please note only unipolar leads aVL, aVR, aVF, and all precordial leads have the letter V. They are all unipolar. Long time ago, the "U" may have been misspeled as "V".

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