The recommended 3-wire ECG lead placement is as follows. Place RA (white) electrode under right clavicle, mid-clavicular line within the rib cage frame. Place LA (black) electrode under left clavicle, mid-clavicular line within the rib cage frame.
|V1||4th Intercostal space to the right of the sternum|
|V2||4th Intercostal space to the left of the sternum|
|V3||Midway between V2 and V4|
|V4||5th Intercostal space at the midclavicular line|
To properly record a 12-lead ECG, it is important to have the patient lying comfortably with the wrist close to but not touching the trunk. The limb electrodes should be placed on the right and left wrists and the right and left ankle.
Precordial Lead Placement
V1 is placed to the right of the sternal border, and V2 is placed at the left of the sternal border. Next, V4 should be placed before V3. V4 should be placed in the fifth intercostal space in the midclavicular line (as if drawing a line downwards from the centre of the patient’s clavicle).
For females, place the leads under the breast tissue. You may need to lift and clean the skin underneath the breast to get a clear tracing. A quality 12-lead ECG has a smooth, flat baseline (called the isoelectric line).
|RA placement||WHITE directly below the clavicle and near the right shoulder.|
|RL placement||GREEN on the right lower abdomen.|
|LL placement||RED on the left lower abdomen.|
The most commonly used lead is lead II – a bipolar lead with electrodes on the right arm and left leg. This is the most useful lead for detecting cardiac arrhythmias as it lies close to the cardiac axis (the overall direction of electrical movement) and allows the best view of P and R waves.
ECG paper is marked with a grid of small and large squares. Each small square represents 40 milliseconds (ms) in time along the horizontal axis and each larger square contains 5 small squares, thus representing 200 ms. Standard paper speeds and square markings allow easy measurement of cardiac timing intervals.
In the lead II configuration, the positive electrode is on the left leg and the negative electrode is on the right arm. Lead III has the positive electrode on the left leg and the negative electrode on the left arm.
|Label||Meaning of label||Position of lead on body|
|AVr||Augmented vector right||Right wrist|
|AVL||Augmented vector left||Left wrist|
|AVf||Augmented vector foot||Left foot|
If you’re using AHA’s system, use this mnemonic to easily recall limb electrode placement: smoke over fire (black lead above the red lead) snow over grass (white lead above the green lead)
They are summarized as follows: Lead I: Right arm-negative, Left arm-positive. Records electrical differences between the left and right arm electrodes. Lead II: Right arm-negative, Left leg-positive. Records electrical difference between the left leg and right arm electrodes.
Small pads or patches (electrodes) will be placed, like stickers, on your skin on each arm and leg and on your chest. The electrodes are hooked to a machine that traces your heart activity onto a paper. During the test, lie very still and breathe normally. Do not talk during the test.
The precordial leads, or V leads, represent the heart’s orientation on a transverse plane, providing a three- dimensional view (see Precordial Views). They are placed anatom ically over areas of the left ventricle. 1 Like the augmented leads, the precordial leads are unipolar with an electrically neutral center.
The position for V4 is in the 5th intercostal space , in line with the middle of the clavicle (mid-clavicular). V3 sits midway between V2 and V4. Follow the 5th intercostal space to the left until your fingers are immediately below the beginning of the axilla, or under-arm area. This is the position for V5.
The aVR is often neglected lead. It is an unipolar lead facing the right superior surface. As all the depolarisations are going away from lead aVR, all waves are negative in aVR (P, QRS, T) in normal sinus rhythm.
These leads view the high lateral wall of the left ventricle. I & aVL Lateral Wall Leads V5 and V6 are positioned on the left lateral chest and view the lower lateral wall of the left ventricle. Since Leads 1, aVL, V5 and V6 all view the lateral wall of the left ventricle they are considered contiguous.
A plate electrode that exposes no less than 2 square feet (0.186 m2) of surface to exterior soil shall be considered as a grounding electrode. Electrodes of iron or steel plates shall be at least 1⁄4 inch (6.4mm) in thickness.
Multiple lead monitoring is superior to single lead monitoring. If two leads are available, V1 and lead III or aVF (or a limb lead with maximal ST segment displacement) are good choices. If three leads are available, leads V1, III, and aVF are the best choices.
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