5-Lead ECG Placement and Cardiac Monitoring

CPD
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Published: 21 April 2020

In order to accurately and correctly assess a patient using 5-lead monitoring, it is necessary to understand how ECG works, know how to prepare the patient and follow the standardised system for electrodes and their placement.

An electrocardiogram (ECG) is a non-invasive method of monitoring the electrophysiology of the heart (Mayo Clinic 2020).

While ECG is commonly used across a variety of medical settings, it plays a particularly important role in the haemodynamic assessment of ICU patients (Liverpool Hospital 2014).

All ICU patients generally require continuous ECG monitoring if clinically unstable. Continuous ECG monitoring can improve the detection of clinical deterioration (Liverpool Hospital 2014; Moss et al. 2017).

How does ECG Work?

ECG involves the placement of electrodes on to the patient’s torso and/or limbs. The electrodes are connected to an electrocardiograph, which displays a pictorial representation of the patient’s cardiac activity (Liverpool Hospital 2014; Mayo Clinic 2020).

The waves detected and visually displayed through ECG illustrate the sequence of depolarisation (positive current) and repolarisation (negative current) generated by action potentials (electrical impulses) in the heart (Liverpool Hospital 2014; Klabunde 2019).

In ICU settings, ECG is generally used for continuous monitoring of the patient’s heart rate and the detection of any potentially fatal cardiac abnormalities such as arrhythmias, but may also serve a diagnostic purpose (Gandhi & Lewis 2016).

ecg monitor
"Hôpital de LaSalle, 8585, terrasse Champlain, LaSalle (Montréal), Québec" by Jeangagnon is licensed under CC BY-SA 4.0.

What is 5-Lead ECG?

ECG measures the electrical activity of the heart from several leads (viewpoints) in order to construct a three-dimensional picture of the patient’s cardiac function using vertical and horizontal planes (HEARTe 2017; Cables and Sensors 2016).

Each lead has its own code name and represents the voltage difference between two electrodes. There are two types of leads:

Lead type Leads included How they work
Bipolar leads (i.e. standard limb leads) I, II, III Measure the voltage difference between one positive electrode and one negative electrode.
Unipolar leads (i.e. augmented leads and chest leads)
  • aVR, aVL, aVF (augmented limb leads)
  • V1, V2, V3, V4, V5, V6 (chest leads)
Have a single positive electrode and use a combination of the other electrodes as a composite negative electrode.

(Cables and Sensors 2016; Klabunde 2016)

Commonly used lead systems include:

  • 3-lead monitoring, which uses 3 electrodes on the torso;
  • 5-lead monitoring, which uses 5 electrodes on the torso; and
  • 12-lead monitoring, which uses 10 electrodes on the torso and limbs.

(Cadogan 2019)

12-lead monitoring is generally considered the standard form of ECG and provides the most information, however, it is not always feasible. Limb movement, tremor, anxiety and cold extremities may interfere with ECG readings, causing them to be poor quality and consequently more difficult to interpret (Khan 2015).

As a result, torso leads are preferable as they allow for better quality ECGs. 3 and 5-lead monitoring take electrodes that are used for the limbs in 12-lead monitoring and instead place them on the chest wall in order to reduce artifacts (ECG signals that are from sources other than the heart) caused by patient movement (Khan 2015; Sampson 2018; Phillips 2008).

5-lead monitoring is the same as 3-lead monitoring, but with two additional electrodes that enable the monitoring of extra leads and help improve ST elevation readings (Cables and Sensors 2016). It is able to monitor the leads I, II, III, aVR, aVL, aVF and V (Phillips 2008).

ecg waveform
The normal sinus rhythmm, as seen in 12-lead monitoring.

5-Lead Placement

Correct placement of electrodes is crucial.

The placement of electrodes for ECG monitoring is standardised to ensure that the information gathered is accurate and can be compared with records from other occasions. To ensure accurate results, the patient must also be correctly prepared both physically and psychologically (Walker 2019).

Poor electrode placement can result in mistaken interpretation, and then possible misdiagnosis, patient mismanagement and inappropriate procedures (Khunti 2013).

ECG electrodes are colour-coded, and each is identified by a specific code that refers to its intended placement. There are two coding systems currently in use:

  1. American Heart Association (AHA) system; and
  2. International Electrotechnical Commission (IEC) system.

Both systems are described in the table below.

Code (AHA) Code (IEC) Location Colour (AHA) Colour (IEC)
RA R Right arm (inner wrist) White Red
RL N Right leg (inner ankle) Green Black
LA L Left arm (inner wrist) Black Yellow
LL F Left leg (inner ankle) Red Green
V C Chest Brown White

(Table adapted from Walker 2019; Cables and Sensors 2016; PanSW 2013)

Method of 5-Lead Placement

Note: The following guide uses the AHA system.

  1. Prepare the patient physically and psychologically.
    • Explain the procedure in detail.
    • Obtain informed consent.
    • Maintain patient dignity (i.e. give them privacy).
    • Ensure the patient is in the supine position.
    • Ensure the patient is comfortable and relaxed.

  2. Perform appropriate skin preparation.
    • Select sites away from large muscle groups. Sites should be flat with intact skin.
    • Dry, dead epidermal layers of skin should be removed. Natural oils and dirt should also be removed.
    • Shave hair at the allocated sites.
    • Wash sites thoroughly with soap and water. Rinse and dry well.

  3. Place the electrodes.
    • The lead wires should be attached before the electrodes are applied.
    • The electrodes should be applied by pressing around the edges instead of in the centre (this spreads the gel out and creates air pockets).
RA placement WHITE directly below the clavicle and near the right shoulder.
LA placement BLACK directly below the clavicle and near the left shoulder.
RL placement GREEN on the right lower abdomen.
LL placement RED on the left lower abdomen.
V placement BROWN on the chest, the position depends on your required lead selection (4th intercostal space, the right side of the sternum).
ecg positions
Correct placement of electrodes is crucial to ensure that the information gathered is accurate.
  1. Connect lead wires to the ECG connector and ensure the waveform is visible on the monitor.

  2. Ensure all monitor alarms are on and audible.

  3. Always check with a colleague if unsure.

  4. Replace the electrodes at least daily, or more frequently as required.

(Liverpool Hospital 2014; QLD Health 2013; Phillips 2008)

Possible Complications

While 5-lead monitoring can provide an adequate amount of information, if something of concern is noted, such as a cardiac arrhythmia, a 12-lead monitoring may be implemented in order to garner a better idea of the issue (Kleber 2019). Other investigations such as echocardiograms and blood tests may need to be considered.

Arrhythmias may cause haemodynamic instability, which can lead to loss of consciousness (UHealth 2018). You should notify any rhythm abnormalities to the medical team and compare the patient with their previous 12-lead ECG (if one has been conducted).

Remember to always perform lead placement at the commencement of your shift as well as before and after repositioning the patient to ensure all electrodes and cables are in the correct position.

Additional Resources


References

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