12 LEAD ECG - CORRECT ECG LEAD PLACEMENT

AHA – AMERICAN HEART ASSOCIATION

This system most often has the ID’s and colors as follows: see Figure 2, (Crawford & Doherty, 2010; Crawford & Doherty, 2009):

• Right Arm Lead: ID – RA, Color White;
• Left Arm Lead: ID -LA, Color Black;
• Right Leg Lead: ID-RL, Color Green;
• Left Leg Lead: ID- LL, Color Red;
• First Chest Lead: ID – V1, Color Red;
• Second Chest Lead: ID-V2, Color Yellow;
• Third Chest Lead: ID-V3, Color Green;
• Forth Chest Lead: ID-V4, Color Blue;
• Fifth Chest Lead: ID-V5, Color Orange;
• Sixth Chest Lead: ID-V6, Color Purple;

IEC – INTERNATIONAL ELECTROTECHNICAL COMMISSION

The leads in this system most often have the ID’s and colors as follows: see Figure 3, (Crawford & Doherty, 2010; Crawford & Doherty, 2009):

• Right Arm Lead: ID - R, Color Red;
• Left Arm Lead: ID - L, Color Yellow;
• Right Leg Lead: ID- N, Color Black;
• Left Leg Lead: ID - F, Color Green;
• First Chest Lead: ID - C1, Color Red;
• Second Chest Lead: ID - C2, Color Yellow;
• Third Chest Lead: ID - C3, Color Green;
• Forth Chest Lead: ID - C4, Color Brown;
• Fifth Chest Lead: ID - C5, Color Black;
• Sixth Chest Lead: ID - C6, Color Purple;

THE MODIFIED ECG LIMB LEADS PLACEMENT

In certain emergency cases, it can be difficult to place the ECG limb leads on the limbs. Because of this dilemma, Takuma, et al. (1995) suggested an alternative ECG limb leads placement technique. This modified ECG leads placement system suggests that the ECG limb leads could be placed on the left and the right Acromial region for the upper limb leads, and on the left and right Anterior Superior Iliac Spine for the inferior limb leads. See Figure 5. The benefit of this modified ECG limb leads placement technique is that it is much faster and easier to be performed when compared to the standard one. It also reduces the muscular artefacts that are recorded with the standard ECG lead placement technique (Takuma, et al., 1995; Jowett, et al., 2005). This modified ECG lead placement system comes at a cost as it interferes badly with the way Einthoven’s Triangle is generated (Toosi & Sochanski, 2008), Figure 6. In other words, if the ECG limb leads are placed on the torso as pictured in Figure 5, the ECG waves that are recorded on the standard 12 lead ECG tracing will have some misleading differences and, therefore, may lead misdiagnosis. (Toosi & Sochanski, 2008; Jowett, et al., 2005).

RECOMMENDATION

To avoid any misdiagnosis, it is recommended to use the standard ECG lead placement system whenever possible, Figure 4 (Campbell , et al., 2017), especially if an Acute Myocardial Infarction is suspected (Toosi & Sochanski, 2008). If it is not possible to use the standard system and a modified ECG lead placement system is used, it is recommended to document this infromation on the 12 lead ECG tracing (Toosi & Sochanski, 2008). Sometimes in clinical practice, the 12 lead ECG tracing is repeated after a specific period of time. Most of the time, this new ECG tracing will be compared with the previous ECG tracing to see if any new changes appear. If one of the 12 Lead ECG tracings is recorded with the standard ECG limb lead placement system, Figure 4, and the second one with the modified ECG limb lead placement system, Figure 5, , differences between the two ECG tracings will occur which are not related to any underlying disease. In some cases these changes might lead to misdiagnosis. Therefore, it is recommended that the ECG tracing is to be labeled every time the modified ECG limb leads system, Figure 5, is used (Kligfield, et al., 2007; Eldrige , et al., 2014).

HOW TO PUT ECG LEADS ON CHEST

WHERE TO PLACE ECG LEADS ON CHEST

The chest leads are placed correctly as follows (Crawford & Doherty, 2010; Eldrige , et al., 2014), Figure 7:

• Chest Lead V1/C1 - Is the first ECG chest lead to be attached, and it has to be placed in the 4th Intercostal Space on the Right Border of the Sternum.
• Chest Lead V2/C2 - Is the second ECG chest lead to be attached, and it has to be placed in the 4th Intercostal Space on the Left Border of the Sternum.
• Chest Lead V4/C4 - Is the third ECG chest lead to be attached, and it has to be placed in the 5th Intercostal Space on the Mid-Clavicular Line.
• Chest Lead V3/C3 - Is the fourth ECG chest lead to be attached, and it has to be placed midway between V2/C2 and V4/C4.
• Chest Lead V5/C5 - Is the fifth ECG chest lead to be attached, and it has to be placed on the Anterior Axillary Line at the same level with V4/C4.
• Chest Lead V6/C6 - Is the sixth ECG chest lead to be attached, and it has to be placed on the Mid-Axillary line at the same level with V5/C5 and V4/C4.

WHAT HAPPENS IF CHEST LEADS ARE MISPLACED ?

Medani, et al. (2018) showed in their study that only in 34% of cases the ECG chest leads were placed correctly. When it comes to the ECG chest leads placement, the most common misplaced leads are: chest lead V1 and chest lead V2, along with chest lead V5 and chest lead V6, (Rajaganeshan, et al., 2007; Medani, et al., 2018). When performing a 12 lead ECG and a proper ECG lead placement technique is not used or ignored for any reason, there is an increased risk of misplacing the ECG leads. By misplacing the ECG chest leads, the 12 lead ECG tracing might be misleading, and in some cases, it might falsely show an Acute Myocardial Infarction (Ilg & Lehmann, 2012; Harrigan, et al., 2012). Therefore, any ECG lead misplacement should be avoided at all costs.

HOW TO PLACE ECG LEADS ON CHEST ?

The easiest way of misplacing the first and second ECG chest leads is by guessing the approximate location of the 4th Intercostal Space. Anyone who is locating the 4th Intercostal Space simply by looking at the skin is greatly contributing to higher chances of a misdiagnosis. To avoid any misplacements of the leads, a standard ECG chest leads placement technique has been developed, which is a technique that uses anatomical landmarks (Crawford & Doherty, 2010). This technique requires a basic knowledge of the thoracic anatomy: the location of the Sternum, the Sternal Jugular Notch, the Sternal Angle of Lewis, the Clavicle and the Intercostal Spaces, see Figure 8 (Crawford & Doherty, 2010). In some patients, the palpation of the Intercostal Spaces can be difficult, but the Jugular Notch of the Sternum is easy to palpate in most patients. The Jugular Notch taken as a landmark along with a specific technique can give us an accurate estimation of where the 4th Intercostal Space is located (Day, et al., 2015). Therefore, if an accurate ECG chest leads placement is wanted, these chest anatomical landmarks should be used (Campbell , et al., 2017; Kligfield, et al., 2007).

CHEST ANATOMY FOR CHEST LEAD PLACEMENT

For a better understanding of where all these landmarks are located, let’s review the basic anatomy of the chest.

The Sternum also known as the breastbone, Figure 9, has a notch at its top, named the Jugular Notch of the Sternum. The Jugular Notch can be palpated easily even in obese patients (Day, et al., 2015). The Jugular Notch can be palpated at the base of the neck Figure 8, and it is felt as a depression.