Three(3),Five(5),Ten(10) Lead ECG Lead /Cable/Electrode Placement
Hi, This is another article to guide the users for ECG lead electrodes/cables placement from team Biometric Cables, a company engaged in manufacturing of ECG Cables for the past 15 years.
In this guide, we will explain the ECG lead/ Cable/Electrode placement in a simplified manner.
Electrocardiograph is an Instrument used to record electrical activity of the heart, non-invasively, which reflects contraction and relaxation of Cardiac muscles in a Cardiac cycle.
Basics of ECG:
An Electrocardiogram or ECG is also known as EKG in German speaking countries
There are of two types of Electrocardiogram used for diagnosis:
Monitoring Electrocardiogram- Real time display of the ECG waveform on a Multi-parameter Monitor. Generally, the ECG waveform is of 3/5/6 leads.
Recording Electrocardiogram- Capture of ECG waveform for a given time and the ECG waveforms printed as Graphical representation in an ECG Machine. Generally, the waveform is of 12 ECG Leads.
ECG waveform Interpretation
Fig (a) ECG Waveform Representation
A normal Cardiac cycle comprises of:
Atrial depolarization represented by P Wave.
Depolarization of Atrial i.e. Intra-Ventricular Spectrum represented by Q Wave.
Depolarization of main mass of ventricles represented by R Wave (i.e. upward Deflection after Q wave).
Repolarization of Ventricles represented by S Wave (i.e. Downward deflection after R wave)
Repolarization of Ventricles represented by T Wave.
Placement and Position of Chest Leads (ECG Leads Position and Placement):
Before placing the ecg electrodes on Human body, we need to understand the logic based on which the electrodes/ ecg leads are placed.
The Heart is located behind and slightly to the left of sternum. The electrical activity arises out of heart muscles and passes through the soft tissues which can be harnessed superficially over the skin. Hence it is important to know the anatomy before placing the electrodes in right place.
Fig. B: Placement of chest leads
Skin is a poor conductor of electricity and therefore skin resistance plays a critical role in acquisition of ECG trace quality.
To reduce resistance at the skin and ecg electrode contact following steps are to be taken
1) If needed excessive hair on the skin must be removed with water, soap and non-alcohol wipes.
2) The skin must be dry and free from dead cells and oil.
3) Dry the Skin vigorously to increase the Capillary blood flow of the tissue.
4) Electrodes must be full contact with the skin.
5) Choose proper position of electrodes based on manufacturer’s recommendation.
A pair of electrodes or a combination of several electrodes through resistance network that gives an equivalent pair is referred as a Lead.
There are 3 type of leads in typical ECG wave forms:
Unipolar /Augmented leads( aVR, aVL,aVF)
Bipolar leads ( Lead I, Lead II, Lead III)
Precordial / Chest Leads ( C1,C2,C3,C4,C5,6)
A lead consisting of Single positive electrode and a reference point is a unipolar lead also called augmented lead
aVR: Right arm absolute potential
aVL: Left arm absolute potential
aVF: Left leg absolute potential
A lead consisting of two electrodes of opposite polarity is called bipolar lead, Bipolar lead wave forms derived from Limb Electrodes.
Lead I - Potential difference between right arm and left arm
Lead II - Potential difference between right arm and left leg
Lead III - Potential difference between left arm and left leg
Chest/ Precordial Leads:
It employs an exploring electrode to record the potential of the heart action on the chest in SIX different positions. They are also Unipolar leads.
These leads are represented by capital letter ‘C’ followed by a subscript numeral which represents the position of the electrodes on the pericardium.
C1- Fourth intercostal space to the right of Sternum
C2- Fourth intercostal space to the left of Sternum
C3- Midway between C2 and C4
C4- Fifth intercostal Space at Mid- clavicular line
C5- Same level as C4 on anterior axillary line
C6- Same level as C4 on Mid- axillary line
Three (3) lead ECG Electrode/Cable Placement:
A 3-lead configuration requires the placement of three electrodes; one electrode adjacent each clavicle bone on the upper chest and a third electrode adjacent the patient's lower left abdomen. It is Typical Bipolar Lead form and Monitor reads as Lead I,II & III
Fig (c) 3 lead ECG Placement
Five (5) lead ECG Electrode/Cable Placement:
A Five(5) lead configuration requires the placement of the three electrodes in the Three (3)-lead configuration with the addition of a fourth electrode adjacent to sternum (right side of Fourth intercostal space) and a fifth electrode on the patient's lower right abdomen. It is Bipolar Lead form and Monitor reads as Lead I,II & III along with Chest lead “C”
Fig : ( d ) 5 Lead ECG Placement
Six (6) lead ECG Electrode/Cable Placement:
The 6 Lead ECG method consists of 6 electrodes including four limb and two chest electrodes. It can help us monitor Bipolar and augmented leads. The Ca and Cb should be placed in two of the positions of C1 to C6,The following combinations may be used C1&C3,C2&C5,C3&C5,C1&C4,C2&C4,C3&C6,C1&C5
Fig (e) 6 Lead ECG Placement
Ten (10) lead ECG Electrode/Cable Placement:
A 12-lead configuration requires the placement of 10 electrodes on the patient's body. Four electrodes, which represent the patient's limbs, include the left arm electrode (L lead), the right arm electrode (R lead), the left leg electrode (F lead), and the right leg electrode (N lead). Six chest electrodes (C1-C6 leads) are placed on the patient's chest at various parts. The recording consists of three Augmented Leads aVR,aVL & aVF, Three Bipolar leads Lead I,II,III and Six unipolar Precordial leads to complete the 12 channel ECG
Fig ( f ) 10 Lead ECG Placement
Summary : The above guide is to educate, inform and help the users, technicians in placing the electrode/cable combination on human subject in a Simplified ideal way. Please feel free to respond back to us with suggestions to firstname.lastname@example.org .
Great information. Easy to understand to present for education.