ECG Information and Lead Placement Instructions

Youth Heart Watch talks about what an electrocardiogram (ECG) is, why they are important tests, and demonstrates how one is performed.


ECG Information and Lead Placement Instructions

Victoria Vetter, MD, FAAP, FACC: Hi, I'm Dr. Victoria Vetter. I'm a pediatric cardiologist -- a children's heart doctor -- and the Medical Director of Youth Heart Watch at the Children's Hospital of Philadelphia, an affiliate of Project Adam. Our mission is to prevent sudden cardiac death in the community through prevention, education, research, and advocacy.

For years at the Children's Hospital of Philadelphia, we have performed electrocardiographic screenings with electrocardiograms -- ECGs -- in local communities as part of our heart health screening study. Many family foundations and some health systems offer ECG screenings to identify children with conditions that may put them at risk for sudden cardiac arrest.

At every screening, children are found with undiagnosed heart conditions, some at risk for sudden cardiac arrest. Once identified, these children can be referred for appropriate diagnostic testing that could include echocardiograms, exercise stress testing, ECG ambulatory monitoring, and genetic testing in selected cases. Then medical or lifestyle interventions can result in improved outcomes and enhanced quality of life.

The objective of this video is to describe the best practices to obtain quality ECGs in children and adolescents. As with any other medical test, it is critically important that the correct policies and procedures be followed to provide the best information from the electrocardiogram.

We provide this video to help standardize these best practices. While ECG machines may differ from one manufacturer to another, and the technical specifications vary, the basics remain and the methods of recording an ECG should not vary significantly from one location to another. The lead placement is critically important and should be precisely applied, as abnormal lead placement can lead to incorrect or missed diagnoses. After learning the background and best practices in the performance of the ECG, you can view scenarios of live participants receiving an ECG from one of our ECG technicians at the Children's Hospital of Philadelphia. The electrocardiogram is often a screening test suggesting the need for additional cardiac testing and evaluation. Recording an electrocardiogram, ECG for the English spelling or EKG for the German spelling, allows us to determine the heart rate and rhythm and where the heartbeat originates.

This is an illustration of a normal ECG showing a normal rhythm called normal sinus rhythm. The ECG can be a diagnostic test for certain abnormal rhythm conditions such as the Wolff-Parkinson-White -- or WPW -- pattern; a prolonged QT interval, as in long QT syndrome; or Brugada pattern, as in Brugada syndrome. The electrocardiogram is a recording of the electrical activity of the heart inscribed over time. The equipment required to perform an ECG includes an ECG machine, ECG lead wires and electrode sensors. Current ECG machines in hospitals include a basic unit comprised of complex electronics, computer elements, amplifiers, computerized algorithms and other components to receive, transmit, and often interpret ECG signals. This is the Cardiac Insight or Cardiac 20/20 ECG system that can be connected to a computer and have various cardiac symptoms captured along with the ECG.

The international ECG criteria are incorporated to help with ECG interpretation. In addition to the basic machinery, each machine is equipped with wires designated to record from a specific electrode sensor or pairs of sensors. The wires placed on the arms and legs are called limb leads. Leads placed on the chest are called chest or precordial leads.

An electrode sensor is a conductive pad comprised of an adhesive patch attached to the skin, allowing electrical activity from the heart to be transmitted via wires to the ECG machine, recorded on the ECG paper and stored electronically for measurements and interpretation.

The ECG settings that are important include paper speed, filters and calibration. Before recording, you will need to provide unique information for each subject. You will need to input the name and identifying information for the subject, including date of birth, medical or study IDs into the ECG machine. To further prepare for the performance of the ECG, the table, machine and lead wire should be cleaned before each use.

All needed materials should be prepared to be used for the next participant after each use. The table should be covered with examination table paper, changed for each participant. Skin preparation and electrode connections are important. Proper skin prep helps ensure ECG tracing quality.

If the participant's skin is sweaty, dirty, or oily, you should clean with alcohol and allow the skin to dry before placing the electrodes. If the lead and electrode sensor connection is a snap, especially in young children, it is good to clip the leads to the electrode sensors first, to avoid pushing on the child's chest.

If the connection is a clip, the electrode sensors can be placed first and the clips attached. A private setting should be provided for both males and females, preferably behind curtains or screens and on a comfortable examining or massage table. Males are asked to remove their shirts. Areas with significant hairiness should be shaved with a safety razor to ensure a good connection between the electrode and skin.

Girls should be provided with a gown or cover. The gowns are available for female. The bra can be removed. If not, it can be loosened by the connectors or pulled up slightly if it is a sports bra. Leads can then be put in the correct interspace positions and the bra pulled back down. If the correct position is under the breast tissue, the breast can be slightly lifted and the patient can help with the lifting while the lead is placed in the correct position on the chest. You should always provide instructions for screenings to participants prior to the ECG performance. The participants should be directed to wear comfortable, non-constrictive clothes or be given a gown. Sheets or small blankets should be available for privacy and comfort.

Participants should try to come before a sports practice or game, to be well hydrated, but should not drink cold beverages just before the ECG. If they are having fast heart rates, they can be given something to drink and allowed to rest for 15 to 20 minutes prior to the ECG performance. They should not be sweaty or wet. A towel should be available to dry the skin as needed.

These are the steps that we suggest for the procedure, which can be modified for your setting.

Jennifer: Hi, I'm Jennifer. I'm going to be doing your ECG today.

Victoria Vetter, MD, FAAP, FACC: The participant should be made to feel comfortable. Procedure should be explained while the person is still seated in a chair or on the table and asked if they have any questions before proceeding. All questions should be answered and assurance provided. The participant should understand that the ECG is a non-invasive procedure that should take 10 minutes or less.

Ask a participant to lie flat on their back. If they are uncomfortable lying flat, a small towel can be rolled up and placed under the head or neck as a pillow or neck support. Make sure your participant is relaxed or artifact will cause extra signals and affect the appearance of your ECG.

With regard to electrode and lead placement for the limb leads, there are four wires that connect to electrodes on each of the limbs.

Right arm, abbreviated RA; left arm, LA; right leg, RL; and left leg, LL. For the chest leads, there are six wires that connect to the chest and are called chest or precordial leads for the standard 12-lead ECG and nine for the 15-lead ECG. Thus 10 wires result in the 12-leads or views for the 12-lead ECG.

The different leads allow interpretation of different areas of the heart. If a lead becomes loose at any time, it will need to be replaced. Some ECG machines will tell you which lead is loose. Lead placement is the most important element to obtaining an accurate and useful ECG. Lead placement is so important because moving the electrode only a few millimeters makes a major difference in the signal that is recorded and can cause false positive and false negative recordings.

Placing the leads below the bra line in a woman makes the ECG worthless, as that position will always be too low. Chest lead placement can be done correctly on a female and in a respectful manner. Placing the leads on hair in a male will prevent good contact and the signal will not be correctly transmitted. Correct limb lead placement involves placing limb leads on distal arms and legs near the wrist and ankles and not on the torso or chest. Be careful not to reverse arm or leg leads, which is called limb lead reversal. Always check lead labeling on the leads to prevent reversal. Different lead positions take a picture of the heart from different views.

The position of the precordial or chest electrodes is determined by the surface of the chest. It is predicated on the assumption that the relationship of the heart is similar in each person, but with multiple different body shapes, that may not be the case. However, it is the closest we can get to having a standard lead placement.

Our demonstrations on actual patients of different ages and genders will help you with this challenge. This illustration shows the position of the heart in relation to the skeleton. The apex of the heart normally points to the left side. The operator should know how to position the leads on the chest.

To do this, you will need to know where the leads go relative to standard positions or landmarks on the chest. The first landmark is a breast bone in the center of the chest. It is called the sternum. The top of the breast bone is called the manubrium. About two to three finger breadths down, it connects to the main part of the breast bone.

This area is referred to as a sternal angle and can be felt as a protuberance connecting the top and lower portions of the breast bone. This is important because it is across from the second rib. You can also identify the rib number by counting down from the collarbone or clavicle. The rib just below the collarbone is the first rib.

You can count down from the first ribs, to fourth and fifth ribs along the subject's left side of the breast bone. Feel down along the breast bone on the subject's left side until you reach the fourth rib. The space below the fourth rib is called the fourth intercostal space and is the most important landmark for you to find.

You should practice finding this landmark on another person until you feel comfortable. You can then move down one more rib to the fifth rib and find the space between the fourth and fifth ribs. Also, note the middle of the collarbone in your mind's eye, draw a line toward the feet. This is called the mid-clavicular line.

With the arm raised up, you should also draw an imaginary line from the front, middle, and back of the armpit called the anterior, mid, and posterior axillary lines. Chest lead placement in relation to the ribs is shown in the illustration. Note, the right and left side of your subject. The intercostal spaces are the spaces between the ribs.

This means the fourth intercostal space is between the fourth and fifth ribs. The fifth intercostal space is between the fifth and sixth ribs. V1 is placed in the fourth intercostal space along the patient's right side of the breast bone between the fourth and fifth ribs, as shown in the picture. V2 is placed in the fourth intercostal space along the subject's left side of the breast bone between the fourth and fifth ribs. V4 is placed in the fifth intercostal space along the patient's left side of the breast bone in the space between the fifth and sixth ribs in a line down from the middle of the collarbone, the mid-clavicular line. V3 is placed midway between V2 and V4.

V5 is placed in the fifth intercostal space along the subject's left side of the breast bone, in the space between the fifth and sixth ribs, the same space as V4 in the line down from the front of the armpit when the arm is held up -- the anterior axillary line. V6 is placed in the fifth intercostal space, in the space between the fifth and sixth ribs -- same space as V4 and V5 in the line down from the middle of the armpit when the arm is held up, the mid-axillary line. V7 is also placed in the fifth intercostal space, in the space between the fifth and sixth ribs, the same as V4, V5 and V6, and the line down from the back of the armpit when the arm is held up, the posterior axiliary line. V3R is placed directly across from V3, but on the subject's right side, as shown in the picture.

V4R is placed in the fifth right intercostal space in the space between the fifth and sixth ribs, in a line down from the middle of the collarbone on the subject's right side, the mid-clavicular line.

First, I'm gonna feel your collarbone. The space right below that is where the first rib is. There's a space under the first rib.

Then I'm feeling the second rib. Then I'm feeling your third rib, and then I'm feeling your fourth rib and the space in between your fourth and your fifth rib, I'm gonna put lead V2. Right on the opposite side, on your right side, in that same space between the fourth and the fifth ribs, I'm gonna put lead V1.

Then in that imaginary line, in the middle of your collarbone and one space down between the fifth and the sixth rib, I'm gonna put lead V4, and then I'm gonna put lead V3 right in the middle of it. Then I'm gonna go straight across and I'm gonna put -- raise your arm up so I'm sure I'm in the right place.

There's an imaginary line in the front of your armpit, and I'm gonna call that V5, and then right in the middle of your armpit is V6, and then right in the back of your armpit is V7.

After placing the leads, proceed with recording the ECG. Push the button, when there is no artifact or motion across the whole screen. It can be pushed again if not correct. Be sure the ECG is saved that is required for your system. You have now completed the ECG recording. Disconnect carefully to avoid pulling on the adhesive.

Provide a towel, paper towel or alcohol as needed to clean up the area where the electrodes were placed. Allow privacy to redress. Thank the participant and ask if they have any questions. Do not provide any interpretation of the ECG, even if the machine reads ECG, as it may not be correct. Thank you for your attention to this presentation.

Related Centers and Programs: Youth Heart Watch