EKG: Cardiac Monitoring and 12-Lead EKG Basics

Contents

Cardiac Monitoring and 12-Lead EKG Basics: Overview

Focus topic: Cardiac Monitoring and 12-Lead EKG Basics

The electrocardiogram (EKG) measures the heart’s electrical activity by showing the exact progression of electrical events during depolarization and repolarization. The EKG allows health care professionals to monitor the work of the heart as demonstrated by the unique waveforms it produces. These waveforms demonstrate the phases of contraction and aids in the identification of rhythm disturbances. Health care professionals can also use this to assess for disease and injury related to heart function, to evaluate pacemaker performance, to determine the effects of medications and electrolytes, and as a baseline of normal patient assessment for future reference. To do this, electrodes are placed at specific locations on the patient’s skin to sense the electrical current and transmit them to an EKG monitor.

Clinical Alert

The EKG is not able to demonstrate the contractile strength of the heart. Other modes of testing, such as an echocardiogram, are available to help with this piece of assessment. Both blood pressure and pulse can provide important evidence of performance of the cardiac system.

Cardiac Monitoring and 12-Lead EKG Basics: Types of Electrocardiograms

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There are two types of EKGs: the rhythm strip and the 12-lead. Types of EKGs describes these EKGs.

Cardiac Monitoring and 12-Lead EKG Basics: Types of EKGs

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Cardiac Monitoring and 12-Lead EKG Basics: Monitoring Systems

Focus topic: Cardiac Monitoring and 12-Lead EKG Basics

The two EKG monitoring system types are hardwire and telemetry.

Cardiac Monitoring and 12-Lead EKG Basics: Hardwire

Focus topic: Cardiac Monitoring and 12-Lead EKG Basics

Hardwire monitoring is most commonly used in emergency departments, intensive care units, postanesthesia care units, or surgical suites. This type allows for continuous observation. These can also be electronically transmitted to a main console so that more than one patient can be observed at a time. In this type of monitoring, the electrodes are connected directly to the cardiac monitor that is permanently secured to the wall near the patient’s bed or they could be mounted on a device similar to an IV pole so that they can be moved between patients and/or rooms. Each monitor is different and may have a variety of attachments or monitoring capabilities depending on the company. Parameters such as blood pressure, pulse oximetry, capnography, and other hemodynamic measurements can be a part of the functionality of the hardwire bedside monitor as well as being able to capture rhythm abnormalities and monitor for injury patterns that may be evolving for the patient. EKG tracings or rhythm strips can be transmitted to the main console so that print copies may be maintained of the patient’s cardiac activity. The disadvantages of hardwire monitoring are: patient discomfort due to restricted movement by the monitor cable and electrodes, the disconnection of leads or the presence of extraneous waveforms that may present on the screen as life-threatening dysrhythmias as the patient moves about in the bed, patient discomfort due to electrode placement and removal, especially for men with hair on their chests, the presence of diaphoresis (sweating) on the patient in which electrode attachment becomes difficult, and a feeling of being “tied down” by the patient.

Cardiac Monitoring and 12-Lead EKG Basics: Telemetry

Focus topic: Cardiac Monitoring and 12-Lead EKG Basics

Telemetry is used for more mobile patients in medical-surgical and step-down units. This system monitors only heart rate and rhythm and can be used for detecting dysrhythmias. Telemetry uses electrodes placed on the patient’s chest with the electrodes then connected to a small battery-powered transmitter box. The patient can carry this transmitter box in a pocket or a pouch with a strap that can be worn across the shoulder or around the neck. The transmitter sends electrical signals to a monitor screen at a different location where the tracings can be printed and analyzed. One screen can monitor multiple patients. Electrodes are still utilized with this style of monitoring and the same problems can occur as above such as disconnection or the creation of extra waveforms with movement, however, it allows the patient a greater range of mobility and is especially useful in the detection of problems when the patient engages in activities of daily living.

Cardiac Monitoring and 12-Lead EKG Basics: The Process

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Cardiac Monitoring and 12-Lead EKG Basics: Electrodes

Focus topic: Cardiac Monitoring and 12-Lead EKG Basics

Electrodes can be made from paper, plastic, or metal (or any combination of the three) and contain conductive material that allows recording of the heart’s electrical currents. The types of electrodes that are placed on the skin are the metal disk, metal suction cup, and the disposable disk. The disposable disk is the most common type to be used for continuous monitoring purposes. The metal disks and suction cups are more frequently used for 12-lead EKG purposes (Types of electrodes).

Cardiac Monitoring and 12-Lead EKG Basics: Lead Wire Systems

Focus topic: Cardiac Monitoring and 12-Lead EKG Basics

Lead wire systems utilize either three or five electrodes. These are also known as three-lead and five-lead systems. In the three-electrode system, there is one positive electrode, one negative electrode, and a ground electrode that prevents accidental shock to the patient. This type of monitoring allows visualization of lead I, lead II, or lead III through either the lead selector button on the monitor or by changing the location of the positive, negative, and ground leads. The most common is lead II. The right arm, left arm, and left leg are the electrode positions in the three-electrode system (Placement of electrodes for three-lead system). Telemetry monitoring usually employs this three-electrode system.

Cardiac Monitoring and 12-Lead EKG Basics: Types of electrodes

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Clinical Alert

When placing electrodes for monitoring purposes, the lower limb leads are usually placed on the abdomen, however, they can be placed on the limbs themselves if necessary to obtain a good waveform. Consider the comfort of the patient when determining this. Long wires to the legs can cause problems with positioning in the bed. If a patient has extreme hair on his chest, the right and left arm leads can be placed on the shoulder area or upper arm.

Cardiac Monitoring and 12-Lead EKG Basics: Placement of electrodes for three-lead system

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The five-electrode system is a popular choice due to the ability to monitor any of the 12 leads through the lead selector button on the monitor. For this lead system option, the leads are placed in similar fashion as the three-lead system with the addition of a right leg (RL) lead and a chest lead. The chest lead is moved to the proper position on the chest for each choice of lead monitoring and the proper selection is made on the lead selector. The electrode positions are right arm, left arm, right leg, left leg, and chest (Placement of electrodes for five-lead system). Lead selectors on the monitor allow the health care professional to choose which lead they would like to monitor.

Cardiac Monitoring and 12-Lead EKG Basics: Placement of electrodes for five-lead system

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Clinical Alert

Electrodes are normally universally color coded. Be sure to check in each institution for this color coding, however, the most common is to have red, green, white, black, and brown electrodes. An easy way to remember proper placement is with a mnemonic: “White to the right, red to the bed.” This helps to remember that the white electrode is placed on the right side. The black electrode (the opposite of white) is then placed on the opposite side. With the three-electrode system, the red is then placed “to the bed” or on the left abdomen which is closer to the bed. The five-electrode system is the same except the brown electrode usually goes on the mid chest area and the green electrode goes on the left side of the abdomen, therefore, the colors usually associated with Christmas, red and green, are together on the lower abdomen.

Another form of the five-electrode system is known as the EASI system, also known as a reduced lead continuous 12-lead EKG. In this system, electrodes are placed in a particular fashion on the chest and all 12-leads can be monitored simultaneously. The monitor conducts special mathematical calculations to provide a three dimensional view and a total of 12 views as in a 12-lead EKG. The EASI system correlates well with the 12-lead EKG, but, should not be used in place of the conventional 12-lead EKG. Electrode placement is depicted in Placement of EASI electrodes.

Cardiac Monitoring and 12-Lead EKG Basics: Placement of EASI electrodes

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Cardiac Monitoring and 12-Lead EKG Basics: Application of Electrodes

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Prior to placing electrodes on a patient for either an EKG or cardiac monitor, be sure to provide privacy and explain the purpose of the monitoring or electrocardiogram. Some patients may have misinformation about the procedure and may express fear or concern, such as being “shocked” or that the machine can control their heart rhythm. Allay those fears with simple explanations that the procedure is used to watch the heart activity and that there is no pain involved. If the patient is being attached to a cardiac monitor, discuss that the monitor is very sensitive and that alarms occasionally occur from the machine itself. Clarify that if the patient moves about in the bed or if a lead wire becomes disconnected from the electrode, the monitor will alarm in the same manner as if a dysrhythmia were detected. Also, other parameters can cause the monitor to alarm such as abnormal blood pressures or faulty respiratory readings. Make sure that the patient is aware that even though the health care professional is not in the room, the patient is on a main monitor screen and that they are being viewed at all times. Always answer questions about the monitor for both the patient and significant others prior to leaving the room and secure the call light in an easy to reach location.

Check all equipment to ensure that the EKG machine or monitor and all cables and lead wires are intact (no breakage or fraying) and functioning. Make sure that the appropriate paper is loaded into the machine and is filled. Next, gather the electrode supplies and ensure the electrode gel in the electrodes is moist and has not dried. This conductive gel is necessary to help to bridge across the dead or dried cells that lie on the surface of the skin. If the gel is dry, electrical contact will be decreased and artifacts—waveforms not produced by the heart’s electrical activity—can appear. Attach the lead wires to each electrode. It is usually best to apply the lead wires to the electrodes before placing on the patient to reduce patient discomfort. Snap on electrodes must be pushed on to the end of the lead wire and if the electrode is on the patient, this can cause pain as pressure is applied to make this connection. This can also force the conductive gel out of the electrode and cause problems with making good contact. If the system uses clip-on lead wires, they can be attached after the electrodes are attached to the skin. Another type of lead wire is the pinch variation. These are usually used with the EKG machine to attach to the metal disk type of electrodes. These can be used for monitoring but are more often used for EKG tracings. Choose the appropriate lead placement and expose the patient’s chest. Make sure the patient’s limbs are resting on a supportive structure to reduce muscle tension and tremors which can interfere with proper readings.

Clinical Alert

When exposing the chest, again be aware of privacy and obtain permission from the patient for family members in the room to be present. Do not assume that individuals in the room are spouses or appropriate family members for this type of exposure.

Prepare the patient’s skin by rubbing with a gauze pad, a dry washcloth, or the small abrasive area supplied by the manufacturer on the back of the electrode if necessary. Rub each site until it reddens slightly. Soap and water can be used to cleanse prior to application of the electrode. Alcohol is not recommended for this process as it can dry the skin area. Tincture of benzoin and antiperspirant are also not recommended. However, benzoin might be necessary if the patient is very diaphoretic. This can help the pad stay on the skin. If this is used, be sure to apply a thin layer only to the area that is making contact with the sticky portion of the electrode and not the center where the conductive gel is present. Benzoin can reduce the conduction of the electrical impulses. Allow the tincture of benzoin to dry before applying the electrode.

If excess hair is present, clip this with clippers or scissors. Some commercially available single use clippers are available for this. Shaving is controversial. Check with the institution to determine if shaving is acceptable in that location.

Remove the backing from the electrode and apply to the site by pressing one side of the electrode against the patient’s skin, pulling gently, and then pressing the opposite side of the electrode against the skin. To stabilize the electrode, take two fingers and press the outside of the electrode to ensure it sticks to the patient’s chest. Do not apply electrodes over broken skin, joints, scar tissue, burns, rashes, pacemakers, medication patches, other implanted devices, jewelry, bony prominences, skin folds or creases, or thick muscles. Double check lead wires for secure attachment to the electrodes (Types of lead wires).

Cardiac Monitoring and 12-Lead EKG Basics: Cardiac Monitors and the EKG Machine

Focus topic: Cardiac Monitoring and 12-Lead EKG Basics

Prior to adhering the electrodes and leads to the patient ensure that the EKG machine or cardiac monitor and all involved parts are in sound working order. The electrodes and lead wires for the cardiac monitor are usually all placed on the chest, although the shoulders and upper arms can be used as well. The lower abdomen is used for the lower extremity electrodes. After placing the electrodes and leads and attaching the necessary cables, turn on the cardiac monitor. The EKG waveform should appear.

Cardiac Monitoring and 12-Lead EKG Basics: Types of lead wires

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Once the patient is attached to the monitor, select the appropriate lead and make sure that the rhythm is readable. Either touching the screen, pressing buttons, or turning knobs will make needed adjustments. To select different leads on the cardiac monitor in order to obtain varied views of the patient’s cardiac rhythm, enable the lead selector button. Reset the amplitude if necessary on the machine so that the QRS complexes are captured for correct reading of heart rate. Adjust the size of the waveform by manipulating the gain control and position button.

Reset alarm rates if necessary. Do not turn off alarms. This is a necessary part of monitoring the patient. Set the monitor’s heart rate alarms to 10 to 20 beats per minute higher and lower than the patient’s heart rate. Be sure to consult your facility’s policy for setting these alarms. Consider your patient’s condition and age in case the alarms need to be set to different parameters. The pediatric patient’s heart rate will be normally higher and therefore the alarms may need to be adjusted for this patient. To make sure the monitor is working properly, take the patient’s apical pulse and compare the heart rate you obtain to that which is displayed on the monitor.

Clinical Alert

If a patient is having extra heartbeats such as with premature ventricular contractions, these beats may be counted on the machine, but are not perfusing the patient. By counting the patient’s radial pulse, the health care professional can determine which beats are actually carrying oxygenated blood throughout the body.

If necessary make a printed copy for the chart. The record button on the monitor will print the paper record of the patient’s cardiac rhythm. The paper strip is either printed from the monitor or from a central console. Be sure to label the rhythm strip with the patient’s name, identification number, date of birth, physician’s name, date, time, medications administered, presence of chest pain, patient’s activity during recording, and interpretation of the rhythm.

Again, check on institution policy regarding information necessary on printouts. Some machines may require you to program some of the basic information into the system (such as patient name, date of birth, and date) beforehand so that the information will be automatically printed on the rhythm strip.

Clinical Alert

If situations arise that require interventions for your patient that are related to the readings on the monitor, such as dysrhythmias or heart rates, be sure that the times on the recording are concurrent with the times that are documented in the patient record related to medications given or other treatment regimens that were instituted in response to those problems.

When the multichannel 12-lead EKG machine is used, proper patient identification will need to be entered before the EKG is recorded. (Some cardiac monitors are able to create a 12-lead EKG with the assistance of a special cord that allows the 10 leads to be attached to the patient.) Place the proper electrodes on each limb and across the chest. These are then attached to the lead wires which are marked for the health care professional’s convenience. Make sure that the rhythm on the screen on this instrument is clear and legible before pressing the print button.

Have the patient lie still and refrain from talking. Encourage them to relax with their head resting comfortably on a pillow. Increased respiratory rates and effort will affect the outcome of the reading. Heavy and erratic baselines, as well as loss of a lead on the screen, need to be resolved before printing. If the patient is in an area such as the emergency department and is being observed for the potential of a heart attack, it is usually best to leave the leads in place on the patient’s chest.

If a second EKG is requested at a later time, the lead placements will be exactly the same and proper identification of changes between the two can be detected. Make sure that all appropriate identifying information is on the EKG tracing. Ensure that the provider caring for the patient views the EKG. A 12-lead EKG will have all 12 leads on it and most will also provide a lead II rhythm strip at the bottom of the page. Each lead is labeled and it is easy to see the change to a new lead on the page since each lead has particular identifying characteristics.

Cardiac Monitoring and 12-Lead EKG Basics: Problems with Waveforms and Machines

Focus topic: Cardiac Monitoring and 12-Lead EKG Basics

Some problems that can occur with either the cardiac monitor or the EKG machine are listed below.

  • Malfunctioning equipment: Equipment that is excessively worn or that has broken lead wires and cables can cause incorrect grounding. This can cause an inadvertent electrical shock to the patient.
  • Lack of waveform: The lack of a waveform can be caused by improper electrode placement, a disconnected electrode, dry electrode gel, or failure of a wire or cable. Rectify these situations by repositioning the electrodes, reapplying disconnected electrodes, and replacing dry electrodes or damaged wires or cables.
  • Waveform abnormalities: Waveform abnormalities can occur when the electrodes are not connected to the correct electrode wire, therefore changing the normal positive and negative deflections that create the complexes. If the monitor picture or the EKG tracing does not look appropriate, check for the correct placement of the wires and electrodes.
  • Baseline issues: Several different baseline issues can occur. A wandering baseline causes a baseline that appears jagged or irregular and isn’t stationary (Wandering baseline). Patient movement that might occur due to chilling associated with fever or ambient room temperature, nerves, uncontrolled muscle tremors, seizures, disease processes such as Parkinson’s disease or extra chest wall movement during labored respirations, electrode placement over bone instead of soft tissue, or poor contact between the electrode and the skin can cause a wandering baseline. Rectify these issues by helping the patient relax and remain still, applying warm blankets, treating high fevers, repeating the EKG after treatment for distressed breathing has been accomplished, and by repositioning the electrode. A fuzzy baseline is caused by electrical interference from other equipment in the room, such as razors, hair dryers, or radios. This may be seen as a wide, thickened baseline that also has thin, rapid spikings. This is also known as 60-cycle interference (60-cycle interference). Electrode malfunction and improper grounding of the patient’s bed may also be causes. Resolve a fuzzy baseline by ensuring all electrical equipment is attached to a common ground and the patient’s bed ground is attached to the room’s common ground. Replacing the electrodes and ensuring that three-pronged plugs are not loose may also help. Remove other equipment in the room that may be interfering.
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Cardiac Monitoring and 12-Lead EKG Basics: Wandering baseline

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  • Artifact: Artifact can be manifested in a rough, uneven, wavy type of baseline or in what might appear as extra beats or exaggerated complexes that are not cardiac in origin (Artifact). Excessive patient movement, as seen in seizures, anxiety, and chills, can cause artifact. Other causes of artifact are static electricity; interference from other electrical equipment; malfunctioning, dirty, or corroded lead wires or cables; hair on the chest; and improper electrode placement. In the case of the patient who experiences seizures, notify the practitioner and provide for patient safety by removing surrounding equipment and ensuring the patient doesn’t fall off the examination table or out of the bed. If the patient is chilled or anxious, provide blankets for warmth and therapeutic communication for relaxation or
    treat fevers that are present. Replace malfunctioning, dirty, or corroded lead wires and cables. Reposition or replace the electrodes as required. Ensure all electrical equipment is attached to a common ground and check the three-pronged plug for proper functioning. To combat static electricity, humidify the room to 40%. Artifact can also occur with telemetry when the signals are not being received well. Changing the battery may help with this problem. The patient may also have wandered past the established perimeters for the base station.

Cardiac Monitoring and 12-Lead EKG Basics: 60-cycle interference

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Cardiac Monitoring and 12-Lead EKG Basics: Artifact

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  • False alarms: Both high and low false alarms can register for many reasons. This may be due to artifact that is captured on the screen as high voltage, such as with seizures, patient movement, or having the gain or amplitude too high. Lower the gain control when this occurs. Hyperkalemia can be a cause of a false high rate alarm due to the associated high peaked T waves which are then read along with the QRS complex as another heartbeat. False low rate alarms can occur due to non-contact between the electrode and the skin, dried electrode gel, disconnections between the lead wire and the electrode or the monitor. Low amplitude complexes can also be the cause and in this case, the gain needs to be increased.
  • Weak signal: Faulty or non-functioning wires or cables and improperly applied electrodes can cause a weak signal. Reapply or reposition the electrodes and replace defective equipment. The patient may need to be placed on a different lead. The amplitude or gain on the monitor can also be changed when QRS complexes are very small. When this involves telemetry, checking on the patient location or switching batteries may be helpful.

Clinical Alert

When the monitor registers a rhythm that appears to be a dysrhythmia, be sure to conduct a thorough assessment of the patient to ensure that the abnormal rhythm is actually occurring. Simple patient movements such as sneezing, yawning, laughing, changing positions, or brushing their teeth can be depicted as a life-threatening cardiac event, such as ventricular tachycardia. If an electrode has become unattached, the rhythm on the monitor may resemble a straight line or asystole (no heartbeat). Always treat the patient, not the machine!

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