Cardiac Monitor Set-up and Lead Placement
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Alterations in electrode position may distort the appearance of the waveform significantly, leading to misdiagnosis or mistreatment.
Do not use an EASI-derived 12-lead electrocardiogram (ECG) and its measurements for diagnostic interpretations; they are approximations to a conventional 12-lead ECG.
Continuous cardiac electrophysiologic monitoring is performed routinely for most acute and critically ill patients. A key component of such monitoring is the ECG, which provides a continuous graphic picture of electrical activity generated by the depolarization and repolarization of cardiac tissue. These images may be used for diagnostic, documentation, and treatment purposes. Cardiac electrophysiologic monitoring by hardwire and telemetry is indicated for patients in critical care units, progressive care units, telemetry units, postanesthesia care areas, operating rooms, and emergency departments.
Hardwire ECG monitors have electrodes and lead wires that are attached directly to the patient. Impulses are transmitted directly from the patient to the monitor. Telemetry systems have electrodes and lead wires that are attached from the patient to a battery pack transmitting impulses to the monitor via radio-wave transmission. Telemetry is useful for progressive ambulation and when evaluating a patient's activity tolerance. A disadvantage of telemetry is that ambulation and activity may increase distortion of the ECG pattern, causing artifact.
Specific areas of the chest are used for placement of electrodes to obtain a view of the electrical activity in a particular area of the heart. ECG monitors use a three-lead or five-lead wire system to provide different views of the heart’s electrical activity. The three-lead system is the oldest and simplest of all cardiac-monitoring lead systems. Only one lead is displayed, lead I, II, III, MCL1, or MCL6. This system is used in many portable monitors and defibrillators. The five-lead system is commonly used in most organizations. This system provides views from the six limb leads (I, II, III, aVR, aVL, aVF) plus one precordial (C or V) lead. Six-lead systems are also now available, and these systems allow monitoring of two precordial leads.
Standardized placement of leads is important so the information obtained is assessed in a common frame of reference and appropriate judgments may be made on the patient's cardiac status. The two major factors that determine the views of the ECG deflection on the monitor are the location of the electrodes on the body and the direction of the cardiac impulse in relation to the position of the electrode.
A basic rule of electrocardiography is the rule of electrical flow. This rule notes that if electricity flows toward the positive electrode, an upright pattern is produced on the monitor or graph paper. If the electricity flows away from the positive electrode (i.e., toward the negative electrode), a downward pattern or deflection is produced on the monitor or graph paper.
Lead wires attached to the patient are coded:
Information from the bedside via hardwire or telemetry may be transferred to a central monitor for printing, storage, and analysis. Many central monitoring and bedside monitoring systems provide a continuous readout of two or more leads simultaneously. This readout provides more information and a comparison of the ECG patterns. Optimal lead selection is based on the goals of monitoring for each patient’s situation. The basic goals of ECG monitoring are to monitor patients for rate or rhythm changes, myocardial ischemia and injury (ST monitoring), and to monitor the QT or QTC interval in patients at risk of torsades de pointes.undefined#ref5">5
Using a traditional 12-lead configuration is impractical for continuous monitoring. However, bedside EASI 12-lead monitoring provides all 12 views of the heart on a continuous basis using only five electrodes. The continuous 12-lead ECG may be accessed for information over a predetermined time per the organization’s practice, greatly expanding the information available from bedside monitors. However, an expert consensus has not been achieved for replacing 12-lead ECGs, the gold standard of cardiac monitoring, with EASI-derived ECGs.
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Rationale: When activated, the central monitoring system alarm will sound if problems with the ECG need attention.
Assess the patient to confirm findings, verify ECG patterns, and evaluate computer interpretations.
Rationale: The type of system available determines possible placement of electrodes and the leads that may be viewed.
Rationale: This check reduces the chance of disconnection, distortion, or outside interference with the ECG tracing.
Rationale: The goals of bipolar monitoring using a three-lead system include tracking heart rate, detecting R waves for synchronized cardioversion, and detecting ventricular fibrillation.
Rationale: One limb lead and one precordial lead may be displayed simultaneously with a two-channel system. V1 is the recommended precordial lead. Use leads V1 and V6 for diagnosing arrhythmias with a wide QRS complex (e.g., bundle branch blocks, ventricular pacemaker rhythms, and wide QRS tachycardias).3
EASI-derived 12-lead ECGs and their measurements are approximations to conventional 12-lead ECGs; do not use them for diagnostic interpretations.
Rationale: Placing electrodes on the chest and then attaching the lead wires may be uncomfortable for the patient and may contribute to the development of air bubbles in the electrode gel, which may decrease conduction and distort the ECG image.
Rationale: The sternal notch identifies the second rib and provides a landmark for locating the fourth intercostal space (ICS) for accurate placement of electrodes.
Rationale: Moist skin is not conducive to electrode adherence. Wiping the electrode area with a washcloth or gauze dries and roughens the skin to enhance conduction.2 Some electrodes have a skin abrader on the back that can be used to roughen the surface of the skin.
Do not use alcohol for skin preparation because it dries the skin.2
To obtain good skin contact with the electrodes, clip chest hair with surgical clippers as necessary.
Rationale: Gel may dry out in storage. Gel should be moist to allow impulse transmission.
Use electrodes packaged in large quantities shortly after the package is opened because exposure to air over an extended time dries out electrodes and reduces their adhesive and conductive properties. Tightly reseal the package.
Rationale: Electrodes must be placed tightly to prevent external influences from affecting the ECG. Pressing on the gel pad may cause the gel to leak onto the adhesive surfaces and create air pockets that can interfere with transmission.
Place skin electrodes carefully and consistently to ensure accurate ECG interpretation, which is based on precise placement of skin electrodes on the torso. Incorrect placement of skin electrodes can distort the appearance of the ECG waveform enough that misdiagnosis and therefore inappropriate treatment can occur.
Inaccurate placement of electrodes can affect the morphology (shape) of the QRS complex and result in misinterpretation of a rhythm.1
Rationale: Only one precordial lead may be displayed. Placement of the electrode identifies the lead used.
Rationale: Reducing tension alleviates undue stress on wires and cables that may cause interference or faulty recordings.
Rationale: Creating a stress loop minimizes pulling on the electrodes, which may be uncomfortable for the patient.
Rationale: The transmitter must be secure, so it is not dropped or damaged.
Rationale: The R wave should be approximately twice the height of the other components of the ECG to obtain proper detection by the heart rate counter in the equipment. In many cases, the accuracy of the alarm system depends on the R wave. If the T wave is nearly equal to the R wave, double counting may occur, resulting in false alarms. Manufacturers provide for calibration of the ECG to 1 millivolt, and monitors have size adjustments that may be used to increase or decrease the size of the ECG.
Rationale: This review identifies the normal conduction sequence and abnormalities that may require further evaluation or treatment.
Rationale: Setting alarm limits activates the bedside or telemetry monitor alarm system. Monitoring systems allow for setting and adjusting alarms at the bedside or at the central monitoring system. The types of alarms may include rate (high or low), abnormal rhythms or complexes, and pacemaker recognition, depending on the manufacturer. Establish policies and procedures for managing the alarms.4
Never turn off the monitor alarms.
Rationale: A clear pattern is required to make accurate judgments about the patient's status and treatment.
Reportable conditions: Changes in cardiac ECG complexes, rate, rhythm
Rationale: Changes in the ECG pattern may indicate significant problems and require immediate intervention or additional diagnostic tests (e.g., 12-lead ECG).
Reportable conditions: Changes in cardiac rate and rhythm, hemodynamic instability
Rationale: Skin integrity must be maintained for a clear picture of the ECG.
Rationale: Replacing electrodes every 242 to 48 hours5 prevents drying of the gel and may decrease the number of false and technical alarms.2
Rationale: Electrode resistance changes as the gel dries, so changing all electrodes at once prevents differences in resistance among electrodes.3
Reportable condition: Alteration in skin integrity
Rationale: Accurate interpretation of many arrhythmias depends on proper placement of the electrodes.
Rationale: Changing batteries before they are depleted safeguards against an interruption in ECG monitoring.
*In these skills, a “classic” reference is a widely cited, standard work of established excellence that significantly affects current practice and may also represent the foundational research for practice.
Adapted from Wiegand, D.L. (Ed.). (2017). AACN procedure manual for high acuity, progressive, and critical care (7th ed.). St. Louis: Elsevier.
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