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3-Lead Electrode Placement Chart
Proper skin preparation and electrode placement is essential for clear waveforms. LSI’s 3-Lead Electrode Placement Chart gives 3 easy steps for correct placement.
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. OVERVIEWContinuous 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. EDUCATION
ASSESSMENT AND PREPARATIONAssessment
Preparation
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MONITORING AND CARE
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REFERENCES
*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. AACN Levels of Evidence
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