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Electrocardiographic monitoring in the medical-surgical setting: clinical implications, basis, lead configurations, and nursing implications.

When in-hospital electrocadiographic (ECG) monitoring first was introduced in 1963, the primary purpose was detection of lethal arrhythmias (ventricular tachycardia, ventricular fibrillation) for use in the coronary care unit (CCU) (Day, 1963). Today, ECG monitors can be equipped with sophisticated software for monitoring complex arrhythmias, tracking ECG waveform changes (QT interval), and monitoring the ST segment for myocardial ischemia. Additionally, in-hospital ECG monitoring has expanded well beyond the CCU to include telemetry units, the operating room, invasive and noninvasive laboratory settings, labor and delivery, and medical-surgical units.

Because medical-surgical nurses now commonly encounter ECG monitoring, they must possess a basic understanding of electrocardiography. The basis for ECG monitoring (12-lead ECG), ECG leads and available lead configurations for in-hospital monitoring, clinical implications of ECG monitoring in medical-surgical units, and nursing considerations when implementing ECG monitoring in the medical-surgical environment will be discussed.

Clinical Implications of ECG Monitoring

Current ECG monitors have software capabilities to monitor not only heart rate, but also complex arrhythmias, myocardial ischemia (ST segment monitoring), and ECG waveform interval changes. The goals of ECG monitoring can vary considerably based upon the patient population; however, not all hospital units will need every software feature offered. For example, in settings such as the CCU and cardiac telemetry unit, a high percentage of the patients have, or are being assessed for, acute coronary syndrome; therefore the goals of ECG monitoring include identifying both arrhythmias and acute myocardial ischemia. Staff nurses working in these units must possess the knowledge and skills to perform these specific ECG assessments. In the medical-surgical setting, the goals of monitoring may include simply tracking heart rate and detecting lethal arrhythmias. Nursing leaders, physicians, and staff nurses must reach consensus about the goals of ECG monitoring specific to a unit. This key decision will help determine expected staff proficiencies, facilitate policy and procedure development, guide educational efforts, and determine quality assurance measures related to ECG monitoring. "Practice Standards for Electrocardiographic Monitoring in Hospital Settings" (Drew et al., 2005) is an evidence-based document that may be used as a guide when developing ECG monitoring policies and procedures for medical-surgical units.

Basis of Electrocardiographic Monitoring

The standard 12-lead ECG is considered the noninvasive gold standard for diagnosis of normal cardiac rhythm, dysrhythmias, and myocardial ischemia (Drew et al., 2004; Fisch, 1997; Zipes, 1997). It also can be used to identify chamber enlargement, ventricular hypertrophy, prior myocardial infarction, and drug effects (Macfarlane & Veitch, 1989). An electrocardiograph records and prints a 12-lead electrocardiogram, which is a graphic representation of the electrical activity of the heart from 12 different viewpoints.

An ECG waveform represents one cardiac cycle and includes P, Q, R, S, and T waves (see Figure 1). It is common to measure the following waveform intervals: (a) PR interval (atrial depolarization) = beginning of the P wave to the beginning of the Q wave, (b) QRS interval (ventricular depolarization) = beginning of the Q wave to the end of the S wave, and (c) QT interval (ventricular depolarization and repolarization) = beginning of the Q wave to the end of the T wave.

The standard 12-lead ECG is the basis of electrocardiography. While medical-surgical nurses may not use the standard 12-lead configuration for ECG monitoring, a basic understanding of the system must be appreciated because in-hospital cardiac monitors use a modification of this lead configuration.

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To obtain a standard 12-lead ECG, skin electrodes are placed on each of the four extremities (right and left wrist, right and left ankle) as limb leads (Einthoven, 1902). Six additional electrodes are placed at specific locations on the torso overlying the heart as the precordial leads (Wilson, Johnson, & Rosenbaum, 1944; Wilson, Macloed, & Barker, 1931). An explanation of how the 10 electrodes become 12 leads follows.

While the standard 12-lead ECG is the noninvasive gold standard for assessing cardiac rhythm, dysrhythmias, and ischemia, placement of the four limb leads is impractical for continuous ECG monitoring because they are uncomfortable for patients and cumbersome when mobilizing patients, and they cause muscle artifact that leads to false positive alarms (Drew et al., 2004). Because of this, the limb electrode configuration for continuous in-hospital monitoring was modified to that suggested by Mason and Likar (1966). In this modified 12-lead configuration, the right and left arm electrodes are relocated from the wrists to the infraclavicular fossa close to the corresponding shoulder, and the right and left leg electrodes are relocated from the ankles to the lower abdomen below the umbilicus. Because the right leg electrode serves as the ground or reference electrode, it can be placed anywhere; however, it typically is placed on the right lower abdomen below the umbilicus to make it consistent with the left leg electrode. The six precordial electrodes are placed in the same position for both the standard and Mason-Likar lead configuration.

Figure 2 illustrates electrode placement comparing the standard to the modified, or the Mason-Likar lead configuration. The Mason-Likar 12-lead ECG is recommended for continuous ECG monitoring because it allows multiple leads to be assessed, a situation ideal for distinguishing arrhythmias and detecting myocardial ischemia (Drew et al., 2004). However, it is not uncommon for medical-surgical nurses to have fewer than 12 leads available in the ECG monitoring system on their unit.

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What Is an ECG Lead?

An ECG lead records the difference in electrical potential between a negative and positive electrode placed at specific locations on the body surface (Einthoven, 1902; Graetunger, Packard, & Graybiel, 1951). The standard 12-lead ECG is composed of six limb leads (designated as I, II, III, aVR, aVL, and aVF) which are generated from placing an electrode on each of the four limbs (Fisch, 1997). The remaining six leads (designated as leads V1, V2, V3, V4, V5, and V6) are the chest or precordial leads (Wilson et al., 1944). The limb leads view the frontal plane of the body, while the precordial leads view the transverse or horizontal plane of the body. An ECG lead is either bipolar or unipolar, as will be described in the subsequent section.

The first three leads were introduced in 1902 by Willem Einthoven. Leads I, II, and III are termed bipolar leads because they measure the difference between two leads, with one lead designated as negative and one designated as positive (Einthoven, 1902). The electrical forces generated between the two leads are recorded from the negative to the positive lead. For lead I, the right arm (RA) electrode serves as the negative electrode and the left arm (LA) electrode serves as the positive electrode. For lead II, the RA electrode serves as the negative electrode and the left leg (LL) electrode serves as the positive electrode. For lead III, the LA electrode serves as the negative electrode and the LL electrode serves as the positive electrode. Because the electrical forces of the heart are normally directed inferiorly (downward) and leftward, the ECG waveforms in these three leads predominantly are upright, or positive. Figure 3 illustrates the location of the three bipolar limb leads, which form the Einthoven triangle, and the normal ECG waveforms generated in these three leads.

The second type of lead is called the unipolar lead (Wilson, Johnson, Macloed, & Barker, 1934). Unipolar leads are designated by an upper case V on the ECG monitor and/or printout. One type of unipolar lead, termed the unipolar limb lead, is generated by using the same three limb electrodes (RA, LA, LL) used to generate leads I, II, and III. The unipolar limb leads are designated as aVR, aVL, and aVE Unlike a bipolar lead that measures the difference between two leads (one negative and one positive), a unipolar lead records the electrical potential at a single exploring electrode minus a central terminal created by averaging the electrical potential of the other two limb leads. The central terminal used to create the unipolar limb leads is created electronically in the ECG machine. The designation of the unipolar limb leads (aVR, aVL, and aVF) requires some further explanation. Goldberger (1942) modified Wilson's central terminal in order to increase the recorded voltages. The resultant lead was augmented or amplified by 50%. The lower case letter "a" was added to the designated lead to signify this modification.

The remaining letters R, L, and F refer to the respective extremity where the exploring (positive) electrode is recording (R referring to right arm, L to left arm, F to left foot or left leg). As mentioned previously, a unipolar limb lead records the electrical potential at a single exploring (positive) electrode on one of the limbs minus the average potentials of the other two limb leads. For example, lead aVR measures the potential at the RA, minus the average potentials at the LA and LL. Lead aVL, measures the potential at the LA, minus the average potentials at the RA and LL. Lead aVF measures the potential at the LL electrode, minus the average potentials at the RA and left arm LA. Figure 4 illustrates how the unipolar limb leads are generated, as well as the normal waveforms in each lead.

The final six leads in the standard 12-lead ECG are designated as the precordial leads and are also unipolar leads. These leads view the transverse plane of the body from anterior to posterior. Their location across the torso allows these leads a direct view of the right and left ventricles. The three limb leads (RA, LA, LL) are used to create the negative central terminal required for a unipolar lead, and the exploring electrodes labeled VI through V6 serve as the positive (recording) electrodes. Because of the proximity of the precordial leads to the heart, they do not require augmentation; hence there is not a designation as with the augmented limb leads (Macfarlane & Veitch Lawrie, 1989). Figure 5 shows the location of the six precordial leads and the normal waveforms generated from these leads.

[FIGURES 4a-4b OMITTED]

The most commonly printed arrangement of a standard 12-lead ECG is in a 3 x 4 format (Wagner, 1994). The ECG leads in a 3 x 4 format are displayed and printed in the order in which they were invented, with the three bipolar limb leads in the first column, the three augmented unipolar limb leads in the next column, and the six unipolar precordial leads (V1 to V6) in columns 3 and 4 respectively (see Figure 6).

[FIGURE 5 OMITTED]

The 12-lead ECG is ideal and recommended for in-hospital monitoring because multiple areas of the myocardium can be viewed, a point very important for distinguishing arrhythmias and detecting myocardial ischemia (Drew et al., 2004). While 12-lead monitoring is recommended, medical-surgical nurses are likely to encounter lead configurations with fewer than 12 ECG leads (3, 5, or 6 leads, or derived 12-lead configurations). Reasons for differing leads systems include the storage and system capacity offered by individual manufacturers, goals of ECG monitoring, and financial constraints when purchasing monitoring equipment.

Common In-Hospital ECG Monitoring Lead Systems

Three-lead system. The simplest ECG lead configuration available for in-hospital ECG monitoring is the three-lead system. This is a bipolar lead system made up of RA, LA, and LL lead wires (see Figure 3a). This lead configuration allows monitoring of leads I, II, and III, or a modified chest lead (e.g., modified chest lead 1 or MCL1). The latter lead can be obtained by placing the RA and LA leads in the proper location and moving the LL lead to the V1 location (fourth intercostal space to the right of the sternal border). Lead MCL1 often is selected by nurses as a substitute for lead VI, a superior lead for distinguishing ventricular arrhythmias. Important limitations of MCL1 versus a true VI will be discussed (Drew & Ide, 1998; Pelter, Adams, & Drew, 2003)

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Three-lead ECG configurations are seen commonly in telemetry ECG monitoring systems, transport monitor/defibrillators, crash cart monitor/defibrillators, and dated bedside ECG monitors (Drew et al., 2005). This monitoring system is adequate for tracking heart rate, identifying R waves for synchronized direct-current cardioversion, and identifying ventricular fibrillation. However, the three-lead configuration is inadequate for identifying complex arrhythmias or myocardial ischemia (Drew & Ide, 1998; Pelter et al., 2003). For example, distinguishing ventricular tachycardia (VT) versus supraventricular tachycardia (SVT) with aberrancy cannot be done with a three-lead system because a true V1 cannot be obtained. Distinguishing these two rhythms is important because treatment options are very different for VT versus SVT. While a modified V1 or MCL1 can be obtained with this lead configuration, evidence shows that during wide-complex tachycardias, the QRS morphology in MCL1 differs considerably from that of a true V1, making MCL1 inadequate for distinguishing VT versus SVT (Drew & Scheinman, 1995). Lastly, the ability to detect myocardial ischemia is limited significantly when only three leads are used because ST segment changes indicative of ischemia often occur outside these leads (Drew, Pelter et al., 1998; Pelter, Adams, & Drew, 2002).

Five-lead or six-lead system. A common ECG lead system available for in-hospital ECG monitoring is a five-lead or six-lead system (Drew et al., 2005). Included in this system are the four limb leads and one or two chest leads (see Figure 7). These lead configurations are available in both bedside monitoring systems, as might be used in the CCU, and telemetry monitoring systems for use on units where ambulatory monitoring is performed.

This system records the six limb leads (I, II, III, aVR, aVL, aVF) and one (five-lead system) or two (six-lead system) precordial leads. Recommendations for selecting V leads include V1 for the five-lead system, and Vl and V5 for the sixlead system because these are superior leads for arrhythmia and ischemia diagnosis (Drew et al., 2005). While an advantage of the five-lead or six-lead system versus the three-lead system is the ability to monitor a true VI for complex arrhythmias and an additional precordial lead with the six-lead system, the ability to identify myocardial ischemia is still limited (Pelter et al., 2003).

Mason-Likar 12-lead system. Some ECG monitoring companies now offer 12-lead ECG monitoring using the Mason-Likar lead configuration (see Figure 2b). An obvious benefit of this system is that it is possible to monitor all 12-leads, which is ideal for arrhythmia and ischemia monitoring (Drew & Funk, 2006). While 12-lead systems are available, not all ECG monitoring companies have the ability to analyze, store, and print in all 12 ECG leads. Clinicians thus must decide the best leads to monitor, display, and print for each individual patient. Careful consideration of specific monitoring features and capabilities should be discussed carefully when purchasing ECG monitoring systems.

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While the 12-lead ECG is ideal for continuous in-hospital monitoring, the Mason-Likar lead configuration can alter the amplitude and axis of ECG waveforms (Fayn, Rubel, & Macfarlane, 2007). Because criteria for diagnosing cardiac abnormalities, such as chamber enlargement, hypertrophy, axis, prior infarction, and drug effects, are based upon the standard 12-lead ECG, it is not prudent to use 12-lead ECGs obtained from the Mason-Likar lead configuration when making these diagnoses; hence a standard 12-lead ECG still may be required by cardiologists or other clinicians who over-read 12-lead ECGs (e.g., routine morning 12-lead ECG, pre-surgical ECGs, post-MI ECGs, etc.).

[FIGURE 8 OMITTED]

Derived 12-lead ECG. While the Mason-Likar 12-lead configuration is ideal for continuous ECG monitoring, the six precordial leads can interfere with auscultation, echocardiograms, X-rays, and defibrillation during cardiac emergencies (Sejersten et al., 2007). In addition, these leads can be challenging to apply and maintain in men with hairy chests or women with pendulous breasts. With this in mind, investigators reported on deriving a 12-lead ECG using only five electrodes on the body (Dower, Yakush, Nazzal, Jutzy, & Ruiz, 1988) (see Figure 8).

Several investigations comparing the five-lead EASI system to the 12-lead ECG have shown that the EASI lead system is comparable when diagnosing wide complex tachycardias (Drew & Scheinman, 1995), acute myocardial ischemia (Drew, Adams, Pelter, & Wung, 1996; Drew, Adams, Pelter, Wung, & Caldwell, 1997; Drew, Pelter et al., 1998; Sejersten et al., 2007), and other cardiac abnormalities (Drew et al., 1999). The EASI 12-lead ECG system now is available for in-hospital use (Philips Medical Systems, Andover, MA).

As with the Mason-Likar lead configuration, clinicians should be careful when comparing derived 12-lead ECGs to standard 12-lead ECGs as there are subtle differences to waveform amplitudes and axis between the two ECG types (Drew et al., 1999). Despite these limitations, the EASI 5-lead configuration is ideal for in-hospital monitoring because the precordial area is free of skin electrodes and possibly less muscle artifact may appear because there are no electrodes close to any extremity.

Nursing Implications for Medical-Surgical Nurses

Key factors for ensuring high-quality ECG monitoring include proper skin preparation, correct placement of skin electrodes and lead wires, and routine quality improvement assessments.

Skin preparation. A common complaint by nurses using in-hospital ECG monitoring is the high number of false alarms due to artifact or "noisy signal" (Drew, Wung, Adams, & Pelter, 1998). Most of these issues are related to improper skin preparation at the onset of monitoring. This problem can be minimized substantially with careful skin preparation of the patient's torso when initiating monitoring and as needed throughout the monitoring period. According to Adams and Pelter (2005), the following steps should be taken. Skin preparation should include removing hair at sites of electrode placement. Shaving or clipping hair should be done with caution in all patients, but especially those receiving anticoagulants because bleeding can occur from even small abrasions. The next step for prepping the skin should include vigorous removal of skin oil/debris using an alcohol prep pad and/or a washcloth. The skin surface should then be completely dried prior to applying skin electrodes to the body surface. These small steps can minimize poor signal quality, reduce the number of false alarms, and provide clinicians with high-quality ECGs for making important clinical decisions related to patient care.

Skin electrode placement. Valid, reliable ECGs are dependent upon accurate, consistent electrode placement. Because diagnosis of both arrhythmias and ischemia can be altered significantly by inaccurate placement of electrodes (Drew et al., 2004), medical-surgical nurses responsible for ECG monitoring must learn electrode placement and have frequent reassessment for continued competency.

Ideally, following careful skin preparation and prior to application of skin electrodes, each electrode site should be marked with indelible ink to ensure that electrodes are reapplied to the correct location if they are removed accidentally or for procedures (Adams & Pelter, 2005). Correct lead placement is illustrated and described in Table 1. Lead placement can be challenging for obese patients (Saltykova et al., 2006), women with large breasts (Rautaharju, Park, Rautaharju, & Crow, 1998), or in patients with dressings overlying lead locations. Electrodes should be applied as close as possible to the correct location; lead placement at other than the designated location should be noted in the medical record and on ECGs that are printed and placed in the medical record (Drew et al., 2004).

Lead wires. Incorrect attachment of lead wires to skin electrodes can alter ECG waveforms significantly and lead to misdiagnosis. Careful attention should be paid to correct lead wire attachment at the initiation of monitoring, and reassessment should be done routinely by medical-surgical nurses using ECG monitoring.

Lead wires are both labeled and color-coded to assist clinicians. The same label and color coding system must be followed by all manufacturers of ECG monitoring equipment. There are two systems of labeling and color coding: one for use in Europe, recommended by the International Electrotechnical Commission; and one for use in the United States, recommended by the Association for the Advancement of Medical Instrumentation and the American Heart Association (Kligfield et al., 2007). Table 2 shows the labeling and color coding scheme used by each association.

Continuous quality improvement. Continuous quality improvement specific to ECG monitoring should be incorporated into routine quality assessments (Drew et al., 2004). Compliance with any quality assurance measure must include education related to ECG monitoring (goals, lead placement, and ability to recognize ECG abnormalities specific to the patient population of the unit) (Rauen, Chulay, Bridges, Vollman, & Arbour, 2008). Routine assessment of patients for skin preparation, lead placement, and appropriate documentation can be incorporated easily into quality assessments already being done on the unit (pressure ulcer and fall prevention protocols). Staff nurses must be part of this process because they are the change agents of any quality improvement effort. Identified physician champions for ECG monitoring also can serve as important advocates and educators.

Conclusion

Medical-surgical nurses are likely to encounter in-hospital ECG monitoring. While ECG data can enhance patient assessment, it can be intimidating to learn and frustrating to use because of false-positive alarms due to improper skin preparation. Patients can benefit from this technology only if nurses have a clear understanding of the goals of ECG monitoring, are provided education and training (initial and continuing), and have available continuous quality assurance data to maintain and improve their practice. Success requires the efforts of nurse and physician leadership, incorporation of evidence-based information by clinical nurse specialists and clinical leaders, and involvement of staff nurses.

References

Adams, M.G., & Pelter, M.M. (2005). Continuous ST-segment monitoring. In D.J. Lynn-McHale & K.K. Carlson (Eds.), American Association of Critical Care Procedure Manuual for Critical Care (5th ed., pp. 430-437). St. Loius: Elsevier/Sanders.

Day, H.W. (1963). Preliminary studies of an acute coronary care area. Lancet, 83, 53-55.

Dower, G.E., Yakush, A., Nazzal, S.B., Jutzy, R.V., & Ruiz, C.E. (1988). Deriving the 12-lead electrocardiogram from four (EASI) electrodes. Journal of Electrocardiology, 21 (Suppl.), S182-187.

Drew, B.J., Adams, M.G., Pelter, MM., & Wung, S.R (1996). ST segment monitoring with a derived 12-lead electrocardiogram is superior to routine cardiac care unit monitoring. American Journal of Critical Care, 5(3), 198-206.

Drew, B.J., Adams, M.G., Pelter, M.M., Wung, S.F., & Caldwell, M.A. (1997). Comparison of standard and derived 12-lead electrocardiograms for diagnosis of coronary angioplasty-induced myocardial ischemia. American Journal of Cardiology, 79(5), 639-644.

Drew, B.J., Califf, R.M., Funk, M., Kaufman, E.S., Krucoff, M.W., Laks, M.M., et al. (2004). Practice standards for electrocardiographic monitoring in hospital settings: An American Heart Association scientific statement from the Councils on Cardiovascular Nursing, Clinical Cardiology, and Cardiovascular Disease in the Young: Endorsed by the International Society of Computerized Electrocardiology and the American Association of Critical-Care Nurses. Circulation, 110(17), 2721-2746. Drew, B.J., Califf, R.M., Funk, M., Kaufman, E.S., Krucoff, M.W., Laks, M.M., et al. (2005). AHA scientific statement: Practice standards for electrocardiographic monitoring in hospital settings: An American Heart Association Scientific Statement from the Councils on Cardiovascular Nursing, Clinical Cardiology, and Cardiovascular Disease in the Young: Endorsed by the International Society of Computerized electrocardiology and the American Association of Critical-Care Nurses. Journal of Cardiovascular Nursing, 20(2), 76-106.

Drew, B.J., & Funk, M. (2006). Practice standards for ECG monitoring in hospital settings: Executive summary and guide for implementation. Critical Care Nursing Clinics of North America, 18(2), 157-168, ix.

Drew, B.J., & Ide, B. (1998). Differential diagnosis of wide QRS complex tachycardia. Progress in Cardiovascular Nursing, 13(3), 46-47.

Drew, B.J., Pelter, M.M., Adams, M.G., Wung, S.E, Chou, T.M., & Wolfe, C.L. (1998). 12-lead ST-segment monitoring vs single-lead maximum ST-segment monitoring for detecting ongoing ischemia in patients with unstable coronary syndromes. American Journal of Critical Care, 7(5), 355-363.

Drew, B.J., Pelter, M.M., Wung, S.F., Adams, MG., Taylor, C., Evans, G.T., Jr., et al. (1999). Accuracy of the EASI 12-lead electrocardiogram compared to the standard 12-lead electrocardiogram for diagnosing multiple cardiac abnormalities. Journal of Electrocardiology, 32(Suppl.), 38-47.

Drew, B.J., & Scheinman, M.M. (1995). ECG criteria to distinguish between aberrantly conducted supraventricular tachycardia and ventricular tachycardia: Practical aspects for the immediate care setting. Pacing and Clinical Electrophysiology, 18(12 Pt 1), 2194-2208.

Drew, B.J., Wung, S.F., Adams, M.G., & Pelter, M.M. (1998). Bedside diagnosis of myocardial ischemia with ST-segment monitoring technology: Measurement issues for real-time clinical decision making and trial designs. Journal of Electrocardiology, 30(Suppl.), 157-165.

Einthoven, W. (1902). Galvanometrische registratie van het menschilijk electrocardiogram, In S.S. Rosenstein, (Ed). Herinneringsbundel. Leiden: Eduard Ijdo.

Fayn, J., Rubel, R, & Macfarlane, PW. (2007). Can the lessons learned from the assessment of automated electrocardiogram analysis in the common standards for quantitative electrocardiography study benefit measurement of delayed contrast-enhanced magnetic resonance images? Journal of Electrocardiology, 40(3), 246-250.

Fisch, C. (1997). Electrocardiography. In E. Braunwald (Ed.), Heart disease a textbook of cardiovascular medicine (5th ed., pp. 108). Philadelphia: W.B. Saunders Company.

Goldberger, E. (1942). A simple, indifferent, electrocardiographic electrode of zero potential and a technique of obtaining augmented, unipolar, extremity leads. American Heart Journal, 23, 483-492.

Graetunger, J., Packard, J., & Graybiel, A. (1951). A new method of equating the presenting bipolar and unipolar extremity leads on the electrocardiogram: Advantages gained in visualization of their common relationship to the electric field of the heart. American Journal of Medicine, 11, 3-25.

Kligfield, P., Gettes, L.S., Bailey, J.J., Childers, R., Deal, B.J., Hancock, E.W., et al. (2007). Recommendations for the standardization and interpretation of the electrocardiogram: Part I: The electrocardiogram and its technology: A scientific statement from the American Heart Association Electrocardiography and Arrhythmias Committee, Council on Clinical Cardiology; the American College of Cardiology Foundation; and the Heart Rhythm Society: Endorsed by the International Society for Computerized Electrocardiology. Circulation, 115(10), 1306-1324.

Macfarlane, P., & Veitch, L. (1989). Comprehensive electrocardiology (Vol. 11). New York: Pergamon Press. Macfarlane, P., & Veitch Lawrie, T. (1989). The normal electrocardiogram and vectorcardiogram. In P. Macfarlane, and T.D. Veitch Lawrie (Eds.), Comprehensive electrocardiology (Vol. 1, pp. 451-452). New York: Pergamon Press.

Mason, R.E., & Liker, I. (1996). A new system of multiple-lead exercise electrocardiography. American Heart Journal 71(2), 196-205.

Pelter, M.M., Adams, M.G., & Drew, B.J. (2002). Association of transient myocardial ischemia with adverse in-hospital outcomes for angina patients treated in a telemetry unit or a coronary care unit. American Journal of Critical Care, 11(4), 318-325.

Pelter, M.M., Adams, M.G., & Drew, B.J. (2003). Transient myocardial ischemia is an independent predictor of adverse in-hospital outcomes in patients with acute coronary syndromes treated in the telemetry unit. Heart & Lung, 32(2), 71-78.

Rauen, C.A., Chulay, M., Bridges, E., Vollman, K.M., & Arbour, R. (2008). Seven evidence-based practice habits: Putting some sacred cows out to pasture. Critical Care Nurse, 28(2), 98-124.

Rautaharju, P.M., Park, L., Rautaharju, ES., & Crow, R. (1998). A standardized procedure for locating and documenting ECG chest electrode positions: Consideration of the effect of breast tissue on ECG amplitudes in women. Journal of Electrocardiology, 31( 1 ), 17-29.

Saltykova, M.M., Riabykina, G.V., Oshchepkova, E.V., Ataullakhanova, D.M., Lazareva, N.V., Bobokhonova, A.S., et al. (2006). [Electrocardiographic diagnosis of hypertrophy of the left ventricular myocardium in patients with arterial hypertension and overweight]. Terapevticheskii Arkhiv, 78(12), 40-45.

Sejersten, M., Wagner, G.S., Pahlm, O., Warren, J.W., Feldman, C.L., & Horacek, B.M. (2007). Detection of acute ischemia from the EASI-derived 12-lead electrocardiogram and from the 12-lead electrocardiogram acquired in clinical practice. Journal of Electrocardiology, 40(2), 120-126.

Wagner, G. (1994). Marriott's practical electrocardiography In J. Pine (Ed.), (8 ed., pp. 42). Baltimore, MD: Williams & Wilkins.

Wilson, E, Johnson, E, Macloed, A., & Barker, P. (1934). Electrocardiograms that represent the potential variations of a single electrode. American Heart Journal 9, 447-471.

Wilson, E, Johnson, E, & Rosenbaum, EE (1944). The precordial electrocardiogram. American Heart Journal 27.

Wilson, E, Macloed, A., & Barker, P. (1931). The interpretation of the initial deflections of the ventricular complex of the electrocardiogram. American Heart Journal 6, 637-664.

Zipes, D. (1997). Genesis of cardiac arrhythmias: Electrophysiological considerations. In E. Braunwald (Ed.), Heart disease (2 ed., pp. 605 -647). Philadelphia: W.B. Saunders.

Medical and surgical intensive care unit patients suffer from similar types of safety problems and related harm

When it comes to safety problems in the intensive care unit (ICU), the similarity in medical issues faced by critically ill surgical or medical ICU patients may be more important than their differences, suggests the largest ICU safety report project to date. Researchers found that both medical and surgical ICU patients suffered from similar types of safety incidents and related harm. Also, most of these incidents were due to lack of training and teamwork.

About 15% of incidents resulted in physical injury, 10% resulted in longer hospital stays (either expected or actual), and 2% or fewer in death. Nurses reported more than 70% of incidents. About 80% of incidents were considered preventable and more than 40% caused harm. The incidents were reported to patients' family or friends in 18% of cases.

More details are in Sinopoli, D., et al. (2007). Intensive care unit safety incidents for medical versus surgical patients: A prospective multicenter study. Journal of Critical Care, 22, 177-183.

Michele M. Pelter, PhD, RN, is Assistant Professor, Division of Health Sciences, Orvis School of Nursing, University of Nevada, Reno, NV.
Table 1.

Correct Lead Location.
(see Figure 2b for anatomic location)

     Lead                    Anatomic Location

Right Arm (RA)   Infraclavicular fossa close to the right
                   shoulder
Left Arm (LA)    Infraclavicular fossa close to the left
                   shoulder
Right Leg (RL)   Lower right abdomen below the umbilicus
Left Leg (LL)    Lower left abdomen below the umbilicus
V1               4th intercostal space right of the sternal
                   boarder
V2               4th intercostal space left of the sternal
                   boarder
V3               Mid way between [V.sub.2] and [V.sub.4]
V4               5th intercostal space middavicular line
V5               Straight line from [V.sub.4] anterior
                   axillary line
V6               Straight line from [V.sub.4] midaxillary

Table 2.

ECG Lead Wires Color Coding Scheme Recommended for Use in
Europe by the International Electrotechnical Commission (IEC) and for
the United States by the Association for the Advancement of Medical
Instrumentation (AAMI) and the American Heart Association (AHA)
(Kligfield et al., 2007)

  Lead      AAMI/AHA     AAMI/AHA      IEC
Location     Label     Color Coding   Label    IEC Color

Right Arm   RA         White          R       Red
Left Arm    LA         Black          L       Yellow
Right Leg   RL         Green          N       Black
Left Leg    LL         Red            F       Green
Chest       V1         Brown/Red      C1      White/Red
Chest       V2         Brown/Yellow   C2      White/Yellow
Chest       V3         Brown/Green    C3      White/Green
Chest       V4         Brown/Blue     C4      White/Brown
Chest       V5         Brown/Orange   C5      White/Black
Chest       V6         Brown/Purple   C6      White/Violet
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Title Annotation:Clinical 'How To'
Author:Pelter, Michele M.
Publication:MedSurg Nursing
Article Type:Report
Geographic Code:1USA
Date:Dec 1, 2008
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