Electrocardiogram: 12 Lead (Ambulatory) - CE
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Ensure the proper placement of electrodes to avoid incorrect interpretation of the 12-lead electrocardiogram (ECG), mistaken diagnosis, or patient mismanagement.undefined#ref2">2
The standard 12-lead ECG is the most widely used noninvasive diagnostic tool in the management of cardiac disease and is a source of information about the heart’s electrical system.2 The ECG has significant impact on medical decision-making, clinical management, and therapy. Common uses include diagnosing acute coronary syndromes, identifying arrhythmias and conduction disturbances, and determining the effects of medications or electrolytes on the heart’s electrical system (Box 1).
The ECG leads are the standard limb leads (I, II, III); augmented limb leads (augmented vector right [aVR], augmented vector foot [aVF], and augmented vector left [aVL]); and six chest leads (V1 to V6). The standard and augmented leads view the heart from the vertical or frontal plane (Figure 1), and the chest leads view the heart from the horizontal plane (Figure 2). The graphic display consists of the P, Q, R, S, and T waves, which represent electrical activity in the heart.2
If myocardial ischemia or injury is suspected, serial ECGs are performed. Correct standardized electrode placement is crucial for accurate ECG interpretation.3 Advances in technology allow online or wireless transmission, networking capabilities, and computerized interpretation of the 12-lead ECG.
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Rationale: Checking the cables and lead wires helps detect conditions that may give an inaccurate ECG tracing.
If equipment is damaged, obtain alternative equipment and notify the appropriate health care team member for repair.
Rationale: Equipment may require a self-test and warm-up time. Multichannel machines (Figure 3) may require input of information (e.g., data about the patient) to store the ECG appropriately.
Follow the manufacturer’s recommendations and requirements for inputting information and warm-up time.
Rationale: The supine position provides adequate support for the patient’s limbs so muscle activity is minimal. Touching side rails or a footboard may increase the chance of distorting the tracing. Body position changes can also cause alterations in the ECG tracing.
The supine position is best, but Fowler or other positions may be used for comfort. Ensure that serial ECGs are recorded with the patient in the same position, so changes in body position do not cause changes in tracings. If another position is required clinically, document the position on the tracing or in the comment space of the machine input.
Rationale: A lack of privacy may induce anxiety, which can alter the ECG reading. Shivering interferes with the recording.
Rationale: Identifying and marking the lead sites ensures that the electrodes are accurately placed.
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.1
Do not use alcohol for skin preparation because it can dry the skin.1
To ensure good skin contact with the electrodes, clip chest hair with surgical clippers as necessary.
Rationale: Preparing the electrodes allows appropriate impulse conduction.
Ensure that the gel is moist. Replace the electrodes if they are not moist.
Replace adhesive electrodes if they are not sticky.
Rationale: Accurate placement ensures correct electrical tracing of the heart from the vertical and frontal planes.2
Rationale: Accurate placement ensures correct electrical tracing of the heart from the horizontal plane. Slight alterations in the position of a precordial lead may alter the ECG significantly and can have an impact on diagnosis and treatment.2
Rationale: The sternal angle helps identify the second rib for placement of precordial leads in the appropriate intercostal spaces (ICSs).
Variations in precordial lead placement can result in important diagnostic errors, such as septal ischemia or infarction.2
If leads cannot be accurately placed, clearly document the actual location of the electrode placement on the 12-lead ECG.
Place precordial electrodes under the breasts of a patient with large breasts.
Rationale: For correct interpretation, the ECG must be marked accurately and have a clear baseline without artifact.2
Rationale: A rhythm strip is a long recording of a specific lead; lead II is commonly used because P waves are best seen in lead II.
Refer to the manufacturer’s instructions for use (IFU) on obtaining a rhythm strip.
Rationale: A comparison helps determine normal and abnormal findings.
Examine the ECG and determine whether the recording must be repeated while the patient is still connected to the machine.
Rationale: An evaluation identifies pathophysiologic processes that may require further evaluation or treatment.
Follow the manufacturer’s IFU and the organization’s practice for electrode use and removal.
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