Difference between lead 1 and lead 2 ecg placement
Apply lead 1 to the left arm. We suggest the front of the left shoulder in a place where there is little muscle or muscle movement, to avoid any. 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. In the lead II configuration, the positive electrode is on the left leg and the negative electrode is on the right arm. Lead III has the positive electrode on. FEROZ FRAMROZE FOREX NEWS
Approximately 4 centimeters below this, there is a ridge. This identifies the second intercostal space. Feeling down, you will come across the third and fourth intercostal spaces. Use a skin-safe marker to mark the fourth intercostal space as V2. Mark V1 in the mirror position on the opposite side of the chest. V4 can be found one intercostal space lower than V2, in line with the middle of the clavicle.
Mark V4 with your skin safe marker. Next, track along the torso to the subject's left to find V6 at mid auxiliary on the same level as V4. Mark V6. V5 can be marked at midway between V4 and V6. Likewise, mark V3 midway between V2 and V4. You should now have 6 marks for V1 to V6. Apply electrodes to the chest at V1 - V6 Apply your electrodes to your 6 marks!
Connect wires from V1 to V6 to the recording device The 6 electrode wires can now be connected to your recording device. Apply limb leads Apply lead 1 to the left arm. We suggest the front of the left shoulder in a place where there is little muscle or muscle movement, to avoid any EMG signal disturbance.
Next, apply lead 2 to the right arm. Again, the front of the shoulder is suggested here, in a place with little or no muscle or movement. Then connect the left leg. Place the electrode slightly above the ankle. Apply the LA electrode close to the left shoulder below the clavicle. Apply the RL electrode just below the rib cage on the right side. Apply the LL electrode just below the rib cage on the left side. Rationale: Only one precordial lead may be displayed.
Placement of the electrode identifies the lead used. Set the lead selector to monitor the appropriate leads. Six-lead system Apply the RA electrode close to the right shoulder below the clavicle. Apply the chest lead electrode on the V1 position at the fourth ICS right sternal border.
Apply the second chest lead electrode on the V6 position at the fifth ICS left midaxillary line. Place the A red electrode on the left midaxillary line at the level of the fifth ICS. Place the S black electrode on the upper part of the sternum. Place the I white electrode on the right midaxillary line at the level of the fifth ICS. Place the fifth ground electrode anywhere on the patient's chest.
Reduce tension on the lead wires and cables. Rationale: Reducing tension alleviates undue stress on wires and cables that may cause interference or faulty recordings. For hardwire monitoring, fasten the lead wire and patient cable to the patient's gown, making a stress loop. Rationale: Creating a stress loop minimizes pulling on the electrodes, which may be uncomfortable for the patient.
For telemetry monitoring, secure the transmitter in a pouch or pocket in the patient's gown. 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. Obtain an ECG strip and interpret it for rhythm, rate, presence and configuration of the P waves, length of the PR interval, width of the QRS complexes, presence and configuration of the T waves, length of the QT intervals, presence of extra waves e. 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. Set the ST segment parameters, if indicated and available.
Set the QT-interval monitoring, if indicated and available. Discard supplies, remove PPE, and perform hand hygiene. Document the procedure in the patient's record. Obtain a rhythm strip on admission, every shift per the organization's practice , and with rhythm changes. Rationale: A clear pattern is required to make accurate judgments about the patient's status and treatment.
Assess the patient's tolerance of the changes and provide prompt nursing intervention. Rationale: Changes in the ECG pattern may indicate significant problems and require immediate intervention or additional diagnostic tests e. Monitor the skin for an allergic reaction to the adhesive or gel.
Evaluate skin integrity around the electrodes daily. Rationale: Skin integrity must be maintained for a clear picture of the ECG.
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This is the 2nd intercostal space. Gently move your fingers over the 3rd rib to the 3rd intercostal space, and then over the 4th rib to the 4th intercostal space. The electrode is placed here 4th intercostal space right sternal border. Placement of Lead V2 Since you have placed lead V1, you can now put the electrode for lead V2 at the same level to the left side of the sternum 4th intercostal space, left sternal border.
You could also follow the same instructions for V1, but again place the lead on the left side of the sternum. Placement of Lead V4 V4 should be placed before lead V3. First, identify the midclavicular line. This is the midpoint of the left clavicle collarbone. Start by finding the suprasternal notch at the top of the sternum breastbone. Move your finger slightly to the left to find the end medial edge of the clavicle.
Put your fingers from the other hand on the outside of the left shoulder. Move them slightly forward and to the midline about half an inch to find the distal end of the left clavicle. From there, imagine the midpoint on the clavicle and mark it visually or with a finger. Imagine all line running straight down from this point on the clavicle.
From the intercostal space associated with V2 4th intercostal space , move your fingers down over the 5th rib to the 5th intercostal space. Place lead V4 in the 5th intercostal space, in the midclavicular line.
Placement of Lead V5 To place the electrode for lead V5 start in the intercostal space associated with lead V4 5th intercostal space and move to the left to an imaginary line associated with the front portion of the armpit going down toward the anterior hip. Hence, V5 is in the 5th intercostal space, anterior axillary line. Electric potential difference is defined as a difference in electric potential between two measurement points. In electrocardiology these measurement points are the skin electrodes.
Thus, the electrical potential difference is the difference in the electrical potential detected by two or more electrodes. In the previous discussion it was clarified how de- and repolarization generates electrical current. It was also explained that the electrical currents are conducted all the way to the skin, because the tissues and fluids surrounding the heart, indeed the entire human body, acts as electrical conductors. By placing electrodes on the skin it is possible to detect these electrical currents.
The electrocardiograph ECG machine compares, amplifies and filters the electrical potential differences recorded by the electrodes and presents the results as ECG leads. Each ECG lead is presented as a diagram sometimes called a curve. The lead ECG offers outstanding possibilities to diagnose abnormalities. Importantly, the vast majority of recommended ECG criteria e.
The lead ECG displays, as the name implies, 12 leads which are derived by means of 10 electrodes. Three of these leads are easy to understand, since they are simply the result of comparing electrical potentials recorded by two electrodes; one electrode is exploring, while the other is a reference electrode. In the remaining 9 leads the exploring electrode is still just one electrode but the reference is obtained by combining two or three electrodes.
At any given instant during the cardiac cycle all ECG leads analyze the same electrical events but from different angles. For some purposes e. On the other hand, for the purpose of diagnosis morphological changes e. The lead ECG is a trade-off between sensitivity, specificity and feasibility. Obviously, having leads which has been tested in several studies on acute myocardial infarction would improve sensitivity for many conditions, at the expense of specificity and certainly feasibility.
The other extreme, using only one lead would allow for diagnosing several arrhythmias but certainly not all and more importantly it would not allow one to diagnose morphological changes in the heart. Later on it will become clear as to why multiple leads are necessary to diagnose morphological changes. The ECG paper The electrocardiograph presents one diagram for each lead.
Voltage is presented on the vertical Y axis and time on the horizontal X axis of the diagram. The ECG paper has small boxes thin lines and large boxes heavy lines. Small boxes are squares of 1 mm2 and there are 5 small boxes inside each large box. Refer to Figure With normal gain calibration 10 mm on the vertical axis corresponds to 1 mV. Thus, 1 mm corresponds to 0.
Anyone aiming to become proficient in ECG interpretation must master any paper speed. This figure should be studied carefully and attention should be paid to differences on the X-axis there are no difference with respect to the Y-axis.
Figure The ECG grid. As evident from Figure 1 small box 1 mm is 0. The reader should know these differences as it is often necessary to manually measure the time duration of various waves and intervals on the ECG.
Derivation of the ECG leads Every lead represents differences in electrical potentials measured in two points in space. The simplest leads are composed using only two electrodes. The electrocardiograph defines one electrode as exploring positive and the other as reference negative electrode. In most leads, however, the reference is actually composed of a combination of two or three electrodes.
Regardless of how the exploring electrode and the reference is set up, the vectors have the same impact on the ECG curve. Please refer to Figure The electrocardiograph generates an ECG lead by comparing the electrical potential difference in two points in space. In the simplest leads these two points are two electrodes illustrated in this figure. One electrode serves as exploring electrode positive and the other as the reference electrode.
The electrocardiograph is constructed such that an electrical current traveling towards the exploring electrode yields a positive deflection, and vice versa. Anatomical planes and ECG leads The electrical activity of the heart can be observed from the horizontal plane and the frontal plane. The ability of a lead to detect vectors in a certain plane depend on how the lead is angled in relation to the plane, which in turn depend on the placement of the exploring lead and the reference point.
For pedagogical purposes, consider a lead with one electrode placed on the head and the other electrode placed on the left foot. The angle of this lead would be vertical, from the head to the foot. This lead is angled in the frontal plane and it will primarily detect vectors traveling in that plane.
Refer to Figure 17 panel A. Now consider a lead with an electrode placed on the sternum and the other electrode placed on the back on the same level. This lead will be angled from the back to the anterior chest wall, which is the horizontal plane. This lead will primarily record vectors traveling in that plane.
A schematic illustration is provided in Figure Refer to Figure 17 panel B. Schematic view of the angle of limb and chest leads. These leads are therefore excellent for detecting vectors traveling in the frontal plane. The chest precordial leads V1, V2, V3, V4, V5 and V6 have the exploring electrodes located anteriorly on the chest wall and the reference point located inside the chest.
Hence, the chest leads are excellent for detecting vectors traveling in the horizontal plane. The remaining nine leads use a reference which is composed of the average of either two or three electrodes. This will be clarified shortly. The organization of the limb leads. Note that the electrode on the right leg is not included in any lead, but serves as a ground wire. Lead aVR can be inverted into lead —aVR which is recommended as it may facilitate interpretation.
Given the electrode placements, in relation to the heart, these leads primarily detect electrical activity in the frontal plane. Figure 18 shows how the electrodes are connected in order to obtain these six leads. To explain derivation of the limb leads, lead I and lead aVF will be used as examples.
Considering lead I the electrode on the right arm serves as the reference, whereas the electrode on the left arm serves as the exploring electrode. This means that a vector moving from right to left should yield a positive deflection in lead I. In lead aVF the electrode on the left leg serves as exploring electrode and the reference is actually composed by computing the average of the arm electrodes. The average of the arm electrodes yields a reference directly north of the left leg electrode.
Thus, any vector moving downwards in the chest should yield a positive wave in lead aVF. The same principles apply to lead aVR and lead aVL. Lead II, aVF and III are called inferior limb leads, because they primarily observe the inferior wall of the left ventricle Figure 18, coordinate system in upper panel.
Lead aVL, I and —aVR are called lateral limb leads, because they primarily observe the lateral wall of the left ventricle. Note that lead aVR differs from lead —aVR discussed below. All six limb leads are presented in a coordinate system, which the right hand side of Figure 18 panel A shows. To eliminate this gap, lead aVR can be inverted into lead —aVR. It turns out that this is actually meaningful, as it facilitates ECG interpretation e. Whether lead aVR or —aVR is presented depends on national traditions.
A more detailed discussion on the limb leads follow. Lead I compares the electrode on the left arm with the electrode on the right arm, of which the former is the exploring electrode. Lead II compares the left leg with the right arm, with the leg electrode being the exploring electrode.
Lead III compares the left leg with the left arm, with the leg electrode being the exploring one. In clinical electrocardiography this means that the amplitude of, for example, the R-wave in lead II is equal to the sum of the R-wave amplitudes in lead I and III. It follows that we need only know the information in two leads in order to calculate the exact appearance of the remaining lead.
Hence, these three leads actually carry two pieces of information, observed from three angles. In these leads the exploring electrode is compared with a reference which is based on an average of the other two limb electrodes. The letter a stands for augmented, V for voltage and R is right arm, L is left arm and F is foot. In aVR the right arm is the exploring electrode and the reference is composed by averaging the left arm and left leg.
Lead aVR can be inverted into lead —aVR which means that the exploring and reference point has switched positions , which is identical to aVR but upside-down. Despite these advantages lead aVR is unfortunately still used in the United States and many other countries.
We recommend the use of —aVR but for the purpose of this course we will frequently present both leads. If only one of these leads is shown, the reader may simply turn it upside-down to get a view of the desired lead. In lead aVF the exploring electrode is placed on the left leg, so this lead observes the heart directly from south.
Anatomical aspects of the limb leads II, aVF and III: are called inferior diaphragmal limb leads and they primarily observe the inferior aspect of the left ventricle.
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