Obtaining An Electrocardiogram PDF

Lesson 4: Obtaining an Electrocardiogram The Electrocardiogram (ECG or EKG) An electrocardiogram (ECG or EKG) records the electric impulses of the heart by the means of electrodes and a galvanometer (ECG machine). These electrodes are placed on the legs, arms, and chest. Combinations of two...

Lesson 4: Obtaining an Electrocardiogram The Electrocardiogram (ECG or EKG) An electrocardiogram (ECG or EKG) records the electric impulses of the heart by the means of electrodes and a galvanometer (ECG machine). These electrodes are placed on the legs, arms, and chest. Combinations of two electrodes are called bipolar leads (i.e., lead I is the combination of both arm electrodes, lead II is the combination of the right-arm and left-leg electrodes, and lead III is the combination of the left-arm and left-leg electrodes). The unipolar leads are AVF, AVL, and AVR; the A means augmented, V is the voltage, and F is left foot, L is left arm, and R is right arm. There are at least six unipolar chest or precordial leads. A standard ECG consist of 12 leads: six limb leads (I, II, III, AVF, AVL, AVR) and six chest (precordial) leads (V1, V2, V3, V4, V5, V6). Figure10 Standard 12-lead ECG electrode placement With each cardiac cycle or heartbeat, the sinoatrial node (SA or sinus node) sends an electrical impulse through the atrium, causing atrial contraction or atrial depolarization. The SA node is called the pacemaker, because it controls the heart beat. The impulse is then transmitted to the atrioventricular (AV) node and the bundle of His and travels down the ventricles, causing ventricular contraction or ventricular depolarization. When the atria and the ventricles relax, repolarization and recovery occurs. The electrical activity that the ECG records is in the form of waves and complexes: P wave (atrial depolarization); QRS complex (ventricular depolarization); and ST segment, T wave, and Unit wave (ventricular repolarization). An abnormal ECG indicates a disturbance in the electrical activity of the myocardium. A person could have heart disease and have a normal ECG as long as the cardiac problem did not affect the transmission of electrical impulses. 1 P Wave (Atrial Contraction): The normal time is 0.12 seconds or three small blocks. An enlarged P wave deflection could indicate atrial enlargement, which could be the result of mitral stenosis. An absent or altered P wave could suggest that the electrical impulse did not come from the SA node. PR Interval (from the P Wave to the Onset of the Q Wave): The normal time interval is 0.2 seconds or five small blocks. An increased interval could imply a conduction delay in the AV node. It could be the result of rheumatic fever or arteriosclerotic heart disease. A short interval could indicate Wolff-Parkinson-White syndrome. QRS Complex (Ventricular Contraction): The normal time is less than 0.12 seconds or three small blocks. An enlarged Q wave may imply an old myocardial infarction. An enlarged R-wave deflection could indicate ventricular hypertrophy (enlargement). An increased time duration may indicate a bundle-branch block. ST Segment (Beginning Ventricular Repolarization): A depressed ST segment indicates myocardial ischemia (decreased supply of oxygen to the myocardium). An elevated ST segment can indicate acute myocardial infarction or pericarditis. A prolonged ST segment may imply hypocalcemia or hypokalemia. A short ST segment may be due to hypercalcemia. T Wave (Ventricular Repolarization): A flat or inverted T wave can indicate myocardial ischemia, myocardial infarction, or hypokalemia. A tall, peaked T wave (greater than 10 mm or 10 small blocks in precordial leads, or greater than 5 mm or five small blocks in limb leads) can indicate hyperkalemia. 2 Factors Affecting Diagnostic Results  Body movement and electromagnetic interference during the ECG recording could distort the tracing.  Poor electrode-to-skin contact will distort tracing. Clinical Problems Abnormal Findings: Cardiac dysrhythmias, cardiac hypertrophies, myocardial ischemia, electrolyte imbalances (potassium, calcium, and magnesium), myocardial infarction, pericarditis Nursing Implications with Rationale o Record the list of medications the client is taking. The health care provider may want to compare ECG readings to check for improvement and changes; therefore knowing the drugs the client is taking at the time of the ECG would be helpful. Client Teaching  Instruct the client to relax and to breathe normally during the ECG procedure. Tell the client to avoid tightening the muscles, grasping bed rails or other objects, and talking during the ECG tracing.  Tell the client that the ECG should not cause pain or any great discomfort.  Inform the client to tell you if he or she is having chest pain during the ECG tracing. Mark the ECG paper at the time the client is having chest pain.  Allow the client time to ask questions. Refer questions you cannot answer to another health care provider, e.g., physician or cardiologist.  Inform the client that the ECG takes about 15 minutes. 3  OBTAINING AN ELECTROCARDIOGRAM Purpose  Identifies rhythm disturbances, conduction, abnormalities and electrolytes imbalance  Gives information about the size of the heart’s chambers and the heart’s position in the chest  Aids in diagnosing and monitoring such conditions as MI and pericarditis  Can monitor the effects of medications and evaluate the function of an artificial pacemaker. Equipment  ECG machine  ECG strip or paper  Electrodes with gel  4x4 gauze pad or dry and with alcohol cotton balls Goal  A cardiac electrical tracing is obtained without any complications.  To record the heart’s electrical activity or action potential or wave form. ASSESSMENT 1. Review the patient’s medical record and plan of care for information about the patient need for ECG 2. Assess cardiac status 3. Keep the patient away from the objects that might cause electrical interference 4. Inspect the patient’s chest for areas of irritation, breakdown or excessive hair PLANNING 1. Verify the order for an ECG on the patient’s medical record. 2. Gather all equipment and bring to bedside. 3. Perform hand hygiene and put on PPE, if indicated. 4. Identify the patient. 5. Close curtains around bed and close the door to the room, if possible. As you set up the machine to record a 12-leadECG, explain the procedure to the patient. Tell the patient that the test records the heart’s electrical activity, and it may be repeated at certain intervals. Emphasize that no electrical current will enter his or her body. Tell the patient the test typically takes about 5 minutes. Ask the patient about allergies to adhesive, as appropriate. 6. Place the ECG machine close to the patient’s bed, and plug the power cord into the wall power outlet. 7. If the bed is adjustable, raise it to a comfortable working height, usually elbow height of the caregiver (VISN 8Patient Safety Center, 2009). 4 IMPLEMENTATION 1. Have the patient lie supine in the center of the bed with the arms at the sides. Raise the head of the bed if necessary to promote comfort. Expose the patient’s arms and legs, and drape appropriately. Encourage the patient to relax the arms and legs. If the bed is too narrow, place the patient’s hands under the buttocks to prevent muscle tension. Also use this technique if the patient is shivering or trembling. Make sure the feet do not touch the bed’s footboard. 2. Select flat, fleshy areas on which to place the electrodes. Avoid muscular and bony areas. If the patient has an amputated limb, choose a site on the stump. 3. If an area is excessively hairy, clip the hair. Do not shave hair. Clean excess oil or other substances from the skin with soap and water and dry it completely. 4. Apply the limb lead electrodes. The tip of each lead wire is lettered and color coded for easy identification. The red or RA lead goes to the right arm; the black or RL lead to the right leg; the green or LL lead to the left leg; the yellow or LA lead to the left arm. Peel the contact paper off the self-sticking disposable electrode and apply directly to the prepared site, as recommended by the manufacturer. Position disposable electrodes on the legs with the lead connection pointing superiorly. 5. Connect the limb lead wires to the electrodes. Make sure the metal parts of the electrodes are clean and bright. 6. Expose the patient’s chest. Apply the pre-cordial lead electrodes. The tip of each lead wire is lettered and color coded for easy identification. The brown or V1 to V6 leads are applied to the chest. Peel the contact paper off the self-sticking, disposable electrode and apply directly to the prepared site, as recommended by the manufacturer. Position chest electrodes as follows:  V1: Fourth intercostal space at right sternal border  V2: Fourth intercostal space at left sternal border  V3: Halfway between V2 and V4  V4: Fifth intercostal space at the left midclavicular line  V5: Fifth intercostal space at anterior axillary line (halfway between V4 and V6)  V6: Fifth intercostal space at midaxillary line, level with V4 7. Connect the pre-cordial lead wires to the electrodes. Make sure the metal parts of the electrodes are clean and bright. 8. After the application of all the leads, make sure the paper speed selector is set to the standard 25 m/second and that the machine is set to full voltage. 9. If necessary, enter the appropriate patient identification data into the machine. 10. Ask the patient to relax and breathe normally. Instruct the patient to lie still and not to talk while you record the ECG. 11. Press the AUTO button. Observe the tracing quality. The machine will record all 12 leads automatically, recording3 consecutive leads simultaneously. Some machines have a display screen so you can preview waveforms before the machine records them on paper. Adjust waveform, if necessary. If any part of the waveform extends beyond the paper when you record the ECG, adjust the normal standardization to half-standardization and repeat. Note this adjustment on the ECG strip, because this will need to be considered in interpreting the 5  results. 12. When the machine finishes recording the 12-lead ECG, remove the electrodes and clean the patient’s skin, if necessary, with adhesive remover for sticky residue. 13. After disconnecting the lead wires from the electrodes, dispose of the electrodes. Return the patient to a comfortable position. Lower bed height and adjust the head of bed to a comfortable position. 14. Clean ECG machine per facility policy. If not done electronically from data entered into the machine, label the ECG with the patient’s name, date of birth, location, date and time of recording, and other relevant information, such as symptoms that occurred during the recording (Jevon,2007b). 15. Remove additional PPE, if used. Perform hand hygiene. EVALUATION 1. Note for the quality of the ECG obtained DOCUMENTATION 1. Secure the ECG strip to chart 2. Document the patient’s name, age, date and time ECG is obtained. 6