Electrocardiogram or ECG is one of the important diagnostic examination that determines abnormalities in the heart activity of the patient. Among of these heart abnormalities that can ECG identify are those dysrhythmias and alterations in conduction indicative of myocardial damage, enlargement of the heart or drug effects. As one of the Emergency Medical Technician or EMT, it is important for them to know by heart its uses and benefits of knowing and performing the these diagnostic exam to their respective patient. In these paper we will identify the importance and its benefits of acquiring knowledge of performing ECG and also incorporate to these paper are some tips for the EMT on how to perform the diagnostic exam correctly.
Taking an ECG is fairly simple, once one is familiar with the machine and the proper placement of the electrode or leads. It usually takes an experience technician between 5 to 10 minutes to connect the leads to patient and take complete recording. A novice may take double this time, which is also influenced by difficulties in hairy chested individuals, buxom women, restless patients and slipping of suction electrodes in thin chested individuals (Smeltzer & Bare, 2004).
Careful attention to the correct placement of the chest leads is a very important aspect in the technique of ECG recording. A deviation of as such as one interspaced vertically or one centimeter horizontally may results false abnormalities. Also electrical conduction between the skin and the ECG electrodes should be maximized with the use of electrode gel or salt containing solution. In patients who have a lot of grime and oil on the skin, it may necessary to first wipe the skin with alcohol or acetone to ensure adequate contact (Conover, 1998).
The sternal angle, a bony prominence about four to five centimeter below the sternal notch serves as the landmark for the second intercostals space or I.C.S. Lead V1 is located on the fourth (4th )I.C.S immediately to the right of the sternum. V2 is on the 4th I.C.S of the left sternal border. V4 is in the left midclavicular line, in the fifth (5th )interspace, while V3 is midway between V2 and V4. V5 is located in the anterior axillary line while V6 is in the mid axillary line, both at the same level of V4 (Wagners, 2001).
A special leads may be requested. V7 corresponds to the posterior axillary line at the same level as V4, V5, V6. V7 may be requested in cardiac hypertrophy. On the other hand, right sided chest leads are the mirror image of the usually located leads. Therefore, lead V4R is found in right mid clavicular line in the 5th ICS, while V3R is midway between V1 (V2R) and V4R. These may be requested in cases of dexocardia or right ventricular infarction (Wagners, 2001).
These test taking diagnostic examination for the patient is very crucial for EMT to perform, because a one mistake in putting electrodes in a wrong position may indicate a false interpretation of the EMT, thus, this may also think that the client might have an heart attack or dysrhytmias and may wrongly administered medications that might worsen the clients condition. It is very important and it is a responsible for an EMT to know the ECG as well as its correct placement of the electrodes to the patients body. The information below are some guidelines for EMT to know the common errors of performing ECG and how to avoid it. But in the mean time an EMT should know the color code for each electrode and its proper placement (Conover, 1998).
4th Intercostal space
4th Intercostal space
Equidistant between V2 and V4
5th intercostals space Midclavicular line
5th Intercostal space Anterior axillary line
5th intercostals space Midaxillary line
It is very important for EMT to know the common causes of errors in performing these diagnostic examination. Knowing these artifacts, an EMT may readily avoided these situation (Wung &Drew 1999).
1. Mixing up of lead wired is a common error. A clue to the reversal of the two leads is an inversion of the P, QRS and T waves in Lead I. This also results in an interchange of Lead II and III as well as Leads A.V.L (atrioventricukar left) and A.V.R (atrioventicular right).
2. Inaccurate lead placement is another cause for erroneously interpreted tracing. Since tracings taken at intervals are commonly compared, variations in the lead placements may cause the reader to think that gross changes occurred. For example, if V1 is placed in the 3rd ICS instead of 4th ICS, the ECG may show a right bundle branch block pattern (Conover, 1998).
3. Incorrect centering may cause an artificial reduction in the amplitude of the QRS complex or a distortion of normal T wave morphology. These would result in numerous diagnostic errors.
4. Wandering or shifting baseline is another frequent cause of unreadable tracings and diagnostic errors. These artifacts is easily avoidable if enough care is taken.
a. Most frequent cause is impatience in waiting for the stylus to settle down before running the paper at the start of each lead tracing.
b. Movement on the part of an uncomfortable or curious patient.
c. Unnecessary conversation between the patient and the technician
d. And loose or dirty electrodes.
The technician should also observe if the shifting baseline moves in relation to the patient’s breathing so that the latter can be requested to hold his breath for a few seconds while tracing is made (Conover, 1998).
5. Intermittent irregularities of the baseline appears as “jumps” in the baseline tracing and consists of irregular movements which vary in shape and frequency. Quite often, these are due to loose connections or electrical contact between the patient and the electrode, the electrode and the ECG cable or breaks in the electrical wiring of the machine. These may also be caused by loose AC connections or wild voltage fluctuations. The most common cause is movement by the patient either voluntary or involuntary. Voluntary movements occur if the patient is restless, uncomfortable or curious and may be avoided if the patient is properly instructed. Involuntary movements are caused by tremors, coughing or hiccups. While these are inevitably unavoidable, the ECG operator should always indicate on the tracing the presence or such, so that these will not misdiagnosed to be due to extrasystoles.
Helpful Pointers in making a good ECG tracing (Wung & Drew 1999)
Correct standardization will be indicated by a “square wave” which consists of 10 small squares in amplitude. Any distortion in the shape of this square wave would indicate a problem in the “damping” of the stylus, i.e., improper resistance to the movement of the stylus cause too much or too little pressure of the stylus on the ECG paper.
Make sure that the baseline is steady. This can be done by observing the stylus before running the paper. If there are fine vibrations of the baseline, check the grounding. Unplug all other appliances in the room and make sure that the patient is not touching the wall,. Make sure that the electrode/leads are in proper contact with the skin and do not hesitate to add more conducting substance.
Each lead should contain at least 5 complexes of sufficient clarity and similarity. If there is any irregularity in cardiac rhythm, a longer lead tracing may be necessary.
All the ECG complexes should be visible within the printed lines, and the stylus deflection should not reach either the upper or lower border of the paper. IF the amplitude of the complexes exceeds the width of the paper, the sensitivity of machine may be reduced to half. Conversely, complexes which are too small in the normal setting may be magnified by doubling the sensitivity. In both situations, however, one must indicate the new sensitivity setting by introducing a new standardization pulse.
All tracing should be labeled with the patient’s name and date and time that the ECG was taken. Each lead must be identified by writing on the upper or lower margin of each lead tracing
Taking an ECG to patient is very beneficial to them, these simple yet very important machine can determine if the patient is suffering from a recent heart attack, dysrhythmias or arrythmias which is very life threatening for them. With the correct placement of the electrodes and the right interpretation of the ECG graph, we would know the right medication for them.
Conover, M. B. (1998). Pocket Guide to Electrocardiology. St. Louis: Mosby
Smeltzer, S. C. and Bare, B. G. (2004). Brunner and Suddarth’s Textbook of Medical and Surgical Nursing (10th ed.). USA. Lippincott Williams & Wilkins
Wagners, G. S. (Ed.) (2001). Marriott’s Practical Electrocardiography (10th ed.). Philadelphia: Lippincott Williams & Wilkins
Wung, S. and Drew, B. (1999). Comparison of 18-lead ECG and selected body surface potential mapping leads in determining maximally deviated ST lead and efficacy in detecting acute myocardial ischemia during coronary occlusion. Journal of electrophysiology, 32. 30 – 37