Electrocardiogram (electrocardiogram, ECG): is the use of electrocardiogram machine from the surface of the body to record each cardiac cycle of the heart produced by the electrical activity of the curve graph. Second, show and teach the use of electrocardiogram machine, explain the precautions, operation steps, and then the students in small groups, led by the teacher, the students make graphs each other practice. Operation precautions: 1. check the power supply voltage and the machine voltage is consistent. 2. check the electrocardiogram machine brush, each control knob are in zero or fixed position, if not to be rotated back to the prescribed position. 3. check the machine and wires, accessories are complete, intact. Operation steps: 1. Explain the significance of electrocardiogram examination to the examinee, tell the examinee that there is no pain, no damage, dispel worries, eliminate tension, make his/her muscles relax, and ask him/her to lie on the examination bed on his/her back. 2. Connect the ground wire and check whether the grounding is reliable again. 3. Connect the power cord, turn on the power switch, and warm up the machine. 4. Connect the lead wires according to the regulations and firstly, expose the examinee's bilateral wrists and upper part of the medial ankles. The upper part of the inner ankle is exposed and scrubbed with alcohol gauze to degrease the skin and make it red. Then apply the conductive liquid to keep the skin in good contact with the electrodes, and fix the electrode plate in accordance with the requirements of the right upper limb → red line, the left upper limb → yellow line, the left lower limb → green line, the right lower limb → black line (this line is connected to the ground line), and the chest → white line. Internationally, the connection method of ECG leads and the position of electrode placement have been standardized, forming a common standardized lead system - conventional leads. Including: limb leads (6), standard limb leads (3 bipolar leads), unipolar pressurized limb leads (3) and chest leads (6 unipolar leads). Chest lead monitoring electrode positions: V1, 4th intercostal space at the right edge of the sternum; V2, 4th intercostal space at the left edge of the sternum; V3, midpoint of the line connecting the two points of V2 and V4; V4, the intersection of the left midclavicular line and the 5th intercostal space; V5, left anterior axillary line at the level of V4; V6, left midaxillary line at the level of V4; V7, left posterior axillary line at the level of V4; V8, left scapulae line at the level of V4; V9, left parasternal line at the level of V4; V3R~V6R, right chest and V4 level; V6R~V6R, left chest and V4 level. V6R, right chest symmetrical to V3~V6. 5. Correct the travel speed, position of the brush and temperature of the ECG machine, and strike the standard voltage, corrected so that it is 10mm=1mV. 6. Toggle the switches one by one according to the lead knob switch sequence, and record the ECG of the twelve leads of Ⅰ, Ⅱ, Ⅲ, aVR, aVL, aVF, V1, V2, V3, V4, V5, and V6 in order. After checking, check again for omission, pseudo-differences, etc., and mark the ECG paper with the name of the lead, the name of the person being checked and the time of checking. 8. Rotate the lead switch back to the "0" position, turn off the power switch, and then remove each lead. 9. Measurement of various bands, waveforms, electrocardiogram axes and heart rates, and familiarize yourself with their names and writing methods. (I) ECG waveforms and the significance of each part: 1. P-wave: represents the potential change during atrial agitation. Normal electrocardiogram I, II lead P wave upward, and aVR lead P wave inverted; aVL, III and V1, V2 and other leads P wave can be upward, inverted, or bidirectional. The normal upward P wave is rounded at the top, with a time limit of <0.12s and an amplitude of <0.25mV.2. The PR interval indicates the time for the excitation to reach the ventricle through the atria, AV node, and atrioventricular bundle. The normal time limit is 0.12~0.20s, and the PR interval can be shorter in infants and people with rapid heartbeat, and the prolongation of PR interval often represents atrioventricular block. 3. QRS wave cluster: It represents the change of potential during ventricular excitation. Normal QRS wave group time <0.12s. In the limb leads, the absolute value of each lead QRS wave group amplitude adds up to ≥0.5mV, if <0.5mV is called low voltage. The absolute value of the amplitude of QRS wave in each lead of chest lead should be ≥0.8mV. In chest lead, the R wave of V1 is generally ≤1.0mV, and the R wave of V5 is generally ≤2.5mV, and if the voltage is too high, it is often suggestive of ventricular hypertrophy.4. J-point: the point where the end of the QRS wave group meets the beginning of the ST-segment.5. ST-segment: it begins at the end of the QRS wave group and starts from the beginning of the T-wave, representing the ventricle's slow repolarization, and it should be at the zero potential line, which may be slightly upward or upward, or at the zero potential line, and it should be at the zero potential line, which may be slightly upward or upward. ST segment: from the end of QRS wave group to the beginning of T wave, it represents the slow repolarization of the ventricle and should be at the zero potential line, and can be slightly shifted upward or downward (downward shift ≤ 0.05mV, upward shift ≤ 0.1mV, but upward shift can be up to 0.3mV in V1 and V2 leads, and ≤ 0.5mV in V3 leads). If the upward and downward deviation of ST segment exceeds the normal range, it can be seen in heart disease, etc. 6. T-wave: represents the voltage change during rapid repolarization of the ventricle. Under normal circumstances, the direction of T wave is consistent with the main wave direction of QRS wave group (e.g., T wave is inverted in aVR lead, while T wave is upward in V5 lead). The amplitude of T wave is generally 0.2-0.6mV in limb lead, and may be as high as 1.2-1.5mV in thoracic lead, and the amplitude of T wave should not be less than 1/10 of the R wave in the same cardiac cycle. The significance of the change of T wave needs to be interpreted together with the clinical data, and it can be seen in cardiac myopathy in general. The significance of T-wave changes needs to be interpreted in the context of clinical data and is usually seen in cardiomyopathy. 7. QT interval: represents the time between the onset of ventricular excitation and the completion of repolarization, which varies according to the rate of the heart beat. If the heart rate is fast, the QT interval is short; if the heart rate is slow, the QT interval is long. The normal range is 0.32~0.44s. Prolonged QT interval can be seen in cardiomyopathy.8. U wave: It is a lower wave after T wave, and the formation mechanism is not well understood. The general direction is the same as T wave, and it should be lower than T wave, usually not more than 0.05mV, but the U wave in V3 lead sometimes can be up to 0.3mV, and the U wave can be seen in hypokalemia when it is especially obvious. (ii) Measurement and analysis methods of ECG: 1. Measurement of wave amplitude and time limit: ECG paper is printed with a series of squares of different sizes, consisting of horizontal and vertical lines. The gap between the horizontal lines is 1mm, 1mm is equal to 0.1mV, every five horizontal lines have a thicker horizontal line, representing 0.5mV, the horizontal line is used to measure the amplitude of the electrocardiogram wave that is the voltage (usually in mm or mV<, /SPAN> to indicate). The interval between the vertical lines is 1mm, which is equivalent to 0.04s, and there is one thick line for every five vertical lines, and the time between the two thick lines is 0.2s. The time limits of each wave and segment of the ECG are expressed in seconds. Measurement of the ECG was carried out with a small two-legged dividing gauge.2. Methods of analyzing the ECG: (1) Arrange the ECG of each lead according to the standard limb lead, the pressurized unipolar limb lead and the chest lead. Check whether the quality of ECG tracing is intact, and whether there are omissions and pseudo-differences. (2) Analyze each cardiac cycle for the presence of P waves and the normal relationship between P waves and QRS wave clusters to determine the rhythm of the heart. (3) Analyze the morphology and timing of the QRS wave clusters to determine whether they are supraventricular (normal morphology) or ventricular (aberrant, wide) or intraventricular differential conduction. (4) Analyze the relationship between the P wave and the QRS wave to determine the interatrial conduction relationship, the timing of the conduction, whether it has a fixed relationship, an irregular relationship, or is completely unrelated. (5) Analyze the regularity of the rhythms of P waves and QRS waves, whether they appear earlier or later, and determine whether the rhythms are abnormal according to their morphologic characteristics and the relationship between P-R. (6) Analyze the morphology and direction of PR interval, ST segment, QT interval and T wave to determine whether there is any damage to the myocardium or ischemia, electrolyte disorders, and drug effects. (iii) Method of writing ECG report: 1. Fill in the general items and clinical diagnosis according to the application form. 2. According to the measurement and analysis method of ECG, measure the atrial rate, ventricular rate, PR interval, QT interval, whether P-QRS-T occurs sequentially, etc. to determine the heart rhythm, and measure the electrocardiographic axis. 3. Heart rate is calculated by dividing 60 seconds by the P-P interval to obtain the heart rate per minute. For example, if the P-P interval is 0.8 seconds, the heart rate is 60 ÷ 0.8 = 75 beats per minute. In case of arrhythmia such as atrial fibrillation, count the number of QRS wave clusters in 3 seconds and multiply by 20 to get the ventricular rate per minute. The same method can be used to measure the atrial rate. 3. Through the analysis of the morphology and size of P waves, QRS waves and their relationship, as well as ST segments, T waves and QT intervals, accurately and briefly write down the characteristics of the ECG. 4. Summarize the above characteristics of the ECG, write down the diagnostic opinion of the ECG, which can be roughly divided into: rhythm (rhythm) ECG axis deviation or not, and if necessary, pay attention to the number of degrees of the ECG is normal or not ECG normal ECG normal ECG is generally normal ECG is suspicious ECG is abnormal (list the names of abnormalities) 5. For controversial issues, two diagnoses or recommendations can be written at the end and then signed. ［Practical Methods] I. Practice how to operate the ECG machine. Measure the normal electrocardiogram, analyze and record it, write a complete report and submit it to the teacher for correction. ［Normal electrocardiogram indexes: Adult normal value P wave
Voltage: <0.25mV, time limit: <0.12s
PR interval
0.12s-0.2s
QRS wave cluster
Time limit: <0.10s, Q wave: <0.04s, voltage: aVF <2mV, aVF <2mV, aVF <2mV, aVF <0.04s ＜Voltage: aVF<2mV, aVR<0.5mV, RV 1<1.0mV, RV 5<2.5mV, V1R/S<1, V5R/S>1, RV1+SV5<1.2mV, RV5+SV1<4.0mV, Q wave<1/4R
ST segment
Upshift: V1-V3<3mm, other leads<1mm, downshift: <1mm. 0.5mm
T wave
Height should be >1/10R
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