Electrocardiogram (ECG): It is a curve graph that uses an electrocardiogram machine to record the changes in electrical activity produced by the heart in each cardiac cycle from the body surface. 2. Teach the use of the electrocardiograph, explain the precautions and operating steps, and then divide the students into groups to practice drawing each other under the leadership of the teacher. Operation precautions: 1. Check whether the power supply voltage matches the specified voltage of the machine. 2. Check the electrocardiograph pen and whether each control knob is in the zero or fixed position. If not, turn it back to the specified position. 3. Check whether the machine, wires and accessories are complete and complete. Operation steps: 1. Explain the significance of electrocardiogram examination to the subject, inform them that the examination is painless and harmless, dispel worries and tension, relax their muscles, and instruct them to lie supine on the examination bed. 2. Connect the ground wire and check again whether the grounding is reliable. 3. Connect the power cord, turn on the power switch, and preheat the machine. 4． Connect the lead wires according to regulations, first expose the subject's bilateral wrists and the upper part of the medial malleolus on both sides, and scrub and degrease with alcohol gauze to make the skin red. Then apply conductive liquid, keep the skin in good contact with the electrode, and place the electrode plate according to the right upper limb → red line, left upper limb → yellow line, left lower limb → green line, right lower limb → black line (this line is connected to the ground wire), chest →The requirements for the white line are fixed. Internationally, the connection method of ECG leads and the location of electrode placement are uniformly stipulated, forming a universal and standardized lead system-conventional leads. Includes: limb leads (6), standard limb leads (3 bipolar leads), unipolar compression limb leads (3) and precordial leads (6 unipolar leads). Chest lead monitoring electrode position: V1, 4th intercostal space on the right edge of the sternum. V2, 4th intercostal space on the left edge of the sternum. The midpoint of the line connecting V3, V2 and V4. V4, the intersection of the left midclavicular line and the fifth intercostal space. V5, level of V4 in the left axillary front line. V6, the level of V4 in the left midaxillary line. V7, the level of V4 in the left posterior axillary line. V8, left scapular line V4 level. V9, level of left paraspinal line V4. V3R~V6R, the right chest is symmetrical with V3~V6. 5. Calibrate the paper feed speed, pen position and temperature of the electrocardiograph, and hit the standard voltage to make it 10mm=1mV after correction. 6． According to the lead knob switch sequence, toggle the switches one by one to record the electrocardiogram of the twelve leads I, II, III, aVR, aVL, aVF, V1, V2, V3, V4, V5, and V6 in order. 7． After the examination, check again for any omissions, artifacts, etc., and mark the name of the lead, the name of the person under examination, and the time of examination on the ECG paper. 8. Turn the lead switch back to the "0" position, turn off the power switch, and remove each lead. 3. Measure various bands, waveforms, cardiac axes, and heart rates on the graphs made, and be familiar with their names and writing methods. (1) Electrocardiogram waveform and the meaning of each part: 1. P wave: represents the electrical potential changes during atrial activation. In a normal electrocardiogram, the P wave in leads I and II is upward, while the P wave in lead aVR is inverted; the P wave in leads aVL, III, V1, and V2 can be upward, inverted, or bidirectional. The normally upward P wave has a smooth top, a time limit of <0.12s, and an amplitude of <0.25mV. 2. The PR interval represents the time it takes for the impulse to pass through the atrium, atrioventricular node, and atrioventricular bundle to reach the ventricle. The normal time limit is 0.12~0.20s. For infants and those with fast heartbeats, the PR interval can be shorter. A prolonged PR interval often indicates atrioventricular block. 3. QRS complex: represents the potential changes during ventricular activation. The normal QRS complex time is 0.12s. In the limb leads, the absolute value of the QRS wave complex amplitude in each lead adds up to ≥0.5mV. If <0.5mV, it is called low voltage. The sum of the absolute values ??of the QRS wave amplitudes in each lead of the chest leads should be ≥0.8mV. In the chest lead, the R wave of V1 is generally ≤1.0mV, and the R wave of V5 is generally ≤2.5mV. If the voltage is too high, it often indicates ventricular hypertrophy. 4． J point: The junction point between the end of the QRS complex and the beginning of the ST segment.

5. ST segment: starts from the end of the QRS complex to the beginning of the T wave. It represents the slow repolarization of the ventricle. It should be at the zero potential line and can be slightly shifted upward or downward (downward shift ≤ 0.05mV, upward ≤ 0.1mV, but at The upward shift in leads V1 and V2 can reach 0.3mV, V3≤0.5mV). If the ST segment shifts up and down beyond the normal range, it can be seen in heart disease, etc. 6． T wave: represents the voltage change during rapid ventricular repolarization. Under normal circumstances, the direction of the T wave is consistent with the direction of the main wave of the QRS complex (for example, the T wave is inverted in lead aVR, while the T wave in lead V5 is upward). The T wave amplitude is generally 0.2~0.6mV in the limb leads, and may be as high as 1.2~1.5mV in the chest leads. Generally, the T wave amplitude should not be less than 1/10 of the R wave in the same cardiac cycle. The significance of T wave changes needs to be explained in conjunction with clinical data, and is generally seen in myocardial lesions. 7． QT interval: represents the time from the beginning of ventricular activation to the completion of repolarization. This period changes with the heart rate. A fast heart rate means a short QT interval; a slow heart rate means a long QT interval. The normal range is 0.32~0.44s. QT interval prolongation may occur in cardiomyopathy. 8. U wave: It is a lower wave after the T wave. The formation mechanism is not yet clear. The general direction is consistent with the T wave and should be lower than the T wave, usually no more than 0.05mV. However, the U wave in lead V3 can sometimes reach 0.3mV. When the U wave is particularly obvious, it can be seen in hypokalemia. (2) Measurement and analysis methods of electrocardiogram: 1. Measurement of amplitude and time limit: A series of squares of various sizes are printed on the electrocardiogram paper, consisting of horizontal and vertical lines. The gap between the horizontal lines is 1mm, and 1mm is equal to 0.1mV. Every five horizontal lines have a thicker horizontal line, which represents 0.5mV. The horizontal line is used to measure the amplitude of the electrocardiogram wave, that is, the voltage (usually mm or mVlt;, /SPANgt;) express). The interval between vertical lines is 1mm, which is equivalent to 0.04s. There is a thick line for every five vertical lines. The time between two thick lines is 0.2s. The time limit of each wave segment of the electrocardiogram is expressed in seconds. The electrocardiogram was measured using a two-legged minute gauge. 2. Methods for analyzing ECG: ⑴ Arrange each ECG lead according to standard limb leads, pressurized unipolar limb leads and chest leads. Check whether the quality of the electrocardiogram trace is intact and whether there are any omissions or artifacts. ⑵ Analyze whether there is a P wave in each cardiac cycle, whether the relationship between P wave and QRS complex is normal, and determine the rhythm of the heart. ⑶ Analyze the shape and duration of the QRS wave complex to determine whether it is a supraventricular shape (normal shape) or a ventricular shape (abnormal, wide), or differential intraventricular conduction. ⑷ Analyze the relationship between P wave and QRS wave, and determine whether the atrioventricular conduction relationship and conduction time are fixed, not fixed, or completely unrelated. ⑸ Analyze the regularity of the rhythm of P waves and QRS complexes, whether they appear early or late, and judge whether the rhythm is abnormal based on their morphological characteristics and the P-R relationship. ⑹ Analyze the PR interval, ST segment, QT interval and T wave shape and direction to determine whether there is damage to the myocardium or ischemia, electrolyte imbalance, drug effects, etc. (3) How to write an electrocardiogram report: 1. Fill in the general items and clinical diagnosis according to the application form. 2. According to the measurement and analysis method of electrocardiogram, the atrial rate, ventricular rate, PR interval, QT interval, whether P-QRS-T occurs sequentially, etc. are measured to determine the heart rhythm, and the cardiac axis is measured. Heart rate calculation method: Divide 60 seconds by the P-P interval to get the heart rate per minute. For example, if the P-P interval is 0.8 seconds, then the heart rate = 60÷0.8 = 75 beats/minute. In case of arrhythmia such as atrial fibrillation, count the number of QRS complexes within 3 seconds and multiply by 20 to obtain the ventricular rate per minute. Atrial rate can be measured using the same method. 3. Accurately and briefly write down the characteristics of electrocardiogram by analyzing the shape and size of P wave and QRS wave and the relationship between them, as well as ST segment, T wave and QT interval. 4． Summarize the above characteristics of the electrocardiogram and write down the diagnostic opinions of the electrocardiogram, which can be roughly divided into: Rhythm (heart rhythm) Electrocardiographic axis deviation Whether or not, pay attention to the degree if necessary. The electrocardiogram is normal. No, the electrocardiogram is normal. The electrocardiogram is generally normal. The electrocardiogram is suspicious. Abnormal electrocardiogram (list the name of the abnormality) )5. For controversial issues, you can write two diagnoses or suggestions at the end, and then sign.

[Practice method] 1. Practice how to operate the electrocardiograph. 2. Measure the normal electrocardiogram, record it while analyzing it, write a complete report and submit it to the teacher for correction. [Attachment] Normal electrocardiogram indicators: Adult normal value P wave

Voltage: <0.25mV, time limit: <0.12s

PR interval

0.12s- 0.2s

QRS wave group

Time limit: <0.10s, Q wave: <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

Upward shift: V1-V3＜3mm, other leads＜1mm, downward shift:＜0.5mm

T wave

Height should be >1/10R

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