第四篇 器械检查 第一章 心电图（ Electrocardiogram ） 吕卓人 第一节 临床心电学的基本知识 第二节 心电图的测量和正常值 1 ．了解心电图产生的原理 2 ．熟悉常用导联、正常心电图各波的图 像、正常参考值 3 ．熟悉有关心电图诊断的常用英语词汇

Questions Why ECG could be served for the diagnosis of some diseases? How does ECG work? What is ECG? What is normal ECG? A real case with chest pain diagnosis

A. Basic knowledge of ECG 1. Depolarization and repolarization Single myocardial cell A muscle strip 2. Vector and resultant vector

3. Pacing and conducting system of the heart Sinus node  Internodal tracts  AV node  right bundle branch (RBB) Purkinje fibers Bundle of His anterior fascicle left bundle branch (LBB) Purkinje fibers posterior fascicle

4. Lead system ☆ Limb leads: Standard leads: I, II, III ☆ Limb leads: aVR, aVL, aVF Hexaxial system Hexaxial system Chest leads: V 1, V 2, V 3, V 4, V 5, Chest leads: V 1, V 2, V 3, V 4, V 5, V 6, V 7, V 8, V 9 V 6, V 7, V 8, V 9

B. Normal ECG  P wave  PR interval  QRS complex  ST segment  T wave  QT interval  U wave

1. Measurement of ECG waves and intervals  ECG paper  ECG paper  Measuring heart rate (HR) = 60/R-R (bpm)  Measuring heart rate (HR) = 60/R-R (bpm) regular or irregular rhythm regular or irregular rhythm  Amplitude of waves or segment: P, QRS,  Amplitude of waves or segment: P, QRS, S-T, T, U S-T, T, U  Width or duration of waves: P, QRS, T, U  Width or duration of waves: P, QRS, T, U  Duration of intervals: P-R, Q-T  Duration of intervals: P-R, Q-T  Shape of waves: P, QRS, T  Shape of waves: P, QRS, T

2. Mean QRS axis  normal cardiac axis range from -30  90   significant left deviation: -30  -90   right deviation: 90  180   significant right deviation: 180  -90   significant right deviation: 180  -90  3. Clockwise and counterclockwise rotation 3. Clockwise and counterclockwise rotation  Clockwise rotation  Counterclockwise rotation  Counterclockwise rotation

4. Normal ECG (1) P wave: atrial depolarization Amplitude  0.20 mv Amplitude  0.20 mv Duration  0.11 sec Duration  0.11 sec Positive in I, II, aVF, V4-V6; Positive in I, II, aVF, V4-V6; Negative in aVR Negative in aVR (2) PR interval: the time for intraatrial, AV nodal, and His-Purkinje conduction, AV nodal, and His-Purkinje conduction, Duration: 0.12 ~ 0.20 sec Duration: 0.12 ~ 0.20 sec

(3) QRS complex: ventricular depolarization The width: 0.06  0.10 sec,  0.11 sec. The width: 0.06  0.10 sec,  0.11 sec. From V 1 to V 6, the R waves gets bigger and bigger, the S waves gets smaller and smaller. From V 1 to V 6, the R waves gets bigger and bigger, the S waves gets smaller and smaller. R/S l in V 5 R/S l in V 5 R in V 5 and V 6 < 2.5 mv, R in V 1 < 1.0 mv R in V 5 and V 6 < 2.5 mv, R in V 1 < 1.0 mv R in aVR < 0.5 mv, R in aVR < 0.5 mv, R in aVL < 1.2 mv and R in aVF < 2.0 mv R in aVL < 1.2 mv and R in aVF < 2.0 mv R in I < 1.5 mv R in I < 1.5 mv Q < 0.04 sec in width, < 1/4 R in the same lead. Q < 0.04 sec in width, < 1/4 R in the same lead.

(4) ST segment: it reflects Phase 2 of the action potential. ST elevation < 0.3 mV in V 1 、 V 2; 0.5 in V 3, ST elevation < 0.3 mV in V 1 、 V 2; 0.5 in V 3, < 0.10 mV in V 4  V 6 < 0.10 mV in V 4  V 6 ST depression < 0.05 mV in any leads ST depression < 0.05 mV in any leads (5) T wave: repolarization of ventricles It is upright in all the unipolar leads except It is upright in all the unipolar leads except aVR, and occasionally V 1. aVR, and occasionally V 1. T wave > 1/10 R in the same lead, maybe T wave > 1/10 R in the same lead, maybe < 1.2  1.5 mV in the precordial leads < 1.2  1.5 mV in the precordial leads

(6) QT interval : the duration of depolarization and repolarizaion of ventricles. The normal range is 0.32  0.44 sec. (7) U wave : the wave following the T wave and is usually very small. Its cause is not completely understood. Elevated U wave: low K + in plasma

C. Summary Why ECG could be served for the diagnosis of some diseases? How does ECG work? What is ECG? What is normal ECG? 1. Basic knowledge of ECG(electrocardiogram) Depolarization and repolarization: Vector and resultant vector Pacing and conducting system of the heart Lead system: (Limb leads) I, II, III, aVR, aVL, aVF, (Chest leads) V 1, V 2, V 3, V 4, V 5

2. Normal ECG: P wave, QRS complex, T wave, U wave, PR interval, QT interval, ST segment, U wave, PR interval, QT interval, ST segment, R-R (P-P) R-R (P-P) Mean QRS axis Mean QRS axis Clockwise and counterclockwise rotation Clockwise and counterclockwise rotation Normal value and shape: Amplitude of waves or segment: P, QRS, T, U Amplitude of waves or segment: P, QRS, T, U and S-T and S-T Width or duration of waves: P, QRS, T, U Width or duration of waves: P, QRS, T, U Duration of intervals: P-R, Q-T Duration of intervals: P-R, Q-T Shape of waves: QRS, T Shape of waves: QRS, T Clinical significances of abnormal ECG

TEST in classroom Please translate the following words into Chinese: Please translate the following words into Chinese:

PRACTICE Make an ECG by yourself first Read and measure your ECG with correct way and steps Is your ECG normal or abnormal? Keep your ECG for memory. It is the first time as a doctor to make ECG and diagnosis! Good beginning is the half of success!