1 Basic knowledge of electrocardiogram心电图基础知识
1)Normal cardiac electrical conduction system (Fig.1-1) 正常心脏电传导系统（图1-1）
Fig.1-1 Cardiac electrical conduction system
图1-1 心脏电传导系统
Cardiac conduction system pathway is composed of the following elements:
a) SAN: Sinoatrialnode
b) AVN: Atrio-ventricularnode
c) His: His bundle
d) LBB: Left bundle branch
e) RBB: Right bundle branch
f) Purkinje fibers
心脏正常传导系统由以下部位构成：
a) 窦房结
b) 房室结
c) 希氏束
d) 左束支
e) 右束支
f) 浦肯野纤维
Normally the cardiac stimulus is generated from the sinoatrial node (SAN), its electrical activity passes the left and right atrium to the atrioventricular node (AVN) and His bundle, then transmitted by the left bundle branch (LBB) and right bundle branch (RBB), finally through the Purkinje fibers conduction to the left and right ventricular cardiomyocytes.
心脏电传导由窦房结发放指令，其电活动通过左、右心房传导至房室结和希氏束，然后通过左束支和右束支传导下传，最后通过浦肯野纤维传导至左、右心室的心肌细胞。
If high-level cardiac pacing failure occurs, a protective pacemaker will appear in the lower tissue. The rates of cardiac pacing in various tissues are as follows:
SAN: 60-100bpm
AVN: 40-60bpm
Ventricle: 20-40bpm
如高级别的心脏起搏丧失，则下级组织将出现保护性起搏。不同组织的起搏频率如下：
窦房结：60～100次/分
房室结：40～60次/分
心室：20～40次/分