(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
正常心电图
心房、心室肥大
T波：反映心室晚期复极过程中的 电位和时间改变。
U波：一般认为是心肌传导纤维的 复极所造成，也有人认为是心室的 后电位。
Normal ECG
(1) P wave: atrial depolarization l Amplitude 0.20 mv l Duration 0.11 sec l Positive in I, II, aVF, V4-V6;
Atrial Enlargement and Ventricular Hypertrophy
(1) Left Atrial Enlargement
Lead II Duration of P wave ≥0.12 sec. ; P wave become bifid (P "mitrale"); The distance of two peak ≥ 0.04sec. Lead V1
l The width: 0.060.10 sec, 0.11 sec. l From V1 to V6, the R waves gets bigger and bigger, the S
waves gets smaller and smaller. l R/S < l in V1, but R/S > l in V5 l R in V5 and V6 < 2.5 mv, R in V1 < 1.0 mv l R in aVR < 0.5 mv, l R in aVL < 1.2 mv and R in aVF < 2.0 mv l R in I < 1.5 mv l Q < 0.04 sec in width, < 1/4 R in the same lead.
P wave become biphasic; Ptfv1 - 0.04 mm·sec
Right Atrial Enlargement
Lead II P wave is peaked (P "pulmonale"); Amplitude of P wave ≥0.25 mV in limb
心内科 -典型心电图诊断
正常时，每次心动周期在心电图上都可以出现P波、QRS波群、 T波和U波、P-R段、S-T段和T-P段，P-R间期和Q-T间期及J点
心电图成份的组成及各波段的测量
心电图测量
QRS波群的命名RRsFra bibliotekqRs
RS
rS
rSr’
qR
QR
Qr
QS
R
rsR’
平均心电轴估测方法示意图
图中箭头示QRS主波方向
正常心电图
P波：反映左、右心房去极化过程 中的电位和时间变化。
P-R段：反映兴奋通过房室交界区， 因其传导非常缓慢，形成的电位变 化也很微弱，一般记录不出来而成 等电位线。
QRS波群：反映左、右心室去极化 过程中的电位和时间变化。
S-T段：表示心室去极刚结束后尚处 于缓慢复极的一段短暂时间，即代 表心室早期复极的电位和时间变化。
(5) T wave: repolarization of ventricles
It is upright in all the unipolar leads except
aVR, and occasionally V1. T wave > 1/10 R in the same lead, maybe
Negative in aVR (2) PR interval: the time for intraatrial,
AV nodal, and His-Purkinje conduction, Duration: 0.12 ~ 0.20 sec
(3) QRS complex: ventricular depolarization
< 1.21.5 mV in the precordial leads
(6) QT interval: the duration of depolarization and repolarizaion of ventricles. The normal range is 0.320.44 sec.
Rv5 or Rv6 > 2.5 mV; RI > 1.5mV; RaVL > 1.2mV; RaVF > 2.0 mV; RI + SIII > 2.5 mV;
B. Left axis deviation
4.0mV (male);
C. ST depression and T inversion in V5-6.
Right Ventricular Hypertrophy
A. Increased voltage (adults over 30)
R/S ratio in V1 > 1.0; R/S ratio in V5 or V6 ≤
1.0; R/q or R/S ratio in
aVR≥1;
R(sevVe1r+e>1S.2mV5V); >1.05mV RaVR>0.5mV;
正常人胸导联R波和S波振幅变化规律示意图
(4) ST segment: it reflects Phase 2 of the action potential.
l ST elevation < 0.3 mV in V1、V2; 0.5 in V3, < 0.10 mV in V4 V6
l ST depression < 0.05 mV in any leads
leads.
Biatrial Enlargement
Lead II
P wave duration and amplitude both increased.
Left Ventricular Hypertrophy
A. Increased voltage
SV1 + R V5 >3.5mV (female),