I. P-wave
Time limit: ＜0.12 sec
Amplitude: ＜0.25mV (limb leads)
<0.2mV (chest leads)
Direction: sinus rhythm
Ⅰ, Ⅱ, avF, V4-V6 leads upright
avR leads inverted
Other leads upright, inverted, or biphasic
II. P-R interval
PR normal value 0.12-0.20 sec
represents the atrioventricular conduction time
The older the age, the slower the heart rate and the longer the P-R interval
The younger the age, the faster the heart rate, the shorter the P-R interval
QRS wave group
1.Time limit: 0.06 ~ 0.10 seconds, <0.12 seconds
2, waveform: according to the direction of the main wave and the presence of Q (q) wave
(1) I, II, V4 ~ V6 leads main wave: up; avR, V1 leads main wave: down
(2) V1, V2 leads should not have Q (q) waves; avR, Ⅲ, avL leads can have Q or q waves
(3) Ⅰ, Ⅱ, avF, V4 ~ V6 leads should not have Q waves (can have q waves)
(4) V1 ~ V6 leads R wave gradually become larger, S wave gradually become smaller, R / S from small to large
(5) Q wave less than 0.04 seconds, amplitude <1/4 with the lead R wave
3.Voltage.
(1) at least one limb lead QRS wave group voltage and ≥ 0.5mV; at least one thoracic lead QRS wave group voltage and ≥ 0.8mV
(2) RavL <1.2mV, RavR <0.5mV, RavF <2.0mV, RI <1.5mV, Rv1 <1.0mV, Rv5 <2.5mv
(3) Rv5+Sv1＜4.0mV (male); Rv5+Sv1＜3.5 (female), Rv1+Sv5＜1.2mV
4, R peak time (ventricular wall excitation time).
Concept: the spacing from the beginning of QRS to the vertical line of the top of R wave
Time limit: ≤ 0.04s (in V1, V2); ≤ 0.05s (in V5, V6)
Fourth, the ST segment
The ST segment is generally located on the isoelectric line without significant offset, and the normal range of offset.
1, all leads ST segment downshift ≤ 0.05mV
2, all limb leads and V4-V6 leads ST elevation ≤ 0.1mV
3, ST-segment elevation in leads V1-V2 ≤ 0.3mV; ST-segment elevation in lead V3 ≤ 0.5mV
V. T wave
Morphology: two asymmetric branches, ascending branch is gentle, descending branch is steep
Direction: I, II, V3-V6 leads upright, avR inverted, the rest can be upright, flat, inverted, biphasic
Amplitude: QRS wave group upright leads, T-wave voltage should exceed one-tenth of the R-wave in the same lead
VI. QT interval
Normal range: about 0.32-0.44 seconds
Corrected Q-T interval (QTc) = QT / RR1/2
Clinical significance: represents the sum of ventricular depolarization and repolarization time
VII. U wave
1. Post-ventricular depolarization potential, ventricular secondary potential, mechanism unclear
2, abnormal U wave for ventricular repolarization abnormal, normal people can have no U wave
3, if there should be lower small, generally V3 ~ V4 leads more obvious, voltage, time should be significantly smaller than the T wave, U wave must be upright
4.Significantly increased, see the blood potassium is too low