1.P Wave
The electrical excitement of the normal heart starts from the Sinus node. Because the Sinus node is located at the junction of the right atrium and the upper vena cava, the excitement of the sinus node is transmitted to the right atrium first, through the room bundle to the left atrium, and the P waves on the electrocardiogram are formed. P waves represent the excitement of the atrium, the first half of the right atrium is excited, and the latter part represents the excitement of the left atrium. P wave time is 0.12 seconds, height is 0.25mv. When the atrium expands, the P waves can be expressed as high or bimodal p waves in the two chambers.
2.PR Room
The excitement along the anterior and posterior junction beams conduction into the atrioventricular junction. Because the atrioventricular knot conduction speed slowly, formed the ECG on the PR section, also known as the PR interval. The normal PR room period in 0.12~0.20 seconds. When the conduction of the atrium to the ventricle is blocked, the duration of the PR interval is prolonged or the ventricular wave disappears after the P waves.
3.QRS Wave Group
Excited downward by bundle bundle, left and right bundle branches synchronized with the left and right ventricle formation of QRS wave group. The QRS group represents the ventricular removal pole and the excited time is less than 0.11 seconds. When there is a conduction block of the left and right branches of the heart, enlargement of the ventricular or hypertrophy, the QRS wave group increases the width, deformation and prolonged period.
4.J Point
The intersection of the St segment begins with the QRS wave. The total removal of ventricular myocytes was extremely complete.
5.ST segment
The ventricular muscles were completely removed from the pole and the repolarization had not yet begun for a period of time. At this time, the ventricular muscles in each part are in the polar state, and there is no potential difference between the cells. Therefore, the ST segment should be on the equipotential line under normal circumstances. When the myocardial ischemia or necrosis in a part of the myocardium, the ventricular in the removal of the extreme after the existence of potential difference, at this time the expression of the electrocardiogram on the St segment offset.
6.T Wave
The T-wave then represents the repolarization of the ventricle. The T wave should be the same as the QRS main wave in the upward conduction of the QRS wave. The change of T wave in electrocardiogram is influenced by many factors. For example, myocardial ischemia can be characterized by a flat t-wave inversion. The high blood potassium, acute myocardial infarction, and so on, can be seen in T-waves.
7.U Wave
The U wave is visible after the T wave in some guides, which is considered to be related to the repolarization of the ventricle.
8.QT Room
Represents the time of the ventricle from the polar to the repolarization. The normal QT interval is 0.44 seconds. Due to the effect of QT interval on heart rate, the concept of corrected QT interval (QTC) was introduced. One calculation method is QTc=QT/√ RR. The prolongation of QT intervals is often associated with the occurrence of malignant arrhythmia.