المعروف أن عضلات الاذينين صغيرة جدا اذا ما قورنت بعضلات البطينين و لذلك فان التيار الكهربائي المصاحب لانقباض الاذينين سيكون صغيرا و
It is known that the atrial muscles are very small compared to the ventricular muscles, and therefore the electrical current accompanying atrial contraction will be small and is symbolized on the ECG by the symbol (P wave), while ventricular contraction is symbolized by the symbol (QRS complex), and after it, ventricular relaxation is symbolized by the symbol (T wave), as the cardiac cycle begins with atrial contraction, then their relaxation, then ventricular contraction, then their relaxation, and all of this is recorded as waves on the ECG paper...
In order of events:
1. Atrial contraction (P wave).
2. Then their relaxation (-) – and here atrial relaxation is not recorded because it occurs at the same time as ventricular contraction, and thus ventricular contraction prevents the recording of atrial relaxation.
3. Then ventricular contraction (QRS complex).
4. Then their relaxation (T wave).
Regarding the QRS complex, the first downward deflection from the straight line is called (Q wave) and the deflection that follows it upward is called (R wave) and it may or may not be preceded by (Q wave), then it is followed by another downward deflection called (S wave) and it also may or may not be preceded by a Q wave... meaning that it is not necessary for ventricular contraction to be represented by the entire (QRS complex).
And any change in these images reveals a problem that may be in the heart rate or as a result of an artery blockage or something else, but the most commonly used and clearest images are (lead II) and (avR), and one of them is used to monitor the patient's condition in intensive care units, although the most commonly used is ((lead II.
Summary:
There are 10 electrodes - electrodes - placed on the chest, legs, and arms.... They produce 12 images (leads) and they are as follows:
(Lead I, lead II, lead III, aVR, aVL , aVF, V1,V2,V3,V4,V5,V6).
And in each of these images we find some deflections that symbolize the cardiac cycle:
Atrial contraction: (P wave).
Their relaxation: (-).
Ventricular contraction: (QRS complex).
Their relaxation: (T wave)...
Important rule:
If the direction of the electrical current in the heart is in the same direction as the directed electrode (camera), the result is a negative deflection (downward) on the ECG paper, and vice versa, if the direction of the current is opposite to the direction of the camera, the result is a positive deflection (upward) on the ECG paper, and if the direction of the current has no relation to the direction of the camera, then the signal (deflection) can be of any shape.
And therefore we find that most deflections of (lead II) are positive (upward) because the directed electrode (camera) views opposite to the direction of the current, while the deflections of (avR) are downward because the directed camera views in the direction of the current.
Remember:
Always remember that by the end of this article, you will say how easy it is to read an ECG!!
And so that you do not get lost from the topic, we talked about:
1. The electrical activity of the heart and how the heart beats.
2 . And the ECG machine and how to perform an ECG, and its images.
3 . And we will now address the topic of what we will read on the ECG paper.
Third: What will we read on the ECG paper:
