Another important reason is that the physical examination items in this era are too simple. In the physical examination that children take at school every year according to national requirements, the most they can do for their heart is to take an electrocardiogram and a chest X-ray. Some schools don’t even arrange an electrocardiogram. In the absence of instrument detection, doctors use a simple stethoscope to try to hear the subtle problems in the heart: well, doctors who can do this are gods.
Besides, the heart diseases that can be diagnosed solely by electrocardiogram and chest X-ray are very limited.
To give the simplest example, the sixteen-year-old girl in bed 12 suffers from atrial septal defect.
This disease can be considered a serious or minor disease. Interestingly, it is a congenital disease, which means it is born with abnormalities from the beginning of embryonic development. The strange thing is that many cases of this congenital disease are diagnosed in adults, making it a common heart malformation disease in adults. What does this mean? It means that it is difficult to detect it without accurate medical detection equipment. To be precise, a cardiac ultrasound is required.
Why can't this disease be detected in time by electrocardiogram and chest X-ray? Let's talk about its pathogenesis.
The atrial septum is like a wall. As the name suggests, it is located between the left atrium and the right atrium. The job of the wall is to block the blood in the left atrium and the blood in the right atrium, so that the blood in these two atria cannot communicate.
The name of atrial septal defect is more vivid, describing the characteristics of this disease: the wall is defective. The defective wall is manifested as either a hole, one, two, or three holes, or a direct defect, with a whole wall missing a piece.
Since the cause of this disease is congenital, we should start with how the atrial septum grows.
When building the atrial septum, you need to build an initial wall first, which is called the primary septum. If there is an abnormal missing block during the construction of the primary septum, the gap left is called the primary foramen. If the primary foramen cannot be filled, it is called a primary foramen atrial septal defect. This is one of the types of atrial septal defect.
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According to the above statement, the primary diaphragm needs to be built completely, so that the disease will not occur. The problem is that the process of building the atrial septum wall is that the baby is in the mother's womb during the fetal period.
There is a big problem with building walls during the fetal period: the oxygen and other nutrients that the baby absorbs during the fetal period are obtained through the placenta, not through its own breathing and lung circulation. Therefore, the right atrium and left atrium of the fetus need to be connected, so that the blood rich in oxygen and other nutrients in the placenta can flow directly into the baby's left atrium and left ventricle, and then go to the entire systemic circulation to nourish the whole body.
So, if we build a wall to separate rooms, we can’t block the entire wall. What should we do?
The original wall was degraded into a hole, which grew later, so it is called a secondary hole.
The secundum foramen is useful to the baby during the fetal period, but it is useless after the baby is born, and it will cause problems if it is left. The human body has prepared to block the hole in advance, so another wall called the secundum diaphragm grows on the original wall. This secundum diaphragm is equivalent to a patch to block the hole. At this time, the secundum foramen has another name, which many mothers have heard of: the famous foramen ovale.
In summary, in order to keep the left atrium and the right atrium connected during the fetal period, the secondary diaphragm and the primary diaphragm are not fused. This allows blood to enter the oval foramen of the right atrium and then pass through the gap between the primary diaphragm and the secondary diaphragm to the left atrium.
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