Children with left heart hypoplasia mean that the left ventricle is poorly developed. The cause of poor development is generally attributed to problems with the inlet mitral valve and outlet aortic valve of the left ventricle, which may be dysplasia or direct atresia. The left ventricular cavity is smaller, and the chain reaction is that the ascending aorta becomes smaller, changing from a large blood vessel to a small blood vessel.
We know that the left ventricle is very important to the human body, and the blood pumped out must support systemic circulation. The small left ventricle and the small exiting aorta reduce the blood flow pumped to the systemic circulation, causing ischemia and hypoxia in children. In order to maintain sufficient blood flow to maintain systemic circulation, the child's heart can only work faster, leading to and aggravating heart failure. As a result, a series of clinical symptoms mentioned above appeared.
To sum up, several links of the left heart system all have problems under the influence of each other during the development process, so it is called hypoplastic left heart syndrome.
Why don't this child's current symptoms seem serious?
"He was shunted due to multiple atrial septal defects and patent ductus arteriosus." Xie Wanying added some of her own speculations.
We talked about the situation of the child when it is in the mother's belly in the chapter on the interatrial septum. The cardiac and circulatory system during the fetal period is different from that after birth. The same is true for this disease. Only after the child is born can he breathe on his own, and finally realize the serious consequences of this heart abnormality, can the symptoms of the disease gradually appear.
It seems that the best way to prevent the child from ischemia and hypoxia is to theoretically return the child's cardiac and circulatory system to the condition it had during the fetal period. The atrial septal defect was large, just like the unclosed wall during fetal period for shunting. At the same time, the ductus arteriosus during fetal period is not closed, allowing blood from the pulmonary artery to flow to the aorta to support systemic circulation as it did during fetal period.
As classmate Xie said, this child's heart has grown like this. No wonder the symptoms are mild.
Can this situation continue?
The answer is impossible. First of all, according to normal conditions, the ductus arteriosus begins to functionally close within hours to days after birth, and anatomically closes after one or two months, which is the same as the closure of the foramen ovale. Even if it is not closed, if this situation lasts for a long time——
"It's definitely not possible if we don't do the surgery quickly. If we delay it any longer, I'm afraid it will turn into pulmonary hypertension. When it comes to pulmonary hypertension, there's no possibility of Fontan surgery." Xie Wanying said.
This means that according to the above principles, whether it is patent ductus arteriosus or atrial septal defect providing shunt support, it only solves the problem of insufficient blood flow in part of the systemic circulation. It cannot prevent the existence of arterial mixed blood, and the mixed blood is pumped out into the systemic circulation. It also causes hypoxia in the body. Fontan surgery involves a total cavopulmonary anastomosis, which directly connects the superior and inferior vena cava to the pulmonary artery. This allows only arterial blood with high oxygen content in the heart chambers and avoids mixing of arterial blood. The pumped blood only enters the systemic circulation as arterial blood, which can greatly improve the body's hypoxia.
The prerequisite for Fontan surgery is good pulmonary circulation and no pulmonary hypertension. What to do? This involves the Norwood operation, which is the first choice for treating left heart hypoplasia. The entire atrial septal defect is simply cut away to expand the communication between the rooms.
Then cut the main pulmonary artery at the bifurcation of the left and right pulmonary arteries, connect the side of the main pulmonary artery to the side of the aorta and enlarge the aorta.
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