Tuesday, February 5, 2008

Development of the Heart

A special thanks to Josie, the mother of a little girl who was has the CHD known as Transposition of the Greater Arteries (TGA), for today's post!

When you stop to think about the process of fetal development, really think about what is happening every day, it's absolutely breath-taking. The heart is one of the very first organs to form, in fact, it begins to beat often before the mother even knows that she's pregnant, within 21 days of conception. Congenital heart defects thus occur in the first days and weeks of existence; by the time the heart begins beating, most structural anomalies already exist. Depending on the particular defect, that may only be the beginning.

Although the structures of the heart exist from the earliest days, the heart itself continues normal development throughout the pregnancy. The flow of blood through the heart furthers growth and development of the various structures. When there is a structural anomaly, the blood may follow an unusual path through the heart and thus exacerbate the defect. Other defects result not from structural problems, like our daughter's, but rather from problems with the valves in between each section of the heart. Valves are critical to normal cardiac functioning because they prevent the backwards flow of blood as the heart contracts to pump blood to the body and the lungs. In order to function properly and efficiently, the flaps must be thin and pliable and should open completely and close completely. When they don't work, either because they are too small and restrict the flow of blood through the valves, or because they are weak and leaky, the development of the fetal heart may be seriously impacted. Problematic valves may prevent entire chambers of the heart from growing and developing.

But I digress. The point of this post was to explain that congenital heart abnormalities exist from the earliest days of the pregnancy. And no one knows why. No one knows what triggers the incorrect formation or when exactly development goes awry. Sometimes, although very rarely, there is a genetic component. The vast majority of congenital heart defects have an unknown cause and therefore we don't know how to prevent them. Seriously, when you stop to think about it, a normal heart is really quite amazing!

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