Ventricular and Atrial Septal Defect – Blood Vessel and Heart Abnormalities

by John McLachlan, PhD

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    00:00 the ductus arteriosus is closed. Let’s look at our major defects. As we said, the most common of those is the ventricular septal defect marked in this diagram here.

    00:09 It’s most common near the junction with the atrium. Just look back at the previous slide and what we can see is that the intraventricular septum runs all the way up to the atrial junction.

    00:23 Then in the defect, this is the part that’s actually missing. Now, many VSDs are small, and they may not be clinically significant. In fact, some of them will heal spontaneously.

    00:36 So the presence of a VSD is not in itself necessarily life threatening. But you can see that what will happen is that blood will cross the heart from left to right.

    00:47 And babies with a moderate ventricular septal defect or VSD may breathe more quickly because the supply of oxygenated blood is reduced by this process. As a result, they may exhibit per weight gain. They may also be slow to feed, and they may be prone to chest infections and that’s because the blood supply to the lungs is not as rich in oxygen as it would normally be, otherwise. And this fact can cause cyanosis. So the lack of oxygen in the blood can lead some of the membranes to begin to look blue. You may see this in the fingernail beds or in the lips. Let’s look now at the atrial septal defect. In this diagram, you can see in the arrows that blood is crossing from the left atrium into the right atrium.

    01:37 So it’s not making it into the pulmonary circulation at all. Instead, it’s passing on down into the right ventricle and going around the heart in such a way as to avoid the pulmonary circulation. This may be a high level, or as in the diagram on the right-hand side, may be at a lower level. Atrial septal defect is sometimes associated with Trisomy 21 Down syndrome. So if you identify a child suffering from Trisomy 21, this would be a useful thing to look for, clinically. Again, if it’s a minor condition, if it’s a small hole, then it may cause no detectable problems. Indeed, it may not be spotted until the baby begins to walk. At that point, there’s an increase in demands on the heart and in the circulatory system. At this point, a defect like an ASD, an atrial septal defect, may become obvious. Of course, even when it’s identified, it may be decided to defer surgery to correct it to later. Obviously, operating on baby’s hearts and infant’s hearts is difficult because of their very small size and sometimes it’s better to allow the child to grow so that the operation can be carried out to a later stage. Also, there are possibilities for closing the atrial septal defect by catheterization so that open heart surgery is not required.

    About the Lecture

    The lecture Ventricular and Atrial Septal Defect – Blood Vessel and Heart Abnormalities by John McLachlan, PhD is from the course System-Specific Embryology with John McLachlan.

    Author of lecture Ventricular and Atrial Septal Defect – Blood Vessel and Heart Abnormalities

     John McLachlan, PhD

    John McLachlan, PhD

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