For most MFM and OB sonographers there are just certain parts of a baby that we love to image. Some people love faces, some love the spine, for me.... it's the heart. Specifically the Aortic Arch. My love of the Aortic Arch is well known in my practice and my MFMs give me a little grief from time to time about it.
Now, I didn't always love the heart but it has grown on me over the years. The heart itself felt overwhelming in the beginning. So many parts and things that could go wrong. It felt so overwhelming that I didn't even know where to start or how to learn. I started my ultrasound career as a general sonographer in a hospital setting. I moved into an outpatient center after a few years and even though I performed OB/Gyn studies we were only required to document the four chamber heart (4CH) view. We didn't perform a lot of OB exams so it was hard to gain experience and feel confident in my practice of OB exams. What also didn't help was that the Radiology group I worked for was more geared towards General sonography and Vascular. I had no training and the sonographers I worked with at that time also didn't care for OB so my learning was pretty limited. Even our CMEs were directed towards General and Vascular. What changed all this you ask? My 1st pregnancy did! I was deemed high risk in that pregnancy and that is when the world of MFM was opened up to me. How had I not realized how amazing OB could be? That was when I decided to change my path and focus on Ob/Gyn and subsequently find my way into MFM.
Anyways, back to the heart! The Aortic Arch is an intricate part of the fetal heart. The way I explain it to patients is that the 4CH part of the heart and overall front views of the heart tell me how the heart is made-more like the plumbing of the organ. But the arches tell me how the baby moves their blood in and out of the heart in-utero.
According to Radiopeadia, the Aortic Arch is the direct continuation of the Ascending Aorta. There can be normal variants of anatomy and a wide range of abnormalities located within the arch. These include congenital anomalies and traumatic injury.
The Aortic Arch in its entirety is seen sagittally. It is normally referred to as having a "candy cane" appearance. There are 3 vessels that extend off the arch. They are:
Brachiocephalic (or Innominate) which then turns into the Right Subclavian and the Right Common Carotid
Left Common Carotid
I always remembered the nemonic 2 left feet to remember that there are 2 left sided vessels.
There are 3 areas of the Aortic Arch. The Ascending which is the the part of the Aorta from the Left Ventricle before the Arch. The Transverse Aortic Arch which includes the Isthmus. Then the Descending Aorta.
The most common normal variant of the Aortic Arch is a Bovine Arch. According to Radiopaedia, a Bovine Arch occurs in about 15% of the population and is more common in people of African American descent.
A Bovine Arch occurs when the 1st vessel to extend off the arch, the Brachiocephalic, is joined by the Left Common Carotid Artery. This creates a common origin. So instead of 3 separate vessels coming off the Aorta, you would only see 2.
What's funny about this is that Bovines (or Cattle) actually have a common single Brachicephalic trunk. That vessel then trifurcates into the subclavian arteries and a single bicarotid trunk. This single vessel is very rare in humans. I personally have never seen it and I have been looking for it for years... believe me! So if anyone ever see this please send me the picture! Ok?
In the animal world there are animals that normally have 2 branches off the Aorta. It has been noted that cats have this variant. Maybe I'll start calling it a feline arch and see what my Doctor thinks of that! LOL
If we really wanted to get specific we would describe the branch itself. "Common origin of the Brachiocephalic Artery and Left Common Carotid Artery"
When we see a Bovine Arch we think, just a normal variant right? According to the Journal of the American Heart Association, "A Bovine Aortic Arch is associated with LEFT hemispheric laterality of cardioembolic stroke". Left sided hemispheric strokes are more frequent and have a worse outcome than right sided strokes.
So I hope as you continue on in your practice and love of fetal hearts you find that piece of anatomy that just speaks to you! And as you watch the fetal Aortic Arch, hopefully you will think back to this blog and think-- Hey! I know what that is!
Information from: https://radiopaedia.org/articles/aortic-arch?lang=us
Image of Normal 3 vessel Aortic Arch taken from: https://obgynkey.com/coarctation-of-the-aorta-and-interrupted-aortic-arch/
Image of Bovine arch taken from: