When you consider how complex the process of prenatal development is, it seems remarkable that healthy babies are born at all. Every now and then, however, babies are born with a rare congenital defect that causes the large vessels in their heart to be connected in ways that are contrary to their normal orientation.
This condition is called Transposition of the Great Vessels (TGV), and it can manifest itself in a few different ways.
The most well-known variant of TGV is Dextro-Transposition of the Great Arteries. In this case, the two main arteries leaving the heart are swapped, causing oxygen-rich blood to return from the lungs without circulating through the body. Babies afflicted with this condition often exhibit cyanosis, or blue-tinted skin, because their hearts pump unoxygenated blood through their bodies.
Another less common variant of TGV is called Levo-Transposition of the Great Arteries. Also known as congenitally-corrected transposition, this condition occurs when the left and right lower chambers of the heart are completely reversed. In these cases, the heart is able to distribute oxygen-rich blood to the rest of the body, but through the wrong ventricles. Because each ventricle is designed to operate at different pressures, Levo-Transposition can cause heart fatigue and shortness of breath in the long term. It is typically not as immediately obvious or dangerous as Dextro-Transposition, though, and people can often lead normal lives without having Levo-Transposition surgically corrected.
You can see one example of TGV in the image above. Here, the aorta (top artery in blue) and pulmonary trunk (top vessel in red) are reversed. This allows unoxygenated blood to be pumped back out through the aorta before it can be refreshed with oxygen in the lungs.
This type of illustration is designed to help patients better understand conditions that might otherwise be difficult for physicians to explain. To see more of these clinical illustrations, check out my portfolio page here!