A colleague of mine at work showed me a very interesting echo that was done the day before. (I currently work part-time and an adult lab). The apical views showed what appeared to be a membrane in the right atrium that looked just like a cor Triatriatum. Angulating a little differently, this membrane looked circular and was located in the superior, left medial portion of the right atrium. I wish I had video of this, but I do not, technically, know how to do this.
This is a pediatric lab also, some of us do pediatric echos, and the general consensus was that this was probably a cor triatriatum, but in the right atrium.
How could this be?
Cor triatriatum is generally a defect of the left atrium and is the result of the incomplete absorption of the common pulmonary vein into the left atrium in vivo. The pulmonary vein, in vivo, grows from the lung buds towards a morphologic left atrium, and then splits into 4 veins that complete circulation from the lungs to the left atrium.
Total anomalous pulmonary veins typically happen when there is juxtaposition of the atria, that is, the atria are switched. The left atrium is attached to the right ventricle, and the right atrium is attached to the left ventricle.
Remember, that the common pulmonary vein will attempt to attach to the morphologic left atrium, and the vena cava will attempt to attach to a morphologic right atrium. If the atria are “switched”, then the pulmonary veins may end up draining into a morphologic left atrium attached to the right ventricle.
Using the same scenario, if the atria are switched, then the caval veins will attempt to attach to the morphologic right atrium (connected to the left ventricle). This is what leads to a “persistent left superior vena cava”.
A bubble study was done while imaging in the 4-chamber apical view, with the “membrane” showing as a circular structure in the right atrium. The bubbles immediately infiltrated the right atrium, bypassing the circular membrane and infusing the entire right heart, with no infiltration of the left heart. Further, no bubbles infiltrated inside the “membrane”.
I concluded that this was an aneurismal coronary sinus. Here is my logic:
- If this were some type of cor triatriatum, then the bubbles would have infiltrated the membrane, and would have had a difficult time passing the membrane into the right ventricle.
- If this were a partial anomalous pulmonary vein, the bubbles probably would have showed up in the left side of the heart.
- If this were a juxtaposition of the atria, then bubbles probably would have showed up on the left side of the heart due to either anomalous pulmonary venous return or a persistent vena cava.
- At least one of the vena cava were attached to the right atrium. Bubbles were injected into the IV on the arm, the bubbles immediately showed up in the right atrium which means that, at least, the superior vena cava attached to the right atrium.
- No bubbles showed up on the left side of the heart, meaning there was no connection between the right and left sides of the heart.
I suggested that a bubble study should have also been done in the subcoastal view. It is possible to image both the superior and inferior vena cava with just slight angulation. If one had seen bubbles in both caval veins, this would certainly R/O persistent left superior vena cava.
So, I put this out to my followers. If this is not an aneurismal coronary sinus, then what could it be?