Image 2
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Image 2
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Image 2 is the RAO of the same vessel. It is an anomalous left coronary artery.
It passes to the left between the aorta and pulmonary artery. The RAO shows
this best, as it clearly does not got back enough to be retro-aortic nor anteriorly
enough to wind around the anterior face of the right ventricular outflow tract.
The arrowed vessel allows the diagnosis to be made in the LAO view. It is an
early branch , going straight downwards into the septum. In fact it goes into
the crista superventicularis first before ending up in the upper septum, and
it is usually called the cristal artery. With the retroaortic and pre RVOT pathways,
there is never a branch going downwards so early.
This downward vessel has the same embryonic path as the right superior septal perforator, which you will find in the downloadable quiz. It marks the anomalous vessel as "transcristal", the usual path for this anomaly. Beware that there is a rarer variant, so called "interarterial anomalous LCA" which is higher and does not have a cristal branch: it is prone to compression whereas the transcristal path is, in my experience, benign.