I would strongly recommend you speak to your neurologist about this lesion because otherwise you can become very scared by what you read. Below I will describe this lesion, but it is different for everyone and if you aren't having problems from it, then you are doing well and don't need to consider all the possibilities of what could have happened.
Ventral = front-side (as opposed to dorsal) medullary (in the medulla, which is the lowest part of the brainstem).
All the nerves from the brain go through a very small area called the brainstem and cranial nerves 9, 10, 11 and 12 start there as well (controlling the tongue, some neck muscles, your gag reflex and can impact speech ..., basically the lower parts of your head/neck).
60% of people start out with a spibnal cord syndrome (like tingling or weakness or the MS "hug"). 30% start out with optic neuritis and 10% start out with brainstem syndromes, like vertigo (spinning sensation), eye movement problems, balance issues etc.).
So is this atypical? No.
Should you be concerned? Any lesion is concerning, but especially in the brainstem and spinal cord because all the nerves are packed so tightly (as opposed to in the brain, where you may not notice lesions because there may be no to very few clinical outward signs).
Is there a connection between this type of lesion and cardiac issues?