Do you mind if I ask how you were diagnosed with autonomic dysfunction? The reason I ask is because I'm wondering how much of a workup you have had since that will help your doctors guide treatment. I haven't heard of BB being prescribed as a sole treatment for dysautonomia, so any extra info you have might help.
I have both POTS and cardiac problems which we are trying to get to the bottom of. My understanding is that they two are separate workups and I must close the loop on both.
BBs are known for their ability to slow pulse and cause heart rhythm abnormalities. I'm not a doctor, but inclined to think most of those side effects you are complaining about above are related to the BB. BBs can also cause some changes in BP which can lead to lightheadedness, fatigue, and syncope. You don't say what your BP was in all this, so I'm wondering if it may have gotten too low - these sound like the same effects which are why they won't let me go on a BB despite everything else indicating I should - my BP of 100/70 contraindicates for even a pediatric dose.
If you haven't been diagnosed or treated by a Neuro familiar with dysutonomia, I would try going there. Definitely keep your cardiologist given the number of risk factors you have and the fact it sounds like you still need ongoing workup, but neurology approaches dysautonomia differently. You may be like me and have two separate things going on.
Things will get better, I'm hoping it all comes together for you soon.
You may be interested in this article...
Cardiac Autonomic Dysfunction
Effects From Particulate Air Pollution and Protection by Dietary Methyl Nutrients and Metabolic Polymorphisms
It seems to link the MTHFR methylation errors to Autonomic Dysfunction. MTHFR errors apparently prevent you from utilizing the cheap synthetic vitamins...folic acid and cyano-cobalamin (B12) effectively. You basically end up with a cellular deficiency even though your serum levels look fine. If you find the correct Dr to help you, they will probably check to make sure your other levels aren't off, and then recommend that you use natural or bio-available Folate (NOT folic acid) and B12 in the methylated forms to counteract your low MTHFR enzyme level.
I ran my DNA and a methylation profile using 23and me.com and Genetic Genie....and found that I carry multiple MTHFR mutations/metabolic polymorphisms.
I think its certainly something worth discussing with our physicians!