I have a SADS arrhythmia (CPVT) as well as dysautonomia. In fact, most people with a SADS arrhythmia have some level of dysautonomia. It's not uncommon for dysautonomia to present as a symptom of another condition, but it can also be a condition by itself.
The reason there are so many possible symptoms in dysautonomia is because the autonomic nervous system regulates so many of the body's functions. Nearly every part of the body that is controlled automatically (without thought), is controlled by the autonomic nervous system. Your ANS controls when you blink, when you breath, when your blood vessels constrict or dilate, how your body responds to its own adrenaline, etc.
Doctors have grouped the most commonly occurring symptoms together, and given them names like POTS, NCS, NMS, PAF, SDS, IST, HS, FD, etc. Not everyone can fit in one of these boxes though, and that's why many people refer to their disorder simply as autonomic dysfunction.
Although most forms of autonomic dysfunction are benign, there are rare progressive forms as well. Shy-Drager Syndrome, and some forms of Familiar Dysautonomia come to mind.
Theoretically, even a benign form of dysautonomia could be fatal if the unconscious individual was held in a vertical position. Since fainting normally results in a horizontal position, the autonomic system doesn't have to work against gravity to force blood back into the brain.
Like Kessie, I also have a SADS arrhythmia. I have Long QT Syndrome, and severe dysautonomia. Like you, I also have benign PVC's. I agree, dysautonomia can absolutely be connected with abnormal heart rhythms.
I'm curious, have you ever had an EP study? It is possible that your SVT could be treated by catheter ablation.
My dysautonomia causes me to have nearly constant low blood pressure. My heart rate varies from slow to fast, and my respiration becomes almost non-existent. Some of my other symptoms include: nausea, dizziness, vomiting, fainting seizures, sweating, disorientation, headaches, darkened vision, fatigue, etc.
You seem to be very knowledgeable in this subject. How is dysautonomia different from conversion disorder? I have a niece struggling with undiagnosed symptoms.
Unfortunately, I'm not entirely sure how to answer your question. I don't know much about Conversation Disorder. I'm sure there are other communities on Medhelp that may provide more information on the subject though. Perhaps even one of our own community members will have further input.
I hope your niece will feel better soon. Do you believe she may have some type of Dysautonomia?