The events that cause vasovagal syncope, vasodepressor syncope, or neurocardiogenic syncope are actually very similar to what happens in a PP KO.
The decrease in heart rate, or rapid drop in blood pressure to the brain can cause unconsciousness. In the case of a person with VVS this can be cause by anxiety. Standing rapidly after sitting can also cause it when the blood has had time to pool in the legs, or by standing too long and locking the knees. After fainting the persons face becomes flush and eyes can become dilated as the blood rushes back to the head. Ever seen a person after a PP KO, red face and eyes are dilated.
The 2 main nerves involved in a PP KO are the 9th (IX) and 10th (X) cranial nerves.
The 9th cranial nerve (also called the Glossopharyngeal Nerve) has a small branch that extends into the Carotid Sinus. This small branch is called the Carotid Sinus Nerve or Hering’s Nerve. The carotid sinus nerve connects to and controls the carotid baroreceptors, which regulates (raises or lowers) the blood pressure to the head.
The Vagus Nerve or 10th cranial nerve’s parasympathetic motor fibers control heart, lungs, and abdominal viscera and are involved in regulation of heart rate, breathing, and digestive system activity. The vagus nerve also regulates the aortic baroreceptors (the body’s blood pressure) in much the same way as the Hering’s nerve regulates the carotid baroreceptors.
In my conclusion, if you do suffer from VVS it could be extremely dangerous to have a PP KO performed on you. A normal person, with a normal functioning Vagus nerve, will have a normal blood pressure in the torso. After the PP KO the Hering’s nerve has to correct the drop in blood pressure to the head which it can easily do because the BP in the torso in normal. In your case with VVS the Vagus nerve (not working correctly) drops the BP in the torso allowing the blood the pool in the legs. If you are KO’ed (under these circumstances) the blood has to return all the way from the legs.
I apologize if any of what I have stated is incorrect or if I have drawn any incorrect conclusions. I am combining what I know of your disorder with what I know of PP KO’s. If some knows otherwise please correct me.
Did you have the tilt-table test done?