If you have only ever experienced the blackouts when standing up quickly and you have low blood pressure then the two will almost certainly be linked. If you are telling this to your AME then make sure you stress that you have low blood pressure which is probably the cause.
Low blood pressure is good in most cases as it means you are fit and healthy and your heart doesnt need to work as hard, however it can be bad and reveal underlying health problems. I would suggest checking your blood pressure as it has probably gone very low which would cause most to blackout when standing up. Maybe speak to your GP about ways to increase your BP before going to see your AME. Many things can cause it....