Some people find out through testing they have definite heart disorder, or vascular disorder, and are helped with medication, but when
test after
test cannot determine any specific cause for the blood pressure changes, or tachycardia, or weakness, etc. etc., doctors end up trying drug after drug, to find something that will help, but stop looking for the source of the system failure.
Neurotransmitters can be altered or affected by so many things.