It may not seem like you've had many tests, but the ones you have had are apparently quite conclusive. The gastric empty test obviously confirmed your gastroparesis...tell-tale sign of autonomic dysfunction/neuropathy.

Your heart rate being abnormal had to have come from at least an EKG or holter test...but it must have showed something to make the doctor believe that together with the GI test that you must have an autonomic neuropathy.

Yes, some are diagnosed by a neurologist, but when it comes to autonomic neuropathy (vs peripheral) a GI or even a cardiologist can diagnose it (since it involves the GI tract and cardiac function). Actually, it's quite common for a cardiologist to be the first to pick up on the dysfunction.

If you are not comfortable with the diagnosis, then ask for a autonomic battery to be done (by a neurologist). It would include a holter test, 24 BP, tilt table, QSART and/or thermoregulatory sweat test, and possibly even a skin biopsy for autonomic fiber study.

It really all depends on what your symptoms are as for who does the testing and diagnosing. Obviously you went to a GI for some stomach problems, and he found the answer...gastroparesis. Most with gastroparesis, also have other autonomic dysfunction, so don't be surprised if other testing proves positive as well.

Hope this helps.