Hi Jools,
Based on what you have said I would not rush into an angiogram - yes, I have had one recently.
I think there is enough uncertainty in your diagnosis to ask for less invasive testing first so that you can be sure the angiogram is required. However what that testing would be I'm not sure.
From the patient's viewpoint the angiogram is quite easy to undertake - fear and stress (initially) are the main obstacles for most. Once the valium hits the empty stomach you are only half awake

and concentrating at all is a feat. There is no pain, and almost no discomfort. The cardio talked me through the whole procedure as I watched my heart on the x-ray monitor - this seems to be normal.
I think it's important to get the best possible cardiologist (I made a mistake there) and to discuss what their strategy will if they find such and such (eg partial blockages, valve defects etc.). For this you need to read up a bit on what they can and might do.
For the risks you can look at the link below - there are various risks for the various possible problems (this is for Queensland, Australia where I live - the procedures are the same.)
Look here:
[url]http://www.health.qld.gov.au/informedconsent/ConsentForms/shared/shared_file_06.pdf[/url]
Hope this has helped.
Beefsteak