Prinzmetal is a spasm of a vessel and the appropriate test would be to provoke an episode in the cath lab with an injection of ergotamine.
There is some evidence low levels of intracellular magnesium and therapeutic response to intravenous magnesium have led to the suggestion that it may be involved. Also, low plasma levels of vitamin E in patients with active variant angina and improvement in symptoms when vitamin E is used supplementary to calcium channel blockers has been observed.
Treatment for coronary artery spasm is with calcium channel blockers (nifedipine, diltiazem, verapamil, etc) and nitrates (nitroglycerine).
Hope this helps, and thanks for sharing. If you have any further questions or comments you are welcome to respond. Take care, and I wish you well going forward.