Dear Sir/ Madam
A pain radiating to left arm, dizziness
and passing out definitely suggest something important. Although your cardiologist has not found anything, a lot depends upon his degree of suspicion and how extended his work-up was. After the possibility of a cardiac (heart related) condition, possibility of a cervical spine disorder
may also be considered which can have all 3 symptoms.
First seek a cardiologist
review and if everything fine, seek a spine specialist opinion.
Hope this helps.