I am having excruciating pain under my left shoulder blade which is running down my arm and causing tingling in my hand.

Pinched nerve. Because patients having cardiac problems can have these symptoms, you should have this ruled out. But the most common cause is an irritation of a nerve in the neck by a bone spur or herniation that can cause pain or numbness that runs down the arm into the hand. An MRI can usually show the cause of the problem if it does not resolve. Thank you for the question.