I have had similar issues in recent years and been checked for them with my Cardiologist. And i mean...extensively! 3 Trips to the ER will do that. Definitely check with a cardiologist for a full work up, just for the peace of mind. I was completely clear after stress tests, carotid dopplers, ekg's, etc. And i get rechecked at least once a year. it is scary regardless. At the same time, don't panic.

My cardiologist chalked mine up to a stomach spasm or possible cartilage tearing in the pectoral area. I also have mild Hashimoto's thyroiditis which can cause this type of pain. It can also be genetic. Ask your parents if possible if they have experienced it.

But, now that i have developed the SFN, I wonder if that could play into it in some way.

I have also heard that magnesium deficiency (among other vitamins) can cause a lot of these types of symptoms. I added cocoa powder to my diet in my protein shakes to get some more magnesium in my diet.