This sounds weird but mine are just exactly like a heart attack. I have had them occasionally for years. No physical reason for them as I have had a heart cath and every test known to man. They only respond to drinking water. My pdoc says that sometimes doing something different can break the symptoms of an anxiety attack.
The Alprazolam and Clonazepan don't seem to work and if the water doesn't either I am bound for the ER.