I don't know of a heart attack called a 'mini heart attack' and I suspect you are thinking of what is commonly know as a silent heart attack. This is one that can occur without a person even realising it, and it's more common in women.
Here, a (proper name, silent ischemia) a lack of oxygen to the heart muscle causes damage. The symptoms of mild chest pain, indigestion/nausea sensations and pain travelling to the arm may be shrugged off, but they shouldn't be. Medical attention is needed as rapidly as if the pain were severe.