Approximately 7-10% of cases of ACS are not related to atherosclerotic coronary disease. Some other causes of ACS include the following:
trauma
vasculitis
congenital abnormalities
emboli (e.g. bacterial)
thoracic aortic dissection
infectious diseases
DIC, TTP
These conditions can produce ST-segment changes that resemble those of true STEMI or non-STEMI, and therefore some of these patients are diagnosed retrospectively after a negative catheterization.