Any circumstance that suddenly impairs blood flow through the coronary arteries. Acute coronary syndrome includes all forms of acute myocardial infarction (i.e., those that cause Q waves on the electrocardiogram and those that do not, as well as those that cause S-T segment elevation and those that do not), and unstable angina pectoris.
An umbrella term that refers to a range of sudden heart conditions such as myocardial infarction that result from restricted blood flow to the heart.