Updated June 09, 2015.

Definition:

Acute coronary syndrome is a group of syndromes that occur due to the abrupt rupture of atherosclerotic plaque in the coronary artery. This includes conditions such as unstable angina or a myocardial infarction (heart attack).

As cholesterol begins to build up on the inside of an inflamed vessel, it begins to form a thick plaque. As this plaque builds up, it has the potential to suddenly rupture.

This encourages the buildup of red blood cells, which can form a clot and limit -- or completely occlude -- blood flow to tissues and organs.