 Hi, this is Dr. Anand Shanai, Interventional Cardiologist, Manipal Hospitals, Bangalore. Now, the exact mechanism what happens when you have persons of us heart attack is, complete stoppage of blood flow to one of the, normally the heart has got three arteries, and these arteries are called coronary arteries which supply blood to the heart. So, when you get complete stoppage of blood flow to one of the arteries, you get a heart attack, what we call as HD elevation myocardial infarction. We get a partial reduction in blood flow, like say 90% reduction, 80% reduction, we get what is called as acute coronary syndrome. Now, why does this phenomenon of acute reduction in blood flow to the heart muscle happen? The reason is, when we have plaque or cholesterol buildup in the heart, which is supplied to the heart, which is coronary arteries, which we call ethrosclerosis, which is basically a fat deposition that causes a narrowing of the diameter of the vessel. Basically, that when it becomes aggravates acutely due to a clot formation over this blockade, you get complete stoppage of blood flow to the heart, which causes a heart attack.