The coronary arteries give our heart muscle its required oxygen-rich blood supply. Unfortunately, these arteries generally become narrow when someone develops a coronary artery disease, and the blood supply gets blocked, causing a heart attack.
Plaque formation depends on fat, proteins, calcium, and inflammatory cells, and these plaque deposits are generally soft on the inside and hard on the outside. The outer shell cracks in case the plaque is hard, leading to blood clot formation. Often, these blood clots block the artery, and the heart muscle automatically starts looking for oxygen.
A spasm in the coronary artery can also be a major reason for a heart attack. This can happen even if the person does not have coronary disease.