Final answer:
MIs, or heart attacks, typically occur due to a blockage in the coronary arteries caused by plaque buildup. They are commonly caused by atherosclerosis.
Step-by-step explanation:
MIs (Myocardial Infarctions), also known as heart attacks, typically occur when there is a blockage in one or more of the coronary arteries that supply oxygen and nutrients to the heart muscle. The most usual cause of MIs is the buildup of plaque in the arteries, also known as atherosclerosis. This plaque can rupture, causing a blood clot that restricts blood flow to the heart, leading to a heart attack.