Storage of cholesterol in coronary artery tends to heart attack. But in which phase heart attack occurs? Why only a definite time is called heart attack? Why this is the extreme point of coronary block?
Acute myocardial infarction (MI) usually happens when a coronary artery is abruptly occluded, typically by a blood clot. The clot can be an embolus that forms elsewhere (such as in the heart itself) and then happens to flow into a coronary artery, or more often it occurs when an atherosclerotic plaque (containing cholesterol) ruptures. Because a ruptured plaque looks a lot like tissues outside the blood vessels, the clotting machinery in the blood responds like it would to stop bleeding from a wound.
MI can also occur in other situations where blood flow is reduced to a level insufficient to supply the cardiac muscle with oxygen, without complete blockage, either from vasospasm or when increased activity (such as exercise) demands more flow than can be delivered through a narrowed atherosclerotic coronary artery.