Cholesterol is a major ingredient of the plaque that builds up in the coronary arteries and causes heart disease, so it is important to understand how plaques develop. Excess cholesterol is deposited in the artery walls as it travels through the bloodstream. Then, special cells in the artery wall gobble up this excess cholesterol, creating a "bump" in the artery wall. This cholesterol-rich "bump" then is covered by a scar that produces a hard coat or shell over the cholesterol and cell mixture. It is this collection of cholesterol covered by a scar that is called plaque.
 
The plaque buildup narrows the space in the coronary arteries through which blood can flow, decreasing the supply of oxygen and nutrients to the heart. If not enough oxygen- carrying blood can pass through the narrowed arteries to reach the heart muscle, the heart may respond with a pain called angina. The pain usually happens with exercise when the heart needs more oxygen. It is typically felt in the chest or sometimes in other places like the left arm and shoulder. However, this same inadequate blood supply may cause no symptoms.
 
Plaques come in various sizes and shapes. Throughout the coronary arteries many small plaques build themselves into the walls of the arteries, blocking less than half of the artery opening. These small plaques are often invisible on many of the tests doctors use to identify coronary heart disease. It used to be thought that the most dangerous plaques and the ones most likely to cause total blockage of coronary arteries were the largest ones. The largest plaques are in fact the ones most likely to cause angina. However, small plaques that are full of cholesterol and covered by a scar are now thought to be very unstable and more likely to rupture or burst, releasing their cholesterol contents into the bloodstream. When this happens, it triggers blood clotting inside the artery. If the blood clot totally blocks the artery, it stops blood flow and a heart attack occurs. The muscle on the far side of the blood clot does not get enough oxygen and begins to die. The damage can be permanent.
 
Lowering your blood cholesterol level can slow, stop, or even reverse the buildup of plaque. Cholesterol lowering can reduce your risk of a heart attack by lowering the cholesterol content in unstable plaques to make them more stable and less prone to rupture. This is why lowering your LDL-cholesterol is such an important way to reduce your risk for having a heart attack. Even in people who have had one heart attack, the chances of having future attacks can be substantially reduced by cholesterol lowering.