Coronary artery disease is plaque buildup in the walls of blood vessels that supply blood to the heart. It takes years to develop and may not cause problems unless extreme narrowing occurs or plaque ruptures. With extreme narrowing, blood flow to the heart becomes partially blocked. Partial blockage causes chest pain with activity that goes away at rest (stable exertional angina). This is less serious than plaque rupture, which triggers formation of a blood clot and causes blood flow to the heart to become totally blocked. Blockage causes heart muscle damage, also known as a heart attack (myocardial infarction), or sudden death. Risk factors for these events include high blood pressure, high cholesterol level, diabetes, and smoking. Treatments for these risk factors can prevent coronary artery disease. Whether the treatments have different effects on the chance of developing stable angina, heart attack, or sudden death is not known.