Coronary heart disease (CHD) is a narrowing of the small blood vessels that supply blood and oxygen to the heart. Coronary heart disease is usually caused by a condition called atherosclerosis, which occurs when fatty material and a substance called plaque build up on the walls of your arteries. This causes them to get narrow. As the coronary arteries narrow, blood flow to the heart can slow down or stop. This can cause chest pain (stable angina), shortness of breath, heart attack, and other symptoms. Coronary heart disease (CHD) is the leading cause of deathIn atherosclerosis, fat and cholesterol in your blood builds up on an artery wall, forming a plaque or atheroma. The plaque can prevent the heart muscle from getting the blood supply (and therefore oxygen) that it needs. If you have atherosclerosis, physical exertion or emotional stress can bring on chest pain called angina (see What can coronary heart disease cause). Because of the reduced blood flow and the rough edges of the plaque, a blood clot sometimes forms. This can block the artery. Or the plaque may rupture, which also causes the blood to clot. This is called atherothrombosis. Atherothrombosis stops an area of the heart muscle receiving blood and oxygen, leading to permanent damage. This is called a myocardial infarction (MI), or heart attack. If a lot of your heart muscle is damaged your heart may stop beating regularly, or stop beating at all. This is fatal (see What can coronary heart disease cause). Bad genes (heredity) can increase your risk. You are more likely to develop the condition if someone in your family has had a history of heart disease -- especially if they had it before age 50. Your risk for CHD goes up the older you get. Diabetes is a strong risk factor for heart disease. High blood pressure increases your risk of coronary artery disease and heart failure. Abnormal cholesterol levels: your LDL ("bad") cholesterol should be as low as possible, and your HDL ("good") cholesterol should be as high as possible. Metabolic syndrome refers to high triglyceride levels, high blood pressure, excess body fat around the waist, and increased insulin levels. People with this group of problems have an increased chance of getting heart disease. Smokers have a much higher risk of heart disease than nonsmokers. Chronic kidney disease can increase your risk. Already having atherosclerosis or hardening of the arteries in another part of your body (examples are stroke and abdominal aortic aneurysm) increases your risk of having coronary heart disease.