Coronary heart disease (CHD) is a very common and often "silent killer" of hundreds of thousands of people per year. It is a disease that affects the coronary arteries, which run along the outside of the heart. The function of these vessels is to provide the heart organ with oxygen rich blood to keep it rich of oxygen, nutrients and remove carbon dioxide. The most common form of heart disease is caused by arteriosclerosis, generally known as coronary heart disease, hardening and/or thickening of the arteries. This process involves the slow buildup of deposits of fatty substances, cholesterol, body cellular waste products, and calcium in the inside lining of an artery. The buildup that results, called plaque, may partially or totally block the blood's flow through the artery. This can lead to the formation of a blood clot (thrombus) on the plaque's surface. If either of these occurs and blocks the entire artery, a heart attack or stroke may result. There are many different risk factors involved in coronary heart disease, which include high cholesterol, high blood pressure, high stress, alcohol, diabetes, obesity, family history, sex, age, and smoking. Most of the causes and risk factors that lead to coronary heart disease are those that can be avoided by making good personal lifestyle choices. However, most people do not realize this until after it is too late. This is why secondary care and prevention has become a very important aspect in patients who have already suffered from heart attacks and other consequences of CHD. In a study done by Dr. Murchie et al. (2003) it was found that patients, who quit smoking, lowered fat intake, took aspirin, managed blood pressure and started a regular exercise program had a better chance of not experiencing a problem with their heart again. This study included a large sample size and waited one year before they checked up on any of their interventions.