arteries that supply blood and oxygen to the heart muscles are called coronary arteries. coronary artery disease (cad) occurs when cholesterol plaque (a hard thick substance comprised of varying amounts of cholesterol calcium muscle cells and connective tissue which accumulates locally in the artery walls) builds up in the walls of these arteries a process called arteriosclerosis. over time arteriosclerosis causes significant narrowing of one or more coronary arteries. when coronary arteries narrow more than 50 to 70% the blood supply beyond the plaque becomes inadequate to meet the increased oxygen demand during exercise. lack of oxygen (ischemia) in the heart muscle causes chest pain (angina) in most patients. however some 25% of patients experience no chest pain at all despite documented ischemia or may only develop episodic shortness of breath instead of chest pain. these patients have "silent angina" and have the same risk of heart attack as those with angina. when arteries are narrowed in excess of 90-99% patients often have angina at rest (unstable angina). when a blood clot (thrombus) forms on the plaque the artery may become completely blocked causing death of a part of the heart muscle (heart attack or myocardial infarction ). the arteriosclerotic process can be accelerated by smoking high blood pressure elevated cholesterol levels and diabetes. patients are also at higher risk for arteriosclerosis if they are older (greater than 45 years for men and 55 years for women) or if they have a family history of coronary heart disease.
how does coronary artery disease develop?