What causes angina pectoris?
Usually a stenotic coronary artery caused by atherosclerosis. The stenotic (narrowed) artery can give a brief period of ischemia (withholding of blood) to a region of the heart, which is felt as an intense pain. Angina pectoris is a sign that a more serious episode of ischemic attack can happen for that artery. If it is left untreated, it is very likely that the artery will eventually become completely clogged and the ensuing prolonged ischemia will cause a myocardial infarction (i.e. heart attack).
Angina takes place when there is a limited amount of blood flowing to a particular area of the heart. What happens is that there is less oxygen and nutrients sent to the cells of the heart muscle and this means that the heart has to look for fuel elsewhere. A less efficient type of fuel that ends up being used is a product called lactic acid that causes discomfort and also builds in strength in the muscles. Sometimes those suffering from aortic stenosis (a heart valve problem) will have less blood flowing to the arteries and sometimes those with a severe case of anemia might develop angina due to the fact that the blood is not carrying enough oxygen. Angina can also be felt by individuals who have thickened heart muscles due to lack of oxygen.