Causes
In the great majority of cases, angina is caused by coronary artery disease (CAD). The coronary arteries are the heart muscle's blood and oxygen supply. In CAD, the coronary arteries become narrowed by fatty, fibrous deposits. This reduces the quantity of blood that can pass through them. During exercise or exertion, the cells in the heart (the myocardium) may need more oxygen (and therefore more blood) than the coronary arteries can handle. As these cells are forced to work with inadequate resources, the nervous system complains by sending pain signals to the brain.
When tissue is denied adequate oxygen, it's called ischemia. Angina is therefore usually caused by myocardial ischemia (inadequate oxygen in the heart muscle). This isn't the same as myocardial infarction (heart attack). Infarction is the term for permanent cell death caused by prolonged and severe ischemia. In angina, the cells aren't usually so starved of oxygen that they die. This is why rest or medication is usually effective in relieving the pain.
Heart attacks are normally provoked by particular events that completely obstruct blood flow in a coronary artery. Such events include traveling blood clots or peeling off of fatty plaques inside the arteries. In angina, there's no sudden obstruction, but the normal diameter of the artery is no longer big enough to handle the demands of strenuous exercise. This usually means it has lost more than half of its internal diameter. It follows that people who suffer from angina are at elevated risk of heart attack. For unknown reasons, angina seems to have a better prognosis in women than in men.
Risk factors for angina are basically the same as risk factors for coronary artery disease. They include:
- high blood pressure
- being male
- diabetes
- poor cholesterol profile
- smoking
- low fitness
- obesity
- high salt intake
- excessive alcohol use
- women who are post-menopausal
- family history of early CAD, stroke, or other circulation-related medical conditions
Not all angina is due to coronary artery disease. A minority of cases are caused by spasms in coronary arteries that constrict them enough to seriously reduce blood flow. This can be caused by drugs, especially cocaine. In most cases, however, the cause is unknown. This condition, known as variant angina, isn't usually a sign of high heart attack risk on its own, but it generally occurs in people who also have coronary artery disease.