Coronary artery disease (CAD) is a condition in which sticky deposits, called plaques, build up in the walls of the coronary arteries (the vessels that supply blood to the heart muscle).
These plaques can gradually obstruct the artery, or they can suddenly rupture, causing a more acute obstruction.
Because the heart muscle requires a continuous supply of oxygen and nutrients to survive, obstruction of a coronary artery rapidly leads to significant problems.
Coronary Artery Disease is caused by atherosclerosis.
- Atherosclerosis is a chronic, progressive disorder of the arteries in which deposits of cholesterol, calcium, and abnormal cells (that is, plaques) build up on the inner lining of the arteries.
These plaques can cause a gradual but progressive narrowing of the artery, and as a result, blood flow through the artery becomes more difficult. When the obstruction becomes large enough, the patient may experience angina.
“Angina ” refers to the symptoms patients experience any time the heart muscle is not getting enough blood flow through the coronary arteries. Angina is usually felt as a discomfort (often a pressure-like pain) in or around the chest, shoulders, neck or arms.
- “Stable angina ” is angina that occurs in a nearly predictable fashion, for instance, with exertion or after a big meal. Stable angina generally means that a plaque has become large enough to produce a partial obstruction of a coronary artery.
When a person with stable angina is at rest, the partially blocked artery is able to meet the needs of the heart muscle. But when that person exercises, (or has some other stress that makes the heart work harder), the obstruction prevents an adequate increase in blood flow to the heart muscle, and angina occurs.
So stable angina usually means there that there is a significant plaque buildup in a coronary artery that is partially obstructing the flow of blood.
In addition to causing obstruction by a gradual increase in their size, plaques are also subject to sudden rupture, which can produce a very sudden obstruction.
The medical conditions caused by the rupture of a plaque are referred to as Acute Coronary Syndrome (ACS). ACS is always a medical emergency.
“Unstable angina ” is one type of ACS. It occurs when a plaque has partially ruptured, causing a sudden worsening of the blockage in the artery.
- In contrast to stable angina, symptoms in unstable angina occur unpredictably, (that is, they are not particularly related to exertion or stress), and notably, tend to occur at rest. (Another name for unstable angina is “rest angina.”)
Patients with unstable angina are at high risk of developing a total occlusion of the coronary artery, leading to a myocardial infarction.
Myocardial infarction, or heart attack, is a more dire form of ACS.
- Here, the ruptured plaque causes a total (or near total) occlusion of the coronary artery, so that the heart muscle supplied by that artery dies.
- A heart attack, therefore, is the death of heart muscle.
The seriousness of a myocardial infarction depends largely on how much heart muscle has died. A small heart attack is one in which only a small part of the heart muscle dies. A large heart attack is one in which a large part of heart muscle dies.
In this figure, arterial narrowing threatens to cause a heart attack with real muscle loss.
If a patient receives medical attention within a few hours of the onset of a heart attack, the size of the heart attack can be greatly reduced by administering “clot-busting drugs,” or by performing an immediate angioplasty (and most often, stenting ) to open up the blocked artery.
- Angioplasty works by inflating a tiny balloon within the artery at the site of an atherosclerotic plaque, flattening the plaque and reducing the stenosis (blockage) within the artery.
After surviving a heart attack, the patient is still at risk.
Subsequent heart attacks are possible if more plaques are present in the coronary arteries. Also, depending on the amount of heart muscle that has been damaged, the patient can develop heart failure (a condition in which the heart is unable to keep up with the body’s needs).
Furthermore, the damaged heart muscle can cause a permanent instability in the heart’s electrical system, which can lead to sudden cardiac arrest.
So after a heart attack, all of these risks need to be carefully evaluated, and steps need to be taken to reduce each of these to the greatest extent possible.
The best way to deal with coronary artery disease, of course, is to prevent it. It’s important to do everything we can to reduce our CAD risk factors.
Controllable Risk Factors
We can greatly diminish our risk of heart attack and cardiac death by paying careful attention to the following risk factors:
- Smoking. While smoking is the chief cause of heart attacks in people under the age of 40, it is a strong risk factor at any age.
- High cholesterol and triglycerides. High LDL cholesterol, total cholesterol, and triglycerides, and low HDL cholesterol levels, are associated with a significantly increased risk of heart attack.
- Obesity. Being overweight, and especially having a big belly, has been associated with an increased risk of heart attack.
- Lack of exercise. People who exercise regularly have a reduced risk of heart attack.
- Hypertension. High blood pressure is a major risk factor for heart attack, and especially stroke. Hypertension is very common in Americans over the age of 55 but is commonly inadequately treated.
- Diabetes. Diabetes is becoming much more frequent in the U.S., as the population becomes more overweight. Diabetes – specifically, the higher blood sugars and the other metabolic abnormalities that go with this disease – greatly accelerates the development of atherosclerosis.
- Metabolic syndrome. Metabolic syndrome, or pre-diabetes, is also strongly associated with increased cardiac risk.
- Increased C-reactive protein (CRP). CRP is a relatively “new” risk factor.
Increased levels of CRP show active inflammation somewhere in the body, and unless some obvious source of inflammation is seen elsewhere (such as active arthritis), elevated CRP is thought to show inflammation in the blood vessels – which goes along with atherosclerosis.
- Psychological stress. Stress has been linked to heart attacks for many years. But some stress in life is unavoidable – and is even a good thing in many cases.
Additional Risk Factors in Women
Here are two more risk factors that are specific to women:
- Taking birth control pills, especially among smokers.
Birth control pills have been associated with a small increase in the risk of early heart attack in women. But when birth control pills are combined with smoking, there is a very large increase in risk. In fact, it is now clear that women who smoke simply should not take birth control pills.
- Complicated pregnancy. Women who develop certain complications during pregnancy – specifically, women who develop high blood pressure (a condition called preeclampsia) or gestational diabetes (diabetes during pregnancy), or who deliver low-birth-weight babies – have an increased risk of early heart attack.
- Because complicated pregnancies identify women who are at increased risk, these women should manage all their controllable risk factors very aggressively.
For those who already have CAD, reducing these same risk factors becomes even more important, to slow the progression of the disease.
In addition, several avenues are available for treating CAD, including drug therapy, surgical therapy, angioplasty, and stenting.
The treatment of CAD always needs to be individualized, and optimal therapy depends on careful consideration of all the options, by both the doctor and the patient.