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What is Coronary Artery Disease (CAD)?
Coronary artery disease (CAD), also known as coronary heart disease, is a condition in which a waxy substance called plaque builds up inside the coronary arteries. These are the blood vessels that supply oxygen-rich blood to the heart muscle.
The buildup of plaque within the arteries is a process called atherosclerosis and develops over many years.
Over time, plaque can harden or rupture:
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Hardened plaque causes the coronary arteries to narrow, significantly reducing the flow of oxygen-rich blood to the heart.
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If the surface of the plaque breaks open, a blood clot (thrombus) can form. A large clot can partially or completely block blood flow through a coronary artery. Over time, the ruptured plaque also hardens and further narrows the artery.
Reduced or blocked blood flow to the heart muscle can lead to angina or a heart attack:
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Angina refers to chest discomfort or pain. It can feel like pressure or squeezing in the chest, but sometimes the discomfort extends to the shoulders, arms, neck, jaw, or back. Angina pain can also mimic indigestion.
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A heart attack occurs when the flow of oxygen-rich blood to a section of heart muscle is suddenly blocked. If blood flow is not restored quickly, that part of the heart muscle begins to die. Without prompt treatment, a heart attack can have serious consequences or even be fatal.
Over time, the progressive narrowing of the coronary arteries can weaken the heart muscle, leading to heart failure and arrhythmias:
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Heart failure is a condition in which the heart cannot pump enough blood to meet the body’s needs.
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Arrhythmias are changes in the normal rhythm or rate of the heartbeat.
Lifestyle changes, medications, and medical procedures can help prevent or treat coronary artery disease and reduce the risk of related health problems.
The Heart
The heart is a muscle about the size of your fist.
Its job is to pump blood throughout the body, contracting on average about 70 times per minute.
After blood leaves the right side of the heart, it enters the lungs where it picks up oxygen.
The oxygen-rich blood returns to the heart and is pumped out to the body’s organs through a network of arteries. Blood returns to the heart through veins before being pumped to the lungs again. This process is called circulation.
To work properly, the heart receives its own blood supply from a network of blood vessels on its surface, the coronary arteries.
Causes
The most widely accepted theory is that coronary artery disease begins with damage to the inner lining of the coronary arteries. This damage may be caused by:
- smoking,
- high blood levels of certain fats and cholesterol,
- high blood pressure (hypertension),
- high blood glucose levels (hyperglycemia) due to insulin resistance or overt diabetes,
- inflammation of blood vessels.
Plaque buildup may begin where the arteries are damaged. A single coronary plaque may even start forming during childhood.
Over time, plaque can harden or rupture:
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Hardened plaque narrows the coronary arteries and reduces blood flow to the heart, potentially causing angina (chest pain or discomfort).
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If plaque ruptures, platelets (cell fragments in the blood) stick to the injury site and can clump together to form blood clots.
These clots can further narrow the coronary arteries and worsen angina. A clot that is large enough can mostly or completely block a coronary artery and cause a heart attack.
Risk Factors
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Abnormal blood cholesterol levels: These include high levels of LDL cholesterol (“bad” cholesterol) and low levels of HDL cholesterol (“good” cholesterol).
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High blood pressure: Blood pressure is considered high when it consistently stays above 140/90 mmHg (some recent guidelines set even lower thresholds). In people with diabetes or chronic kidney disease, the target is lower, at 130/80 mmHg (mmHg stands for millimeters of mercury, the unit used to measure blood pressure).
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Smoking: Smoking can damage and tighten blood vessels, raise LDL cholesterol levels, and increase blood pressure. Smoking also reduces the amount of oxygen that reaches the body’s tissues by affecting the efficiency of red blood cells (via reduced oxygen saturation).
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Insulin resistance: In this condition, the body cannot properly use insulin, a hormone that helps move glucose from the blood into cells where it is used for energy. Insulin resistance can progress to diabetes.
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Diabetes: In this disease, blood sugar is too high because the body does not produce enough insulin or does not use it effectively.
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Overweight or obesity: These terms refer to a body weight that is greater than what is considered healthy for a given height.
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Metabolic syndrome: This is the name for a group of risk factors that increase the chances of developing coronary artery disease and other health problems, such as diabetes and stroke.
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Physical inactivity: Lack of physical activity can worsen other risk factors for coronary artery disease, such as abnormal cholesterol levels, high blood pressure, diabetes, and overweight or obesity.
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Unhealthy diet: A poor diet can raise the risk of coronary artery disease. Foods high in saturated and trans fats, cholesterol, salt, and sugar can worsen other risk factors.
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Older age: In men, the risk for coronary artery disease increases significantly after age 45. In women, the risk increases after age 55.
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A family history of early coronary artery disease is a risk factor, especially if heart disease was diagnosed in a father or brother before age 55, or in a mother or sister before age 65. Although older age and a family history of early CAD are risk factors, neither means that the disease will necessarily develop.
Managing other risk factors can often reduce genetic influences and help prevent coronary artery disease, even in older adults.
Scientists continue to study other possible risk factors for coronary artery disease. High blood levels of a protein called C-reactive protein (CRP) may increase the risk of CAD and heart attack; high CRP levels signal inflammation in the body. Other markers, such as homocysteine, are also considered risk factors when too high.
Inflammation is the body’s response to injury or infection. Damage to the inner walls of arteries can trigger inflammation and promote plaque growth.
High blood levels of triglycerides can also raise the risk of coronary artery disease, especially in women. Triglycerides are a type of fat found in the blood.
Other Risks Related to Coronary Artery Disease
Other conditions can contribute to coronary artery disease, including:
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Sleep apnea: Sleep apnea is a common disorder marked by one or more pauses in breathing or shallow breathing during sleep. If left untreated, it can increase the risk of high blood pressure, diabetes, and even heart attack or stroke.
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Stress: Research has shown that the most common trigger of a heart attack is an emotionally upsetting event, particularly one involving anger.
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Alcohol: Heavy drinking can damage the heart muscle and worsen other risk factors for coronary artery disease. Men should have no more than two alcoholic drinks per day, and women no more than one.
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Preeclampsia: This is a condition that can develop during pregnancy. Its two main signs are a rise in blood pressure and excess protein in the urine. Preeclampsia is linked to a higher lifetime risk of heart disease, including coronary artery disease, heart attack, heart failure, and high blood pressure.
Symptoms
Some people with coronary artery disease have no signs or symptoms. This is called silent coronary artery disease. The disease may not be diagnosed until signs and symptoms of a heart attack, heart failure, or arrhythmia (irregular heartbeat) appear.
A common symptom is angina, chest pain or discomfort that occurs when an area of the heart muscle does not receive enough oxygen-rich blood.
It may feel like pressure or a squeezing sensation in the chest. The discomfort can also spread to the shoulders, arms, neck, jaw, or back. Angina pain can feel like indigestion. It tends to get worse with activity and go away with rest. Emotional stress can also trigger the pain.
Another common symptom of coronary artery disease is shortness of breath. This symptom arises when CAD causes heart failure. In heart failure, the heart cannot pump enough blood to meet the body’s needs, and fluid builds up in the lungs, making breathing difficult.
The severity of symptoms varies and can increase as the coronary arteries progressively narrow due to plaque buildup.
Heart Attack
A heart attack occurs when the flow of oxygen-rich blood to a section of heart muscle is cut off. This can happen if a piece of plaque in a coronary artery ruptures or if a plaque simply grows large enough to block the vessel.
Regardless of the cause, if the blockage is not quickly treated, the part of the heart muscle that depends on that artery begins to die. Healthy heart tissue is replaced by scar tissue. Depending on the extent of the damage, the heart may compensate with no symptoms, or symptoms may appear in full severity, possibly leading to death.
The most common symptom is chest pain or discomfort. Most heart attacks involve discomfort in the center or left side of the chest that lasts for more than a few minutes or that goes away and comes back.
The discomfort can feel like uncomfortable pressure, squeezing, fullness, or pain. The feeling can be mild or severe. Heart attack pain can sometimes feel like indigestion or heartburn.
Angina symptoms and heart attack symptoms can be similar, but angina usually lasts only a few minutes and disappears with rest. Chest pain or discomfort that does not go away or that changes pattern (for example, occurs more often or at rest) may be a sign of a heart attack. If you have any doubts, call emergency services immediately.
Any chest pain should be evaluated by a medical professional.
Other common signs and symptoms of a heart attack include:
- Discomfort in one or both arms, the back, neck, jaw, or upper stomach.
- Shortness of breath, which may occur before or along with chest discomfort.
- Nausea, vomiting, feeling faint (lightheadedness) or sudden loss of consciousness, breaking out in a cold sweat.
- Sleep disturbances, fatigue, or lack of energy.
A non-fatal heart attack can still cause permanent complications, including heart failure. The term “heart failure” does not mean the heart has stopped or is about to stop working; it means the heart cannot pump effectively and efficiently. Common symptoms include:
- shortness of breath or difficulty breathing,
- fatigue,
- and swelling in the ankles, feet, legs, stomach area, and veins in the neck.
These symptoms all result from fluid buildup in the body. At first, there may be tiredness or shortness of breath with usual physical activities, such as climbing a flight of stairs.
Arrhythmias
Arrhythmias are changes in the normal rhythm of the heartbeat. They may feel like a skipped beat or a heartbeat that is too fast.
Some people describe a fluttering feeling in the chest. These sensations are called palpitations.
Some arrhythmias can cause the heart to suddenly stop beating. This condition is called sudden cardiac arrest, which is usually fatal if not treated within minutes.
Diagnosis
The diagnosis of coronary artery disease is based on personal and family medical history, risk factors, a physical exam, and the results of tests and procedures.
No single test can diagnose CAD. If coronary artery disease is suspected, the doctor may recommend one or more of the following tests.
ECG (Electrocardiogram)
An ECG is a simple, painless test that detects and records the heart’s electrical activity. It shows how fast the heart is beating and whether the rhythm is steady or irregular. The ECG also records the strength and timing of electrical signals as they pass through the heart.
An ECG can reveal signs of heart damage due to CAD as well as signs of a current or previous heart attack.
Stress Test
This test measures the heart’s activity during physical exercise to make the heart work harder and beat faster. For people who cannot exercise, medicine is given to raise the heart rate.
When the heart works harder and beats faster, it needs more blood and oxygen. Arteries narrowed by plaque may not be able to supply enough oxygen-rich blood.
A stress test can show signs and symptoms of coronary artery disease, such as:
- Abnormal changes in heart rate or blood pressure,
- Shortness of breath or chest pain,
- Irregular heartbeats or abnormal electrical activity in the heart.
Sometimes a person cannot exercise long enough for their age because the heart does not receive enough oxygen-rich blood. However, other factors (e.g., lung disease, anemia, poor fitness) can also reduce exercise capacity.
Some stress tests take pictures of the heart while exercising and at rest. These imaging stress tests can show how well blood is flowing in the heart and how well the heart pumps.
Echocardiography
Echocardiography uses sound waves to create moving pictures of the heart. The images show the size and shape of the heart as well as how well the heart chambers and valves are working.
Echocardiography can also reveal areas of the heart with poor blood flow, areas of heart muscle not contracting normally, and previous injury to the heart muscle caused by reduced blood flow.
Chest X-ray
A chest X-ray takes pictures of the organs and structures inside the chest, including the heart, lungs, and blood vessels. It can show signs of heart failure, as well as lung problems and other causes of symptoms related to coronary artery disease.
Blood Tests
Blood tests check the levels of:
- fats and cholesterol,
- blood sugar,
- certain proteins in the blood.
Abnormal levels may signal an increased risk of coronary artery disease.
Coronary Angiography and Cardiac Catheterization
If other tests and risk factors suggest a high likelihood of coronary artery disease, the doctor may recommend coronary angiography (or coronarography). This test uses a special dye and X-rays to see the inside of the coronary arteries.
To get the dye into the coronary arteries, a procedure called cardiac catheterization is performed. A long, thin, flexible tube (catheter) is inserted into a blood vessel in the arm, groin, or neck and threaded to the coronary arteries. The dye is then injected, and X-ray images show how the dye flows through the arteries.
This procedure is usually done in a hospital while the patient is awake. It causes little to no pain, although some soreness may be felt where the catheter was inserted.
Treatment
Treatment for coronary artery disease includes lifestyle changes, medications, medical procedures, and cardiac rehabilitation.
Treatment goals may include:
- reducing the risk of blood clots forming (which can cause a heart attack),
- preventing complications of CAD,
- reducing risk factors to slow, stop, or reverse plaque buildup,
- relieving symptoms,
- widening or bypassing blocked arteries.
Lifestyle Changes
The doctor may recommend adopting a heart-healthy lifestyle. Changes can include:
- following a healthy diet,
- maintaining a healthy weight,
- managing stress,
- getting regular physical activity,
- quitting smoking.
Heart-Healthy Eating
A heart-healthy diet includes:
- fat-free or low-fat dairy products,
- fish rich in omega-3 fatty acids, such as salmon, tuna, and trout, at least 2-3 times per week,
- fruits, such as apples, bananas, oranges, pears, and prunes,
- legumes, such as beans, chickpeas, lentils, peas, and fava beans,
- vegetables, such as broccoli, cabbage, and carrots,
- whole grains (whole-wheat bread, pasta, and brown rice, as well as grains eaten as soups or salads).
A heart-healthy diet should limit:
- excessive amounts of red meat,
- palm and coconut oils,
- sugary foods and beverages.
Two types of fats raise blood cholesterol levels:
- saturated fats, mainly found in animal products,
- trans fats, typically found in foods made with hydrogenated oils and fats, such as margarine, baked goods like cookies, cakes, and pastries, crackers, frostings, and cream. Some trans fats also occur naturally in animal fats and meats.
Not all fats are harmful. In fact, monounsaturated and polyunsaturated fats help lower blood cholesterol levels. Foods that contain these healthy fats include:
- avocados,
- corn, sunflower, and soybean oils,
- nuts and seeds, like walnuts,
- olive, canola, peanut, safflower, and sesame oils,
- salmon and trout,
- tofu.
Sodium
Try to limit sodium intake. Choose and prepare foods with little salt and sodium. Use low-sodium products and do not add salt or salty seasonings at the table or during cooking. Food labels provide the information needed to select lower-sodium options. Aim to consume no more than 2,300 mg of sodium per day. If you have high blood pressure, you may need to reduce sodium even further.
The DASH Eating Plan
DASH stands for Dietary Approaches to Stop Hypertension. Your doctor may suggest following the DASH eating plan, which emphasizes fruits, vegetables, whole grains, and other heart-healthy foods that are low in fat, cholesterol, sodium, and salt. DASH is a good example of a healthy eating plan, even for people who do not have high blood pressure.
Alcohol
Try to limit alcohol intake. Alcohol can raise blood pressure and triglyceride levels (a type of fat in the blood). It also adds calories that can contribute to weight gain.
Men should have no more than two alcoholic drinks per day, and women no more than one. One drink is:
- 12 ounces (about 350 ml) of beer,
- 5 ounces (about 150 ml) of wine,
- 1.1-1.5 ounces (33-44 ml) of liquor, depending on proof.
Body Weight
Maintaining a healthy weight is important for overall health and can lower the risk of coronary artery disease. Aim for a healthy weight by following a wholesome eating plan and staying physically active.
Knowing your body mass index (BMI) helps determine whether your weight is appropriate for your height and gives an estimate of total body fat.
A BMI:
- below 18.5 indicates underweight,
- between 18.5 and 24.9 is considered normal,
- between 25 and 29.9 indicates overweight,
- 30 or higher indicates obesity.
Try to achieve a BMI under 25. Your doctor will help you set an appropriate goal.
Waist measurement also helps predict health risks. If most of your body fat is around your waist rather than your hips, you have a higher risk of coronary artery disease and type 2 diabetes. The risk increases with a waist measurement greater than 35 inches (89 cm) in women or 40 inches (102 cm) in men.
If you are overweight or obese, try to lose weight. A reduction of just 3-5% of your body weight can lower triglycerides, blood sugar, and the risk of developing type 2 diabetes. Greater weight loss can also improve blood pressure, lower LDL cholesterol, and raise HDL cholesterol.
Stress
Research has shown that the most common trigger of a heart attack is an emotionally upsetting event, especially one involving anger. Also, some common ways of coping with stress, such as drinking, smoking, or overeating, are unhealthy.
Learning to manage stress, relax, and address problems can improve both emotional and physical health. Consider stress-reducing activities such as:
- meditation,
- physical activity,
- relaxation therapy,
- talking with friends or family.
Physical Activity
Regular physical activity can lower many risk factors for coronary artery disease, including LDL cholesterol, blood pressure, and excess weight. Exercise can also lower the risk of diabetes and raise HDL cholesterol levels. HDL is the “good” cholesterol that helps prevent CAD.
Everyone should aim for at least 150 minutes of moderate-intensity aerobic exercise per week, or 75 minutes of vigorous aerobic activity per week. Aerobic activity, such as brisk walking, is any exercise that causes your heart to beat faster and your body to use more oxygen. The more active you are, the greater the benefits. Spread the activity throughout the week in sessions of at least 10 minutes each.
Talk to your doctor before starting a new exercise plan. Ask about the right types and amounts of activity for your condition.
Quitting Smoking
Stop smoking. Smoking raises the risk of coronary artery disease and heart attack and worsens other risk factors. Ask your doctor about programs and products that can help you quit. Also try to avoid secondhand smoke.
If quitting on your own is difficult, consider joining a support group. Many hospitals and community organizations offer services to help people become smoke-free.
Medications
Sometimes lifestyle changes alone are not enough to control cholesterol levels. You may need to take statins to control or lower cholesterol. Lowering cholesterol can reduce the risk of heart attack or stroke. Statins are usually prescribed for people with:
- coronary artery disease, peripheral artery disease, or a history of stroke,
- diabetes,
- very high LDL cholesterol levels.
Statin therapy is also considered for people with a high risk of developing heart disease or stroke.
Other medications may also be prescribed to:
- reduce the risk of heart attack or sudden death,
- lower blood pressure,
- prevent blood clots that can cause a heart attack or stroke,
- prevent or delay the need for a stent, coronary angioplasty, or surgery such as coronary bypass,
- reduce the heart’s workload and relieve symptoms of CAD.
Take all medications exactly as prescribed, regularly. Do not change doses or skip doses unless your doctor tells you to. Even while taking medication, you must continue following a heart-healthy lifestyle.
Medical Procedures and Surgery
Treating coronary artery disease may require a medical procedure or surgery. Both angioplasty and coronary artery bypass grafting (CABG) are used to treat blocked coronary arteries. The specific treatment will be chosen based on your individual condition.
Percutaneous Coronary Angioplasty
This is a non-surgical procedure that opens narrowed or blocked coronary arteries. A thin tube with a deflated balloon on the tip is threaded through a blood vessel to the narrowed or blocked coronary artery. Once in place, the balloon is inflated to push the plaque against the artery wall, restoring blood flow.
During this procedure, a small mesh tube called a stent may also be placed in the artery to help keep it open and prevent it from narrowing again in the months or years following angioplasty.
Coronary Artery Bypass Grafting (CABG)
CABG is a type of surgery in which arteries or veins from elsewhere in the body are used to “bypass” or go around the blocked coronary arteries. The bypass improves blood flow to the heart, can relieve chest pain, and may help prevent a heart attack.
Cardiac Rehabilitation
Cardiac rehabilitation is usually recommended for people who have angina or who have had bypass surgery, angioplasty, or a heart attack. Almost anyone with coronary artery disease can benefit from rehabilitation. It is a medically supervised program that can help improve the health and well-being of people with heart problems.
A cardiac rehabilitation team typically includes doctors, nurses, exercise specialists, physical and occupational therapists, dietitians or nutritionists, and psychologists or other mental health professionals.
Rehabilitation has two main parts:
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Education, counseling, and training: This part helps you understand your heart condition and find ways to reduce the risk of future heart problems. The team will teach you how to cope with the stress of adjusting to a new lifestyle and to manage fears about the future.
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Exercise training: This part helps you exercise safely, strengthen your muscles, and improve your stamina. Your exercise plan will be based on your individual ability, needs, and interests.
Prevention
You can prevent or control coronary artery disease by managing your risk factors through lifestyle changes and medications. Examples of controllable risk factors include:
- cholesterol levels,
- blood pressure,
- overweight and obesity.
Only a few risk factors, such as age, sex, and family history, cannot be controlled.
The risk of coronary artery disease increases with the number of risk factors a person has. To reduce your risk of CAD and heart attack, try to control each risk factor by adopting the following lifestyle habits:
- eating a heart-healthy diet,
- maintaining a healthy weight,
- managing stress,
- getting regular physical activity,
- quitting smoking,
- knowing your family history of early CAD.
Remember to tell your doctor if anyone in your family has had coronary artery disease. If lifestyle changes are not enough to control your risk factors, your doctor may prescribe medications.
