What is coronary artery disease (CAD)?
The most common type of heart disease is coronary artery disease (CAD), narrowing of coronary arteries. These are the blood vessels that supply blood and oxygen to the heart. The condition is also called coronary heart disease (CHD).
CAD is usually caused by atherosclerosis. Atherosclerosis is the buildup of cholesterol plaque inside the coronary arteries. These plaques are made up of fatty deposits, inflammatory cells, calcium, and fibrous tissue.
With narrowed arteries, flow of oxygen-rich blood to heart muscle slows. At rest, blood supply might be sufficient. But during exercise or periods of emotional stress, inadequate blood flow in a coronary artery can cause a type of chest pain called angina.
Atherosclerosis also can lead to rupture of the cholesterol plaque, which then triggers formation of a blood clot inside a narrowed coronary artery. Sudden stoppage of blood flow in a coronary artery usually leads to heart attack, causing significant damage to the heart.
The risk factors for atherosclerosis and CAD are basically the same. These risk factors include:
- high blood cholesterol level
- high level of LDL (bad) cholesterol
- high levels of triglycerides
- high levels of lipoprotein(a)
- high blood pressure (hypertension)
- family history of CAD at a younger age
- cigarette smoking
- physical inactivity
- inflammation, often detected by high levels of C-reactive protein, a marker in the blood.
CAD is the most common chronic, life-threatening illness in most of the world's developed nations.
Symptoms of coronary artery disease
In most people, the most common symptom of CAD is angina. Angina, also called angina pectoris, is a type of chest pain.
Angina usually is described as a squeezing, pressing or burning chest pain. It tends to be felt mainly in the center of the chest or just below the center of the rib cage. It also can spread to the arms (especially the left arm), upper abdomen, neck, lower jaw, or neck.
Other symptoms can include:
- dizziness or lightheadedness
A patient may mistake heart symptoms, such as burning chest pain and nausea, for indigestion.
There are two types of chest pain related to CAD. They are stable angina and acute coronary syndrome.
Stable angina. In stable angina, chest pain follows a predictable pattern. It usually occurs after:
- physical activity or exertion
- extreme emotion
- a large meal
- cigarette smoking
- exposure to extreme hot or cold temperatures.
Symptoms usually last one to five minutes. They disappear after a few minutes of rest. Stable angina is caused by a smooth plaque. This plaque partially obstructs blood flow in one or more coronary arteries.
Acute coronary syndrome (ACS). ACS is much more dangerous. In most cases of ACS, fatty plaque inside an artery has developed a tear or break. The uneven surface can cause blood to clot on top of the disrupted plaque. This sudden blockage of blood flow results in unstable angina or a heart attack.
In unstable angina, chest pain symptoms are more severe and less predictable than in stable angina. Chest pains occur more frequently, even at rest. They last several minutes to hours. People with unstable angina often sweat profusely. They develop aches in the jaw, shoulders and arms.
Many people with CAD, especially women and those with diabetes, do not have any symptoms. Or, they have unusual symptoms. In these people, the only sign of CAD may be a change in the pattern of an electrocardiogram (EKG). An EKG is a test that records the heart's electrical activity.
An EKG can be done at rest or during exercise (exercise stress test). Exercise increases the heart muscle's demand for blood. The body can't meet this demand when the coronary arteries are significantly narrowed. When the heart muscle is starved for blood and oxygen, its electrical activity changes. This altered electrical activity affects the patient's EKG results.
In many people, the first symptom of coronary artery narrowing is a heart attack.
Diagnosing coronary artery disease
Coronary artery disease usually is diagnosed after a person has chest pain or other symptoms. However, screening for CAD with imaging is being done more commonly and can detect symptomatic disease earlier.
Your doctor will examine you, paying special attention to your chest and heart. Your doctor will press on your chest to see if it is tender. Tenderness could be a sign of a non-cardiac problem. Your doctor will use a stethoscope to listen for any abnormal heart sounds.
Your doctor will do one or more diagnostic tests to look for CAD. Possible tests include:
- An EKG. An EKG is a record of the heart's electrical impulses. It can identify problems in heart rate and rhythm. It can also provide clues that part of your heart muscle isn't getting enough blood.
- Blood test for heart enzymes. Damaged heart muscle releases enzymes into the bloodstream. Elevated heart enzymes suggest a heart problem.
- An exercise stress test. This test monitors the effects of treadmill exercise on blood pressure and EKG to identify heart problems. Exercise tests can also be done with echocardiogram or nuclear imaging to give you more precise information. These imaging stress tests can also be done using a medication for the stress component in patients who can't exercise.
- An echocardiogram. This test uses ultrasound to produce images of the heart's movement with each beat. It is used to look for evidence of prior heart attacks.
- Imaging test with radioactive tracers. In this test, a radioactive material is injected in the blood and shows where blood flows to the herat muscle.
- A coronary calcium scan. A special type of CT scan detects the amount of calcium in your arteries. Fatty deposits in the artery walls contain calcium. A higher score means more fatty deposits and coronary plaques. This indicates a higher risk of heart attack.
- A coronary angiogram. This is a series of X-rays of the coronary arteries. The coronary angiogram is the most accurate way to measure the severity of coronary disease. During an angiogram, a thin, long, flexible tube (catheter) is inserted into an artery in the forearm or groin. The tip of the tube is pushed up the body's main artery until it reaches the heart. Then it is pushed into the coronary arteries. Dye is injected to show blood flow within the coronary arteries. It also identifies any areas of narrowing or blockage.
- CT angiography of the heart. Dye is injected into a vein. A very fast CT scanner takes pictures as the dye moves through the coronary arteries. It can sometimes be performed instead of a coronary angiogram.
Expected duration of coronary artery disease
CAD is a long-term condition. People can have different patterns of symptoms.
Plaque in coronary arteries never will disappear completely. However, with diet, exercise and medication, the amount of cholesterol in the plaque can be reduced, and replaced with fibrous tissue, thereby stabilizing the plaques and making them less prone to rupture so they won't cause a heart attack. In addition, medication to lower heart rate and blood pressure can allow the demand for blood flow by the heart muscle to match any decrease in blood flow.
In addition, sometimes new, small blood channels called collaterals can develop to increase the blood flow to the heart muscle.
Preventing coronary artery disease
You can help to prevent CAD by controlling your risk factors for atherosclerosis. To do this:
- Quit smoking.
- Eat a healthy diet.
- Reduce your LDL (bad) cholesterol.
- Reduce high blood pressure.
- Lose weight.
Treating coronary artery disease
CAD caused by atherosclerosis is treated with one or more of the following treatments.
Lifestyle changes include:
- weight loss in obese patients
- quitting smoking
- diet and medications to lower high cholesterol and high blood pressure
- regular exercise
- stress reduction techniques, such as meditation and biofeedback.
Cholesterol-lowering medications. The choice of medication depends upon your cholesterol profile.
- Statins reduce the risk of heart attack and death in people with CAD and those at risk of CAD. Statins lower LDL cholesterol and may raise HDL cholesterol slightly. Taking a statin regularly also helps to reduce inflammation inside plaques of atherosclerosis. This is why doctors prescribe statins for people who have signs of inflammation, even if their cholesterol levels are normal. Examples of statins include atorvastatin (Lipitor), rosuvastatin (Crestor), simvastatin (Zocor), and pravastatin (Pravachol).
- Ezetimibe (Zetia) works within the intestine. It decreases the absorption of cholesterol from food.
- Bempedoic acid (Nexletol) reduces cholesterol production in the liver and increases clearance of LDL cholesterol from the blood.
- PCSK9 inhibitors are the most potent therapies to dramatically lower LDL cholesterol. People with coronary artery disease who either don't reach goal with a high-dose statin drug or cannot tolerate statins because of side effects may also be candidates for this therapy. PCSK9 inhibitors are much more expensive than most statins. Also, they are not available as pills. They must be injected once every two weeks. One type is given once every six months.
- For patients with elevated triglycerides, icosapent ethyl has been shown to reduce heart attacks and strokes.
Two classes of medications, niacin and fibrates, have been found not to reduce heart attacks and are no longer recommended for prevention. Sometimes they are used for patients with very high triglycerides (andgt;500 mg/dl). Gemfibrozil (Lopid) and fenofibrate (Tricor, many generic versions) are fibrates.
Aspirin. Aspirin helps to prevent blood clots from forming inside narrowed coronary arteries. It reduces the risk of heart attack in people who already have CAD. For patients without known CAD but with risk factors, doctors will review a patient's individual risk and discuss with them the relative benefits of preventing a heart attack or stroke versus the risk of bleeding.
Other types of anti-platelet drugs can be used instead of or in addition to aspirin, including clopidogrel (Plavix) and sometimes an anticoagulant (blood thinner) such as apixaban (Eliquis), rivaroxaban (Xarelto), or warfarin (Coumadin.
Beta blockers. These medications decrease the heart's workload. They do this by slowing the heart rate. They also reduce the force of heart muscle contractions, especially during exercise. People who have had a heart attack should stay on a beta blocker for life. This will reduce the risk of a second heart attack. Atenolol (Tenormin) and metoprolol (Lopressor) are beta blockers.
Calcium channel blockers. These medications may help to decrease the frequency of chest pain in patients with angina. Examples include nifedipine (Adalat, Procardia), diltiazem (Cardizem), and verapamil.
Nitrates (including nitroglycerin). These medications are vasodilators, which means they widen the coronary arteries to increase blood flow to the heart muscle. They also widen the body's veins. This lightens the heart's workload by temporarily decreasing the volume of blood returning to the heart.
Ranolazine. Ranolazine (Ranexa) can be prescribed in patients who continue to have chest pain with exertion (stable angina) despite using all of the therapies listed above.
Coronary artery angiography. Some people are physically limited by stable angina because of chest pain. In this case, your doctor likely will advise you to have a coronary artery angiography to look for significant blockages. This procedure is also called a cardiac catheterization.
Coronary stenting. When one or more significant blockages are found, the cardiologist will determine if the blockage(s) can be opened. He or she will consider a procedure called coronary stenting, where a metal mesh stent is placed inside the blockage to open it up and keep it open. Sometimes only a balloon angioplasty is done. These procedures are also called percutaneous coronary intervention (PCI).
In PCI, a catheter is inserted into an artery in the groin or forearm. The catheter is threaded into the blocked coronary artery. A metal mesh stent, usually with a small balloon inside it, is inflated briefly to open the narrowed blood vessel. The wire mesh remains inside the artery to keep it open. The balloon is deflated and the catheter is removed.
Coronary artery bypass surgery (CABG). If the blockages cannot be opened with balloon angioplasty, the cardiologist will likely suggest CABG.
CABG involves grafting one or more blood vessels onto the coronary arteries. This allows blood to bypass the narrowed or blocked areas. The blood vessels to be grafted can be taken from an artery inside the chest or arm, or from a long vein in the leg.
Treating heart attack or sudden worsening of angina
The goal of treating heart attacks or sudden worsening of angina is to rapidly restore blood flow to the section of heart muscle no longer getting blood flow.
Patients immediately receive:
- medication to relieve pain
- nitroglycerin to dilate the heart artery to try to improve blood flow
- a beta-blocker to slow the heart rate and decrease the work of the heart
- aspirin combined with other medications to dissolve or inhibit blood clotting.
For patients with a severe heart attack whose ECGs indicate a 100% blocked artery, patients are transferred immediately to a cardiac catheterization laboratory. There, they have an immediate angiography and coronary stenting of the most significant blockage. For other patients with acute coronary syndromes, the catheterization is usually done within the first few days.
In some people with CAD, other symptoms or complications will require additional treatment. For example, medication may be needed to treat abnormal heart rhythms or low blood pressure.
When to call a professional
Seek emergency help immediately if you have chest pain. In patients whose chest pain signals heart attack, prompt treatment can limit heart muscle damage.
Do not waste precious time hoping that your chest pain disappears.
In people with CAD, the outlook depends on many factors.
People with stable angina who are taking medications regularly, eating properly and exercising as instructed by their doctors, generally remain active and have an excellent prognosis.
The prognosis for heart attacks when people reach the emergency room promptly has improved dramatically. However, many people still die before reaching the hospital. This is why it is so important to prevent CAD.
American Heart Association (AHA)
National Heart, Lung, and Blood Institute (NHLBI)
American College of Cardiology