Coronary artery disease (CAD), the most common type of heart disease, refers to the narrowing of arteries that supply blood to the heart due to a build-up of a sticky substance called plaque. The heart muscle does not get enough oxygen when heart arteries are narrowed. If the heart is starved of oxygen, chest pain (angina) occurs. A piece of the plaque may break off and cause the body to form a clot on the damaged artery, cutting off oxygen to the heart and leading to a heart attack. A heart attack is medically referred to as a myocardial infarction (MI) and is one of the leading killers of both men and women.

Many of these deaths can be prevented because some risk factors for CAD are controllable. These controllable risk factors include high blood pressure, high blood cholesterol, and diabetes. There are other controllable risk factors related to lifestyle, such as not smoking, maintaining a healthy weight, eating a healthy diet, reducing alcohol consumption, and being physically active.

Although medical treatments for heart disease have come a long way, controlling risk factors remains the key to preventing illness and death from CAD.

A low supply of oxygen in the heart is most often caused by atherosclerosis, also called "hardening of the arteries." In this condition, fatty deposits called plaques form in the linings of the blood vessels. The plaques make the arteries narrower as they build up, and less blood is able to get through to the heart, depriving it of oxygen.

Atherosclerosis is often the result of too much "bad" cholesterol (low density lipoprotein, or LDL) and triglycerides circulating in the bloodstream.

You are at risk for developing atherosclerosis and CAD if you:

• have high levels of "bad" (LDL) cholesterol
• low levels of "good" (HDL, or high density lipoprotein) cholesterol
• have high blood pressure
• are a smoker
• have diabetes
• have an unhealthy diet
• lead a sedentary lifestyle
• are overweight (particularly if you are obese in the torso or have a large waist circumference)
• have a family history of heart disease
• consume alcohol excessively

Occasionally, a genetic condition can cause atherosclerosis, leading to heart disease.

In Canada, men are twice as likely to develop coronary artery disease than women. 

Some people with CAD might have no symptoms until the disease is severe enough to cause chest pains, or angina pectoris (angina comes from the Greek word for "strangling").

Stable angina is often the first sign that a person has CAD. Chest pain or discomfort occurs with activity and is relieved by rest. With unstable angina, symptoms become less predictable and can occur when you are at rest. This indicates rapid progression of CAD and higher risk of a heart attack and requires that you see a doctor immediately.

Some symptoms of angina include:

• tightness or a squeezing sensation across the chest
• burning or pressure beneath the breast bone
• pain or ache radiating to the shoulders, jaw, arms, throat, neck, or upper abdomen
• fatigue
• sweating
• weakness
• shortness of breath
• lightheadedness

If a plaque lining a blood vessel ruptures, it may completely block an area of the heart from receiving the oxygen-rich blood supply it needs. The starved cells in that area will then die, resulting in a heart attack.

The symptoms of a heart attack are similar to those of angina, but much stronger.

Men will often feel:

• constant pain in the middle of the chest that may radiate to the neck, jaw, left shoulder, or arm
• tightness or squeezing in the chest
• a sensation of "heaviness" or heavy indigestion
• sweating, nausea, and vomiting
• shortness of breath
• anxiety, fear, or denial

In women, the main symptoms can be similar to men but may also include:

• shoulder, neck, or back pain
• feeling a sharp pain on breathing in cold air
• unusual fatigue or weakness

It's very important to immediately call 9-1-1, or get medical help as quickly as possible if you feel you have the symptoms of a heart attack.

An electrocardiogram (ECG) detects abnormal electrical cardiac charges. In someone who has had heart damage, the electrical signals that keep the heart beating change as they pass through damaged tissue. This can be detected and measured on an ECG.

An exercise electrocardiogram (or stress test) checks your heart for changes during periods of activity, and it can also show if the coronary arteries are too narrow. An exercise stress test is performed on a treadmill or a stationary bicycle while hooked up to an ECG. A thallium scan allows imaging of blood flow in the heart during exercise. This involves injecting a very small dose of radioactive substance into the bloodstream, which is followed through the heart by a special camera.

With angina, abnormalities in the ECG may only occur while the person is having an angina attack. Some people have "silent angina," where even an attack brings no symptoms. To detect this, you may be asked to wear a monitor for 24 hours. The ECG tape is analysed for irregularities, and then compared with a detailed diary, in which you record your daily activities and any unusual symptoms.

Coronary angiography (or arteriography) is a test used to explore the coronary arteries. A fine tube (catheter) is put into an artery of an arm or leg and passed through the tube into the arteries of the heart. The heart and blood vessels are injected with contrast dye, which is then filmed with an X-ray while the heart pumps. The picture that is seen, called an angiogram or arteriogram, will show problems such as a narrowing or blockage caused by atherosclerosis.

Your doctor may prescribe any of these medication treatments:

• Cholesterol-lowering medications can reduce the levels of "bad" (LDL) cholesterol in your blood while increasing the levels of "good" (HDL) cholesterol. Your medication will be chosen based on the amounts of various cholesterol types found in your blood.
• Blood pressure reducing agents can lower your risk of heart attack dramatically if you have high blood pressure. These medications come in several types, and your doctor will advise which medication is best for you.
• Antiplatelet medications prevent clots from forming. In some cases your doctor may recommend taking acetylsalicylic acid* (ASA) to reduce the chances of having a heart attack.
• Beta-blockers, calcium channel blockers, and nitroglycerin-type medications are the three main classes of medications used to treat stable angina over time. Medications that treat angina help reduce the heart's workload.

When aggressive treatment is required, your doctor may recommend a procedure to help improve blood flow. Some options include:

• Percutaneous coronary intervention. This is also known as an angioplasty with stent. In this non-surgical procedure, your doctor uses a thin tube (catheter) to place a mesh tube, or stent, in the narrowed artery. The stent keeps the blood vessel open to allow blood to flow. Some stents also release medication that keeps the artery from narrowing.
• Coronary artery bypass surgery. This procedure involves using a blood vessel from another part of the body to create a "bypass" or detour around the blocked or narrowed coronary arteries. Because this requires open heart surgery, this procedure is usually for people who have many blocked arteries or whose blocked arteries are in a place that's difficult to place a stent.
• Keyhole surgery and robotic procedures. These are newer, less invasive techniques recently made available from improvements in surgical technology. With keyhole surgery, chest incisions can be much smaller, and the operating times are usually much shorter. Robotic procedures involve pencil-sized robotic arms that hold specifically designed surgical instruments. Surgeons can watch a magnified 3D image of the operation, while the robotic arms mimic the movements of the surgeon's hands.

Getting medication treatment isn't the only way to combat coronary artery disease. Here are a few heart-healthy tips to help prevent CAD:

• Quit smoking. If you smoke, quitting is the most important step you can take to quickly and significantly reduce your risk of developing CAD. 
• Eat a healthy diet. It should be low in salt and fat (less than 30% of total calories) and high in fibre, fresh fruits, whole grains, legumes (beans), nuts, and seeds. Avoid trans fat and limit saturated fat, fried foods, and refined carbohydrates. Losing weight through eating healthy can also offset the risks associated with CAD.
• Drink alcohol moderately. Have no more than:
• 2 drinks per day (or no more than 3 drinks on special occasions) to a maximum of 10 drinks per week for women
• 3 drinks per day (or no more than 4 drinks on special occasions) to a maximum of 15 drinks per week for men
• Get your blood sugar under control. Diabetes increases the risk of CAD, especially if blood sugar levels are not properly controlled. Make sure you are monitoring your blood sugar levels every day and following your diabetes treatment plan.
• Have your cholesterol levels checked regularly. Most healthy adults should have this done every 4 to 6 years. Everyone over 40 years of age, as well as anyone who has gone through menopause, should have their cholesterol levels monitored regularly, even if they do not have CAD or a history of high cholesterol. Adults of any age should get their cholesterol levels checked if they have certain risk factors for heart disease (e.g., high blood pressure, diabetes, family history of CAD, or conditions that increase their risk, such as arthritis). Depending on your risk for heart disease, your target cholesterol levels will differ.
• Get regular exercise. Along with reducing the chances of having a heart attack, regular physical activity lowers the heart rate, improves cholesterol levels, and helps control high blood pressure. It can also help you lose weight. Consult your doctor before starting an exercise program, especially if you have any other medical conditions.
• Manage your stress levels. This will also benefit those with high blood pressure. As well, it reduces the levels of some hormones that may increase the risk of having a heart attack.