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Coronary Artery Disease

Definition

Coronary artery disease or CAD (also known as ischemic heart disease, coronary heart disease or heart disease), refers to abnormalities of the arteries that carry oxygen and other nutrients to the heart muscle.

Description

The heart is a muscle that pumps blood throughout the body. To function properly, the heart must receive oxygen. Oxygen is supplied to the heart by coronary arteries that wrap around the surface of the heart. CAD is generally due to the buildup of plaque or lesions in the coronary arterial walls (a process known as atherosclerosis). Plaque is composed of cholesterol-rich fatty deposits, collagen, other proteins and excess smooth muscle cells.

Atherosclerosis, which usually progresses very gradually over a lifetime, thickens and narrows the arterial walls, impeding the flow of blood. The resulting condition of inadequate blood supply is called ischemia.

When the heart muscle becomes ischemic, a person may experience angina pectoris (pain in chest), heart attack (sudden death of part of the heart muscle) or death.

Causes and Risk Factors

Risk factors are conditions that increase the risk of developing heart disease. Some can be controlled while others are uncontrollable. You are at risk for CAD if you:

Controllable factors:

1. have high blood pressure
2. have high blood cholesterol levels
3. have diabetes
4. smoke
5. are overweight
6. lead a sedentary lifestyle
7. have stress

Uncontrollable factors:

1. a family history of heart disease
2. being a male over 45 or a female over 55

Symptoms

CAD is a disease that progresses very slowly, often without symptoms. Unless the person is tested for the disease, the first sign that something is wrong may be an episode of angina pectoris or a heart attack.

The symptoms of angina pectoris are:

• Chest pain or a milder pressure, tightness, squeezing, burning, aching or heaviness in the chest, lasting between 30 seconds and five minutes. The pain or discomfort is usually located in the center of the chest, just under the breastbone, and may radiate down the arm (usually the left), up into the neck or along the jaw line. The pain is generally brought on by exertion or stress, and stops with rest. The amount of exertion required to produce angina is reproducible and predictable.
• Shortness of breath, dizziness or a choking sensation accompanying the chest pain
• A sudden increase in the severity of angina or angina at rest is a sign of unstable angina that requires immediate attention because a heart attack may occur shortly.
• Nausea
• Vomiting
• Profuse sweating

The symptoms of a heart attack:

• Sudden chest pain, ranging from a tight ache to an intense, crushing pain. This pain can last 30 seconds or longer. The pain or discomfort is usually located in the center of the chest (just under the breastbone) and may radiate down the arm (usually the left), up into the neck and along the jaw line. It may also be felt in the upper abdomen.
• A sense of tightness or "squeezing" in the chest
• Restlessness and apprehension
• Cold, clammy or pale skin
• Shortness of breath
• Dizziness
• Nausea
• Vomiting
• A loss of consciousness
• Profuse sweating

Diagnosis

CAD is diagnosed by taking a thorough patient history, performing a physical examination, an exercise electrocardiogram (ECG) or stress test, a coronary angiography, blood tests and a chest x-ray.

A stress test involves the use of a treadmill or stationary bike. Electrodes are placed on various parts of the chest and a blood pressure cuff is placed on the arm. While the person walks on the treadmill or pedals the bike, their heart rate, blood pressure and electrocardiographic tracings are monitored to see if there are signs of decreased blood flow. If the results of this test show an abnormal reading, the doctor will suggest a coronary angiography.

A coronary angiography is performed by inserting thin tubes (catheters) into the arteries of the leg or arm (called cardiac catheterization) and guiding them into the coronary arteries. Special dyes (visible on x-rays) can be injected into these arteries through the catheters to determine if blood flow is blocked.

Blood tests are given to evaluate cholesterol levels (one of the risk factors of CAD) to either rule out or confirm diabetes (another risk factor of CAD) and to analyze the thyroid hormone. An under- or over-active thyroid gland can produce heart abnormalities.

A chest x-ray is useful in identifying results of heart disease.

If needed, the doctor may perform a radionuclide scan or an echocardiogram. There are two types of radionuclide scans - a thallium exercise scan and a radionuclide angiogram.

The thallium exercise scan involves the injection of a small dose of radioactive isotope into a vein in the arm. While the patient is exercising, a special scanning device records a series of pictures of the locations of this isotope. Dark areas indicate impaired blood flow.

A radionuclide angiogram involves the injection of a small dose of radioactive isotope. The patient is placed on a table and asked to pedal a bike. Scans are made to locate the isotope in the region of the heart. An impaired expansion or contraction of the heart wall alerts the doctor of narrowed arteries.

An echocardiogram uses ultrasound to detect structural and functional abnormalities of the heart. When a portion of the heart muscle receives insufficient blood flow, it develops an abnormal contraction pattern.

Treatment

Although CAD can be a life-threatening condition, the outcome of the disease is in many ways up to the patient. Damage to the arteries can be slowed or halted with lifestyle changes, medication or surgical procedures, as listed below:

Lifestyle changes

These changes include smoking cessation, dietary modifications and regular exercise.

Medication

Medications are prescribed according to the nature of the person's CAD and other factors. The symptoms of angina pectoris can generally be controlled by beta-blockers, nitrates and calcium-channel blockers.

Beta-blockers (such as propranolol [Inderal] and metoprolol [Betaloc]) are used to slow the heart rate and allow the heart to get along with less oxygen. Nitrates (i.e., nitroglycerin) and calcium-channel blockers (such as diltiazem [Cardizem] and nifedipine [Procardia]) are used to relax and dilate the coronary arteries.

To decrease the risk of a heart attack, beta-blockers and thrombolytic drugs are prescribed. Thrombolytic drugs are used to dissolve blood clots. Thrombolytic drugs work by increasing the blood level of plasmin - an enzyme that dissolves fibrin (the main constituent of blood clots). The three thrombolytic agents approved for clinical use are streptokinase (Kabikinase, Streptase), urokinase (Abbokinase) and alteplase (Activase), a tissue-type plasminogen activator.

To reduce high blood pressure, doctors may prescribe beta-blockers, calcium-channel blockers, diuretics, vasodilators or angiotensin converting enzyme (ACE) inhibitors.

Diuretics or "water pills," such as hydroclorathyazide (Esidrix, Hydro-D, etc.), chlorathalidone (Hygroton) and chlorothiazide (Diuril), increase the elimination of salt and water through urination, thereby lessening blood volume and pressure.

ACE inhibitors (captopril (Capoten), enalapril (Vasotec) and lisinopril (Zestril)) lower blood pressure by blocking the production of a hormone known as angiotensin, which increases blood pressure.

Vasodilators relax the smooth muscle of the peripheral arteries, which causes them to dilate and so reduce the resistance to blood flow.

To reduce cholesterol, the doctor may prescribe HMG-CoA reductase inhibitors (also called statins) that lower cholesterol by interfering with its production in the liver and by boosting the removal of LDL from the blood. Pravastatin (Pravachol), lovastatin (Mevacor), simvastatin (Zocor) and fluvastatin (Lescol), are some of the cholesterol-lowering drugs currently prescribed.

Surgical and other invasive methods

Invasive surgical methods for treating CAD are required in cases where the left main coronary is blocked, multiple arteries are effected, the left ventricle of the heart is not functioning properly or with debilitating angina.

There are two types of procedures recommended for CAD: coronary artery bypass and coronary angioplasty (also called percutaneous transluminal coronary angioplasty - PTCA).

Coronary artery bypass surgery involves opening up the chest area and leg area and taking a short length of vein (usually from the thigh or lower leg) and using it to allow blood to bypass the blockage in a coronary artery.

PTCA involves insertion of a hollow, flexible tube (called a guide catheter) into a leg or arm artery whereby, with the use of x-ray image, the doctor guides the catheter into the narrowed coronary artery. A small catheter, with a balloon on the tip, is then inserted inside the guide catheter. When this catheter reaches the narrowed area, the balloon is inflated to reopen the artery. Newer methods, similar to PTCA, are being used. Using a tiny rotating blade, laser-assisted or stents to reopen the narrowed arteries have been successful.

Prevention

• Limit your consumption of red meat and increase your consumption of vegetables, fresh fruits, low-fat milk, grains, fish, poultry and folic acid enriched foods such as beans, spinach, peas and asparagus. The fat content in red meat is a high contributor to plaque in the arteries.
• Know your cholesterol, LDL, HDL and triglyceride levels.
• The level of cholesterol in your blood is a good indicator of the health of your heart and blood vessels. Generally, the higher your cholesterol level, the greater your risk of heart disease. LDL stands for low-density lipoprotein. LDLs carry cholesterol around the body. LDLs deposit cholesterol in blood vessels where they can eventually build up and restrict blood flow. The more LDLs you have, the higher your risk factors for heart disease. HDL stands for high-density lipoprotein. HDLs remove cholesterol from artery walls and carry it to the liver, which breaks it down. Triglycerides are a type of fat present in foods and manufactured in the liver. The higher your triglyceride level, the greater your risk of heart disease.
• Increase levels of physical activity. Even a modest amount of activity each day will lower your LDL cholesterol and raise your HDL cholesterol. Exercise also improves your heart's pumping efficiency, benefits your circulation and increases your overall strength and endurance.
• Watch your weight. Obesity raises triglyceride levels, which in turn promotes heart disease.
• Know your family's history of heart conditions. A family history of obesity, diabetes, heart attack, stroke or high blood pressure, increases your risk of heart disease, so consult a cardiologist before the age of 45 for males and 55 for females.
• Pay attention to the pain. If you feel your vitality generally slipping, have a checkup. If you are having chest pains, go to the nearest Emergency Room.
• Reduce your stress.
• Don't smoke and limit the amount of alcohol you consume.
• Consider regular low doses of aspirin.

Questions to Ask Your Doctor

How serious is the condition?

Is the condition serious enough for invasive methods?

If so, do you recommend coronary artery bypass surgery or PTCA?

If surgery is done, will it have to be done again?

Am I a candidate for a heart attack, even after taking medication or having the procedure done?

If my lifestyle is changed (i.e., exercise, proper diet, losing weight) will this condition reverse itself?

Can you provide me with advice on how to change my behaviors or direct me to someone who can?