Coronary Artery Disease

Coronary artery disease (CAD), also known as coronary heart disease and ischemic heart disease, is a special type of atherosclerosis that occurs in the coronary arteries. The coronary arteries, which supply most of the tissues of the heart, become narrowed with plaque and this can lead to blood clot formation (thrombosis). Blood clots can partially or completely block blood flow. Reduced blood flow to the heart muscle can cause angina (chest pain or discomfort usually relieved by rest) or a heart attack (myocardial infarction). It is also possible to develop shortness of breath or extreme fatigue on exertion due to a reduced blood flow to the rest of the body secondary to reduced flow to the heart muscle. Ultimately, coronary artery disease may weaken the heart muscle extensively, as it is deprived of oxygen and other nutrients, and furthermore lead to heart failure and arrhythmias (abnormalities in the rhythm or speed of the heartbeat).

Causes and Associated Risk Factors
Coronary artery disease usually begins with any damage to the inner layer of a coronary artery that may lead to the accumulation of plaque. This can start as early as childhood at times. The initial insult to the inner lining of the coronary artery may be as a result of:
· Diabetes
· High blood pressure
· High cholesterol
· Radiation therapy to the chest, which may be used for certain types of cancers
· Smoking
Risk factors for coronary artery disease include:
· Age - the older you are, the greater the risk.
· Diabetes - high blood sugar can encourage plaque formation.
· Gender - males are more susceptible but the risk for post-menopausal women is high.
· Family history - a family history of heart disease is associated with a higher risk for developing CAD, especially if the parent developed it at an early age.
· High cholesterol levels - this increases the risk for plaque formation and eventually atherosclerosis.
· High blood pressure - this can lead to the hardening and thickening of the arteries, eventually narrowing the space through which blood flows.
· High stress - unrelieved stress can cause damage to arteries as well as worsen other risk factors for CAD such as high blood pressure.
· Obesity - excess weight can worsen other factors such as high cholesterol levels and diabetes.
· Physical inactivity - lack of exercise can contribute to the development of CAD and may be associated with some of the other risk factors, for instance obesity.

Research is also being done on these possible risk factors:
1. C-reactive protein - produced by the liver in response to injury or infection. It plays a central role in atherosclerosis.
2. Fibrinogen - a protein present in the blood which is activated in response to injury or inflammation and plays an important role in blood clotting.
3. Homocysteine - an amino acid (basic unit of proteins) used to make certain proteins and to build and maintain tissue. Excessive levels of this amino acid may increase the risk of CAD and other cardiovascular diseases.
4. Apoprotein A - a structural component of high density lipoprotein (HDL or ‘good’ cholesterol). It may disrupt the body’s ability to dissolve blood clots. High levels of apoprotein A may be associated with an increased risk for cardiovascular diseases, including CAD and heart attack.

Diagnosis
One or more of the following diagnostic tests may be performed to determine whether coronary artery disease is evident:
· Blood tests - check the levels of certain fats, cholesterol, sugar and proteins in the blood.
· Cardiac catheterization - a long, thin, flexible tube called a catheter is placed into a blood vessel in the arm, groin (upper thigh) or neck and directed towards the coronary arteries. This is used with coronary angiography.
· Chest X-ray – gives a picture of the organs and structures inside the area of the chest.
· Coronary angiography – uses dye and special x-rays to show the insides of the coronary arteries.
· Electrocardiogram (ECG/EKG) - measures the electrical activity of the whole heart. Certain patterns may suggest CAD is likely. Other signs such as a previous heart attack may also be detected.
· Echocardiography - uses sound waves to create a moving picture of the heart and can identify areas of poor blood flow to the heart, whether the heart muscle isn’t contracting properly and there was previous injury to the heart caused by poor blood flow.
· Electron-Beam Computed Tomography (EBCT) – finds and measures calcium deposits in and around the coronary arteries. This test is not routinely done to diagnose coronary artery disease because of uncertainty or its accuracy.
· Magnetic Resonance Angiogram (MRA) – uses magnetic resonance imaging (MRI) technology to check for areas of narrowing or blockages. The details are not as clear as those from coronary catheterization.

Treatment
Medical treatment for coronary artery disease may consist of medicines and medical procedures. Lifestyle changes are also very important for the treatment process. Treatment seeks to:
· Lower the risk of blood clot formation.
· Reduce any risk factors in order to delay, stop or reverse the progression of plaque build-up.
· Relieve any related symptoms.
· Prevent complications associated with CAD.
· Widen or bypass clogged arteries.

Medicines may be prescribed to:
· Decrease the workload on the heart
· Decrease the possibility of having a heart attack or sudden death
· Lower cholesterol levels and blood pressure
· Prevent blood-clotting
· Prevent the need for medical procedures to treat CAD.
Drugs/medicines used to treat CAD include:
· Angiotensin-converting enzyme (ACE) inhibitors – decrease blood pressure and may help prevent CAD progression.
· Aspirin – can reduce the blood’s tendency to clot but should not be taken if you have a bleeding disorder orypu’re already taking another blood thinner.
· Beta-blockers – slow heart rate and decrease blood pressure while decreasing the heart’s oxygen demand
· Calcium channel blockers – relax the heart muscle that may surround coronary arteries and encourage the vessels to open, increasing blood flow to the heart. They may also control high blood pressure.
· Cholesterol-modifying medications – lower the amount of ‘bad’ cholesterol in order to decrease the primary material involved in the accumulation of deposits in the coronary arteries. For example: statins, niacin, fibrates and bile acid sequestrants.
· Nitroglycerin – can control chest pain and pressure by dilating (opening up) the coronary arteries and reducing the heart’s demand for blood.

The following medical procedures are usually opted for to treat severe forms of CAD:
· Angioplasty and stent placement – a long, thin tube (catheter) is inserted into the narrowed part of the affected artery. A wire with a deflated balloon is passed through the catheter to the narrowed area. The balloon is then inflated, compressing the deposits against the artery walls. A stent may be left in the artery to keep it open. Some stents release medication slowly to keep the artery open.
· Coronary artery bypass surgery – a graft is created to bypass (make an alternate pathway) coronary arteries using a vessel from another part of the body, e.g. a segment of the great sephenous vein of the lower limb, which does not possess valves to control blood flow. This allows blood to flow around the blocked or narrowed coronary artery. This procedure is usually only done when there are multiple narrowed coronary arteries, since open-heart surgery is required.