Coronary heart disease
Coronary heart disease occurs when the coronary arteries which deliver oxygen to the heart muscle become narrowed or blocked by plaques. Plaques are formed by a gradual build up of fat/cholesterol within the artery wall (a process known as atherosclerosis) which reduces blood flow to the heart muscle. If the plaque build-up is only mild, there may be no signs or symptoms. However, increased activity or stress may produce symptoms such as a feeling of pressure or tightness in the chest.
This may be a signal that the heart muscle is not receiving an adequate supply of oxygen. When the blood supply to the heart muscle is severely reduced, chest pain (angina), heart attack (myocardial infarction) or rhythm disturbances (arrhythmia) may occur. A heart attack is usually the result of a completely blocked coronary artery. This may cause irreversible damage to the heart muscle.
Coronary heart disease is also known as atherosclerotic heart disease, ischaemic heart disease and coronary artery disease.
General heart information
The heart is a muscle that pumps blood to all parts of the body. A healthy heart in an adult is usually the size of a clenched fist. It is divided into four chambers - left and right atrium, left and right ventricle. When the heart chambers contract, blood is pumped out of the heart through the aorta (the main artery from the heart) carrying oxygen and nutrients to the rest of the body.
The heart itself also needs oxygen to function. It’s the job of the coronary arteries to deliver oxygen-filled blood to the heart muscle. There are three major coronary arteries that branch into smaller arteries to do this job.
Coronary heart disease risk factors
There are many risk factors related to coronary heart disease. Some of these risk factors can be controlled through lifestyle changes and/or medications, while others cannot.
Controllable factors include:
- High blood cholesterol
- High blood pressure
- Physical inactivity
- Poor diet.
Non-controllable factors include:
- Personal history of heart disease
- Male gender
- Family history of heart disease
In New Zealand, coronary heart disease is the most common form of cardiovascular disease (coronary heart disease, stroke and blood vessel disease). Each day approximately 17 New Zealanders – one every 90 minutes – die as the result of coronary heart disease. It is the leading single cause of death in New Zealand, accounting for almost one quarter of all deaths.
The condition affects men more commonly than pre-menopausal women. However, after menopause, the incidence in women increases to be virtually the same as men. Men older than 45 years and women older than 55 years are at increased risk.
Overall, Maori and Pacific Island New Zealanders are more at risk of suffering from coronary heart disease.
If coronary heart disease is suspected a thorough physical assessment will be undertaken. An assessment of risk factors and current symptoms will also be made. Additional tests to assist with making an accurate diagnosis may also be undertaken. Tests may include:
These check the levels of such things as electrolytes, blood cells, clotting factors and hormones in the blood. Specific enzymes and proteins that can indicate problems with the heart will be tested for.
A resting ECG records the electrical activity of the heart when at rest. This may show changes that indicate the heart muscle is not receiving enough oxygen. Electrical activity of the heart will be recorded using electrodes placed on the arms, legs and chest.
Exercise ECG/ Exercise Tolerance Test (ETT)
This test is designed to assess the heart’s response to exercise and stress. It involves walking on an exercise treadmill or riding an exercise bike for up to 12 minutes at varying degrees of speed and incline. Continuous ECG and blood pressure recordings are taken and symptoms of coronary artery disease such as shortness of breath, and pain in the chest, jaw or arm will be noted. A doctor and an ECG technician will be present at all times. Results based on the ECG, blood pressure recordings and any symptoms experienced can indicate whether coronary heart disease is present.
Echocardiography is the use of ultrasound waves to display the movements of the heart as it beats. The image produced allows doctors to measure precisely the dimensions of the heart and assess any damage to the heart muscle.
This test, also referred to as a “stress echo”, involves the administering of certain medications into the blood stream through a drip in the hand or arm while the echocardiogram is being performed. These medications stimulate the heart and mimic the effect of exercise. This test is often used for people who are unable to exercise for medical reasons.
An angiogram (also known as cardiac catheterisation) is a diagnostic test that involves inserting a small, flexible tube (catheter) into an artery in the arm or groin. The catheter is threaded up through the artery, into the aorta and is positioned at the entrance to the coronary arteries. A specialised x-ray dye containing iodine is injected through the catheter and into the coronary arteries. The x-ray dye is able to be seen on an x-ray screen and produces an outline of any narrowing or blockages in the arteries.
Heart function and efficiency can also be assessed during this test.
This computerised x-ray technology uses multiple cross sectional x-ray images to create detailed three-dimensional pictures of the heart. A contrast dye is injected through a vein in the arm and x-rays are taken while the person is lying on a specialised x-ray table. The contrast dye briefly fills the arteries of the heart and the heart chambers, enabling them to be seen on the x-ray pictures.
The three-dimensional pictures can indicate any narrowings, fat deposits and calcium in arteries. Information can also be gained about the heart muscle function and the heart valves.
This is a non-invasive test that takes approximately ten minutes to perform, with a total hospital stay of only one to two hours.
Nuclear Isotope Imaging
Nuclear isotope imaging involves the injection of a radioactive compound called a tracer into the bloodstream. Computer generated pictures of the tracer are then taken as it moves through the heart. From these images it is possible to assess how the heart is functioning and detect any narrowed or blocked blood vessels. Nuclear isotope imaging techniques include: multigated radionuclide angiography (MUGA) and single photon emission computed tomography (SPECT).
Depending on test results, various treatment options will be considered. Treatment may include medication, coronary angioplasty, or coronary artery bypass surgery (sometimes abbreviated to CABG) with or without coronary artery stenting. Treatment is aimed at reducing or eliminating symptoms thus reducing the risk of having a heart attack.
Classes of medications commonly used to treat coronary heart disease include:
- Beta Blockers - These medications slow the heart rate and reduce the blood pressure thus reducing the heart’s workload.
- Nitrates - These medications dilate (widen) the arteries making it easier for blood to be pumped through.
- Calcium Channel Blockers/Calcium Antagonists - These medications work by slowing the entry of calcium into the heart and blood vessel walls. This relaxes the arteries causing them to dilate. This lowers the blood pressure and reduces the heart’s workload.
- ACE Inhibitors - These medications prevent the constriction of peripheral blood vessels thereby reducing the pressure against which the heart must pump.
Aspirin is also usually prescribed as this discourages the formation of blood clots.
Some people require medication to lower their blood cholesterol levels and reduce plaque build-up in the arteries. Common cholesterol lowering medications include Lipex, Bezalip and Lipitor.
Coronary Angioplasty and Stenting
Coronary angioplasty is a non-surgical technique used to widen narrowed coronary arteries. The procedure is similar to an angiogram and involves inserting a balloon-tipped catheter into a narrowed coronary artery. As with the angiogram the catheter will be inserted through an incision in the groin or arm. The patient will be awake but sometimes mildly sedated for the duration of the procedure. The balloon is positioned at the site of the narrowing in the coronary artery. It is then inflated, compressing the plaque and slightly stretching the artery wall. This increases the diameter of the artery and therefore improves the flow of blood to the heart. Coronary angioplasty has a high success rate, but it is not an appropriate treatment for all people with coronary artery disease.
Stenting is the process in which a stent (a metal mesh tube) is placed in the narrowed artery during the coronary angioplasty procedure and acts as a scaffold to keep the artery open. Most coronary angioplasties now involve the placing of a stent as these have been shown to reduce the rate at which coronary arteries re-narrow by up to 50%. Stenting may not be required in all situations. Their use will be determined by the location and severity of narrowing and the initial result of the balloon inflations. Some stents, called drug eluting stents, are coated with a medication that further reduces the risk of re-narrowing of the artery.
Coronary Artery Bypass Surgery (CABG)
A coronary artery bypass involves using a blood vessel taken from elsewhere in the body to restore blood flow beyond the area of narrowed artery. This is done by grafting one end of the blood vessel to the blocked coronary artery below the blockage or narrowing and the other end to the aorta, thus “bypassing” the blockage. Chest wall arteries, arteries from the forearm, and veins from the legs can be used as graft vessels. The operation takes approximately three to four hours and the average length of stay in hospital is five to seven days. The breastbone is cut during the procedure and can take up to eight weeks to heal. Patients will be advised to limit activities during this time.
Coronary Artery Bypass Surgery (CABG)
Graphic courtesy of A. Bonsall and MedicineNet.com
Reducing the Risk
There are a number of steps that can be taken to reduce the risk of developing coronary heart disease. These include:
- Eating a healthy, balanced diet
- Limiting alcohol
- Not smoking
- Undertaking regular physical exercise – 30 minutes most days of the week
- Maintaining a healthy body weight
- Maintaining healthy blood cholesterol levels
- Effectively treating medical conditions such as diabetes and high blood pressure
- Being aware of risk factors.
Self-awareness and education in order to minimise risk factors is important in helping to prevent and control coronary heart disease. Additional information about hert health is available in our Southern Cross Health Test (link to SCHT section home page) section.
Because coronary heart disease is the major cause of illness and death in New Zealand, refinements and new approaches to treatments are constantly being attempted and investigated. This research is recognised internationally. For further information on coronary heart disease please contact a doctor or the National Heart Foundation of NZ.
The National Heart Foundation of New Zealand (National Head Office)
PO Box 17 160
Phone: (09) 571 9191
Fax: (09) 571 9190
There are branches in most New Zealand regions. Please consult a local phone book for contact details.
De Milto. L; Odle. T. G (2006) Coronary Artery Disease. The Gale Encyclopaedia of Medicine. Third Edition. Jacqueline L. Longe, Editor. Farmington Hills. MI. Thompson Gale.
MedicineNet (2006) Coronary angioplasty. Foothill Ranch: MedicineNet Inc www.medicinenet.com/Art.asp?li=MNI&ArticleKey=271
National Heart Foundation of New Zealand (2007) General Statistics. National Heart Foundation of New Zealand. Wellington. www.nhf.org.nz/index.asp?pageID=2145831169
National Heart Foundation of New Zealand (2007) Tests and Treatments. National Heart Foundation of New Zealand. Wellington.
Last Reviewed – 27/03/07
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