Coronary heart disease occurs when the coronary arteries which deliver oxygen to the heart muscle become narrowed or blocked as a result of the build up of fat/cholesterol within the artery wall.
If the build-up is only mild, symptoms may include a feeling of pressure or tightness in the chest at times of increased activity or stress. When the blood supply to the heart muscle is severely reduced, chest pain (angina
), heart attack (myocardial infarction)
or rhythm disturbances (arrhythmia) may occur.
Causes and risk factors
The heart is a muscle that pumps blood to all parts of the body. 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.
Coronary heart disease is also known as atherosclerotic heart disease, ischaemic heart disease and coronary artery disease. Its the result of the narrowing or blockage of coronary arteries by plaque formed by fat/cholesterol on the artery walls (a process known as atherosclerosis).
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:
Non-controllable factors include:
- Family history
- Medical history.
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. This will include an assessment of risk factors and current symptoms. 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, to view the structures of the heart (such as the heart valves), and to 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 wrist 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 (with or without coronary artery stenting), or coronary artery bypass surgery (sometimes abbreviated to CABG). Treatment is aimed at reducing or eliminating symptoms andreducing 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 will also be prescribed (unless there's amedical reason not to) as it helps to prevent the formation of blood clots.
Some people require medication to lower their blood cholesterol levels, thereby reducing plaque build-up in the arteries and reducing the risk of having a heart attack. Common cholesterol lowering medications include Lipex and Lipitor.
Coronary Angioplasty and Stenting
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 an angiogram the catheter will be inserted through an incision in the groin or wrist. 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.
Virtually all angioplasties also involve the placement of a stent. A stent is a small mesh tube that is placed in the narrowed coronary artery during the angioplasty procedure, acting as a scaffold to keep the artery open. The stent is mounted over the catheter’s balloon, so that when the balloon is inflated in the narrowed section, the stent opens. The balloon is then deflated and removed, leaving the expanded stent in place.
The use of stents has been shown to significantly reduce the rate at which coronary arteries re-narrow. The majority of stents are made of metal, however some bio-absorbable stents made of a dissolvable polymer are also now in clinical use. Most stents are coated with a medication that further reduces the risk of re-narrowing of the artery. These are known as drug-eluting stents.
A medication called clopidogrel is usually prescribed after the stenting procedures. This, in combination with aspirin, is recommended to be taken for a period of time (usually 6 months) after stent implantation. Once the clopidogrel is stopped, aspirin will need to be continued for life.
Coronary angioplasty and stenting has a high success rate but it is not an appropriate treatment for all people with coronary artery disease. If the narrowings in the coronary arteries are numerous and severe, surgery may need to be considered.
Coronary Artery Bypass Surgery (CABG)
Coronary artery bypass surgery 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.
CABG graphic courtesy of A. Bonsall and MedicineNet.com
There are a number of steps that can be taken to prevent or reduce the risk of developing coronary heart disease. These include:
Self-awareness and education in order to minimise risk factors is important in helping to prevent and control coronary heart disease.
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 Heart Foundation of New Zealand (National Head Office)
Phone: (09) 571 9191
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 (2011) Heart Disease. Foothill Ranch: MedicineNet Inc
Heart Foundation of New Zealand (2013) General Statistics. Heart Foundation of New Zealand. Auckland. http://www.heartfoundation.org.nz/know-the-facts/statistics
Heart Foundation of New Zealand (2013) Treatments. National Heart Foundation of New Zealand. Wellington. http://www.heartfoundation.org.nz/know-the-facts/treatments
Last Reviewed – 26 June 2013